Galloper Wind Farm Project Environmental Statement - Chapter 11: Offshore Ornithology October 2011 Document Reference – 5.2.11
Galloper Wind Farm Limited
Document title Galloper Wind Farm Project Environmental Statement - Chapter 11: Ornithology Document short title Galloper Wind Farm ES Document Reference 5.2.11 Regulation Reference APFP Regulations, 5(2)(a) Version 4 Status Final Report Date September 2011 Project name Galloper Wind Farm Client Galloper Wind Farm Limited Royal Haskoning 9V3083/R01/303424/Exet Reference
Drafted by Jenifer Snowball
Checked by Rob Staniland & Peter Gaches Date/initials check RS / PG 27.09.2011 Approved by Martin Budd Date/initials approval MB 25.10.2011 GWFL Approved by Kate Harvey (GWFL) Date/initials approval KH 01.11.2011
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CONTENTS
Page
11 OFFSHORE ORNITHOLOGY 1 11.1 Introduction 1 11.2 Guidance and Consultation 1 11.3 Methodology 11 11.4 Description of the Existing Environment 42 11.5 Assessment of Impacts - Worst Case Scenario 106 11.6 Assessment of Impacts during the Construction Phase 117 11.7 Assessment of Impacts during the Operational Phase 136 11.8 Potential Impacts during the Decommissioning Phase 176 11.9 Inter-relationships 177 11.10 Cumulative Impacts 179 11.11 Transboundary Effects 211 11.12 Monitoring 211 11.13 Summary 212 11.14 References 238
Technical Appendix 11.A Ornithological Technical Report
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11 OFFSHORE ORNITHOLOGY
11.1 Introduction
11.1.1 This Chapter of the Environmental Statement (ES) describes the existing environment with regard to offshore ornithological interest within the Galloper Wind Farm (GWF) site in the context of the wider regional study areas of the Outer Thames Estuary and southern North Sea.
11.1.2 The assessment serves to characterise the distribution, abundance and behaviour of ornithological species known to occur, or which have been recorded within the study area and wider region through site-specific boat- based and aerial seabird surveys. Through desk-based research, the subsequent assessment presents the potential impacts of construction, operation and decommissioning of the GWF project on the ornithological assemblage present, in particular species of conservation concern.
11.1.3 For the purposes of the Infrastructure Planning (Applications: Prescribed Forms and Procedure) Regulations 2009, Figures 11.5 and 11.6 taken together with this Chapter, fulfil the requirements of Regulation 5(2)(l) in relation to the effects of the proposed development on offshore ornithology.
11.2 Guidance and Consultation
Legislation, policy and guidance 11.2.1 National Policy Statements (NPS) provide the primary basis on which the Infrastructure Planning Commission (IPC) is required to make its decisions. In preparing this Chapter the following NPS’s are of relevance to offshore ornithology:
Overarching NPS for Energy (EN-1); and NPS for Renewable Energy Infrastructure (EN-3)
11.2.2 The specific assessment requirements for offshore ornithology, as detailed within the NPSs, are repeated in the following paragraphs. Where any part of the NPS has not been followed within this assessment, it is stated within in the ES why the requirement was not deemed relevant or has been met in another manner.
11.2.3 Generic biodiversity considerations are provided within Section 5.3 of EN-1 and re-iterated in Paragraphs 2.6.58 to 2.6.71 of NPS EN-3. The following paragraphs provide detail from NPS EN-3 (June 2011), which contains specific requirements for the assessment of impacts on offshore ornithological species. Included within the stated specific requirements are references to the relevant section of this Chapter, where the concern has been addressed.
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11.2.4 In relation to offshore ornithology, Section 2.6.101 of the NPS states that:
“Offshore wind farms have the potential for the following effects on ornithology: Collisions with rotating blades; Direct habitat loss; Disturbance from construction activities such as movement of construction/decommissioning vessels and piling; Displacement during the operational phase, resulting in loss of foraging/roosting area; and Impacts on bird flight lines (i.e. barrier effect) and associated energetic expenditure for commuting flights between roosting and foraging areas.” (Sections 16.6 to 16.10).
11.2.5 The assessment requirements for ornithology are set out in Paragraphs 2.6.102 to 2.6.105 states that:
11.2.6 “The scope, effort and methods required for ornithological surveys should have been discussed with the relevant statutory advisor. (Section 11.2).
11.2.7 Relevant data from operational offshore wind farms should be referred to in the applicant’s assessment. (Section 11.3).
11.2.8 It may be appropriate for assessment to include collision risk modelling for certain species of birds. Where necessary, the assessments carried out by applicants should assess collision risk using survey data collected from the site at the pre-application EIA stage. The IPC will want to be satisfied that the collision risk assessment has been conducted to a satisfactory standard having had regard to the advice from the relevant statutory advisor. (Section 11.3 and 11.7).
Policy and guidance 11.2.9 The following guidance documents have also been used to inform the assessment of potential impacts on offshore ornithology:
Guidance on the Assessment of Effects on the Environment and Cultural Heritage from Marine Renewable Developments. Produced by: The Marine Management Organisation (MMO), Joint Nature Conservation Council (JNCC), Natural England (NE), the Countryside Council for Wales (CCW) and Centre for Environment, Fisheries & Aquaculture Science (Cefas) (In draft, December, 2010); Guidelines for Ecological Impact Assessment in Britain and Ireland, Marine and Coastal (Institute for Ecology and Environmental Management (IEEM) (2010);
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Guidelines for data acquisition to support marine environmental assessments of offshore renewable energy projects. Draft for consultation. Cefas. Report reference: ME5403 – Module 15. Issue date: 10th March 2011; Nature conservation guidance on offshore windfarm development. A Guidance Note on the Implications of the EC Wild Birds and Habitats Directives for Developers; Undertaking Offshore Windfarm Developments (Defra, 2005); and Developing Guidance on Ornithological Cumulative Impact Assessment for Offshore Wind Farm Developers (COWRIE, 2009).
Legislation 11.2.10 Many species of seabird are protected under an assortment of national and international legislation, as summarised in Table 11.1.
Table 11.1 National and international legislation in relation to offshore avifauna
Legislation Protection Details
Directive Protection for all species The Directive provides a framework for the 2009/147/EC on of naturally occurring birds conservation and management of, and the conservation in the wild state in Europe. human interactions with, wild birds in of wild birds (The Applies to birds, their Europe. It sets broad objectives for a wide Birds Directive) eggs, nests and habitats. range of activities, although the precise legal mechanisms for their achievement are at the discretion of each Member State. See paragraphs 11.2.15 – 18 for further details.
The Wildlife and All wild birds, their nests Offences under the act include the Countryside Act and eggs are protected in intentional killing, injury or taking of any 1981 the UK under this act (a wild bird; intentionally taking or damaging wild bird is defined as any the nest of any wild bird whilst it is in use bird of a species that is or being built; intentionally taking or resident in or is a visitor to destroying the egg of any wild bird and the European Territory of intentionally or recklessly disturbing any any member state in a wild wild bird listed on Schedule 1 while it is state). nest building, or at a nest containing eggs or young.
The Countryside Part III of the act contains The Act enables the courts to impose and Rights of measures to strengthen heavier fines and prison sentences for
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Legislation Protection Details Way (CRoW) Act the enforcement of the virtually all offences. The act also puts a 2000; species protection duty on all ministers to further the purpose provisions of the Wildlife of conserving biological diversity in and Countryside Act 1981. accordance with the Convention on Biological Diversity 1992 (see the UK Biodiversity Action Plan in the following table entry)
The UK The UK BAP does not The UK BAP resulted from the UK’s Biodiversity afford specific legal commitment to the Convention on Action Plan (UK protection for species and Biological Diversity 1992, which came out BAP) habitats but it does of the Rio Earth Summit. highlight many species of conservation concern.
Natural Section 40 of the Act This duty extends to all public bodies the Environment and requires all public bodies biodiversity duty of section 74 of the Rural to have regard to CRoW Act, which placed a duty on Communities biodiversity conservation Government and Ministers. The list is used (NERC) Act 2006 when carrying out their to guide decision makers in implementing functions. Section 41 of their duty to have regard to the NERC requires the conservation of biodiversity in England. A Secretary of State to total of 56 habitats and 943 species publish a list of habitats (including birds) are included on the list, and species which are of these are the habitats and species that principle importance for have been identified as requiring the conservation of protection in the UK BAP. biodiversity in England.
The Habitats and Birds Directive 11.2.18 The most important wildlife legislation in relation to marine renewable energy and offshore avifauna is Directive 2009/147/EC (The ‘Birds Directive’) on the conservation of wild birds (the codified version of Council Directive 79/409/EEC as amended). In the UK, the provisions of the Birds Directive are implemented through the Wildlife and Countryside Act 1981 (as amended), The Conservation of Habitats and Species Regulations 2010 (as amended), referred to hereafter as ‘The Habitats Regulations’ (HR). The HR consolidate all the various amendments made to the Conservation (Natural Habitats, &c.) Regulations 1994 and implement the Habitats Directive and the Birds Directive as far as the limit of territorial waters (12 nautical miles). Beyond territorial waters, The Offshore Marine Conservation (Natural
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Habitats, &c.) Regulations 2007 (as amended) implement the Habitats Directive and Birds Directive in relation to marine areas where the UK has jurisdiction beyond 12 nautical miles to 200 nautical miles (or the median line).
11.2.19 Under Article 5 of Birds Directive 2009/147/EC, Member States are required to take the requisite measures to establish a general system of protection for all species of birds referred to in Article 1, prohibiting in particular the:
a) Deliberate killing or capture by any method; b) Deliberate destruction of, or damage to, their nests and eggs or removal of their nests; c) Taking their eggs in the wild and keeping these eggs even if empty; d) Deliberate disturbance of these birds particularly during the period of breeding and rearing, in so far as disturbance would be significant having regard to the objectives of this Directive; and e) Keeping birds of species the hunting and capture of which is prohibited.
11.2.20 Article 6 of The Habitats Directive requires that Member States ensure conservation measures are in place to appropriately manage Natura 2000 sites (Special Protection Areas (SPA) and Special Areas of Conservation (SAC)) and ensure appropriate assessment of plans and projects likely to have a significant effect on the integrity of these sites. Projects may still be permitted if there are no alternatives, and there are imperative reasons of overriding public interest. In such cases compensatory measures are necessary to ensure the overall coherence of the Natura 2000 network.
11.2.21 In addition, Article 4 of The Birds Directive requires Member States to identify and classify SPAs for rare or vulnerable species listed in Annex I of the Directive, as well as for all regularly occurring migratory species. The relevance of these to the GWF project is discussed further in Chapter 8 Nature Conservation Designations and The Habitat Regulations Assessment (HRA) Report.
Consultation 11.2.22 As part of ongoing consultation, the following key stakeholders were invited to respond to a scoping document produced as part of the EIA process (GWFL, 2010). Table 11.2 summarises issues that were highlighted by the consultees in the IPC Scoping Opinion (IPC, 2010) and the Section 42 consultation (July, 2011), indicating which sections of the Environmental Statement (ES) address each issue.
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Table 11.2 Summary of consultation and issues
Date Consultee Summary of issue Section where addressed 5th The JNCC The survey scope for baseline data collection at GWF in relation to the temporal and Section 11.3 November spatial extent of proposed aerial and boat-based surveys/ GGOWF construction activity. 2007
15th May The JNCC In this meeting the spatial and temporal specifications of the surveying methodology was Section 11.3 2009 discussed, alongside the format and timescales for reporting. It was concluded that two years of data would be required to inform the EIA.
17th The JNCC, NE, Data coverage: The suitability of the current data to inform the GWF EIA was Section 11.3 November Royal Society discussed. Two options were presented: 1) Use existing un-impacted data to inform the
2009 for the ES. This is only likely to be possible if JNCC and Natural England can be reassured that
Protection of the data coverage across the whole site is sufficient. 2) Continue surveying the GWF Birds (RSPB), site through 2009 and up to and including early June in 2010 and accept that the 2nd Marine year’s data will represent an impacted baseline for much of the site. (The JNCC &
Fisheries Natural England confirmed post-meeting (email from Lucy Greenhill on 08.11.2009) that Agency (MFA) they wished to see Option 2 taken forward for this project).
Collision Risk Modelling (CRM): The JNCC agreed that the proposed key species for inclusion within the collision risk model is acceptable and that there should be a range of Section 11.7 avoidance rates considered in the EIA (95%+).
January The JNCC and Further discussions on methodology. Better understanding of the latest status of the Section 11.3 2010 NE lesser black-backed gull population within the Alde-Ore SPA needed. Requirement for
Appropriate Assessment (AA) (under the HR) in relation to lesser black-backed gull
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Date Consultee Summary of issue Section where addressed interest from the Alde-Ore SPA is likely and will be confirmed through screening. Section 11.4-11.7 Requirement for AA for red-throated diver is unclear, further information is required. Chapter 8 and HRA Report Cumulative Impact Assessment (CIA) should encompass Round 2.5 projects, but
inclusion of Round 3 is still questionable due to lack of suitable data. Section 11.10
6th July The JNCC and At this meeting it was discussed that the baseline data collected at the GWF study area Section 11.3 2010 NE comprised one complete year of un-impacted data and a second year which was collected during construction at GGOWF and is therefore considered ‘impacted’. The approach to the CRM was discussed. It was agreed that initially the CRM should be based on only the first year of un-impacted baseline data.
July 2010 The JNCC and Potential environmental impacts on seabirds. Section 11.4 – 11.10 NE Requirement to produce density plots for key species to establish suitability of using data HRA Report from impacted years to inform the EIA.
Agreement that Round 2.5 and 3 projects are excluded from the GWF CIA based on current timeframes.
Likelihood for AA on lesser black backed gulls of the Alde-Ore Estuary SPA.
August The IPC Surveys should be relevant and up to date. Great care should be taken to ensure the Section 11.3 2010 (Scoping assessment if undertaken against a consistent baseline.
Opinion) Noise impacts should be assessed, specifically as a result of construction activities. Section 11.5
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Date Consultee Summary of issue Section where addressed
August The JNCC and Developer should ensure that there is as much confidence as possible in the data Section 11.3 and 11.4 2010 NE (Scoping collection which will inform the EIA process. Section 11.10 Opinion) Cumulative impacts must be thoroughly assessed (particularly in relation to London
Array and East Anglia ONE offshore wind farm). Section 11.4
A combination of methods are needed to understand both the distribution and
abundance of ornithological interest features, analysis of results from other investigations alongside existing survey information should be used to assist in the interpretation of the relevance of the area for bird species.
August RSPB (Scoping The environmental impact on birds and their habitats, specifically during construction. Section 11.5-11.10 2010 to Opinion) The effects of the early life stages for fishes may have lethal effects for bird life. The
March RSPB believe some comments within the Scoping Study are premature, and need
2011 – further research. HRA Report Potential impacts upon lesser black- backed gull populations highlighted.
17th The JNCC and At a meeting with NE and the JNCC, GWFL sought clarification on the approach to: Section 11.3 January NE Spatial/temporal coverage of datasets to inform EIA (including assessment of inter- 2011 annual variability);
Approach to Collision Risk Modelling (CRM); Section 11.7 and Technical HRA Screening: Population counts/ estimates and flight behaviour for lesser black- Appendix 11.A backed gull and red-throated diver at GWF. HRA Report
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Date Consultee Summary of issue Section where addressed
It was agreed that the following wind farm sites should be scoped into the CIA: London Section 11.10 Array II, Kentish Flats Extension Project, East Anglia ONE OWF.
15th April The JNCC and Based on key actions which came out of the meeting on 17.01.2011, GWFL prepared a Section 11.3 2011 NE Technical Note to provide information in support of its EIA strategy (GWFL, submitted to
the JNCC / Natural England on 18.02.2011). Comments were received on this note on
11.04.2011 and meeting was held on 15.04.2011 to refine the final EIA methodology in regard to the scope of datasets to inform the general EIA, and more specifically, the HRA Report CRM. Advice was also sought on the use of SPA citations and / or more recent count
data as part of the EIA and how to interpret Likely Significant Effect (LSE) within HRA.
The following actions are ongoing at the time of writing:
Refinements to be made to the CRM in terms of input parameters, such as species Section 11.7 biometrics, flight behaviour and avoidance rates; and
Sourcing the latest colony counts from the Alde-Ore SPA in relation to lesser black- backed gull
12th July The JNCC and Key actions which came out of the meeting at the JNCC Offices in Aberdeen: Section 11.3, 11.7 and 2011 NE Annex 4 of Technical GWFL to look at avoidance rates cited from other wind farm studies (as presented Appendix 11.A at the meeting) in more detail and communicate findings to the JNCC/NE
GWFL to resolve the quantity and quality of LBBG density estimates and/or processed CRM data from the other wind farms for cumulative/in combination
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Date Consultee Summary of issue Section where addressed assessment. Finalise a way forward to make collision risk estimates comparable across projects;
Next step for PVA: Produce a draft proposal to investigate a basic step-wise model- will include ongoing work from RPS to include assumptions so SNCAs can see what model is built from;
GWFL to decide how the Vantage Point survey outputs can be used to inform the assessment
14th July The JNCC, NE The GWF Section 42 consultation was submitted to the SNCAs and NGOs (including the and RSPB RSPB) on 6th June 2011. Subject to their review, advice on the key technical content
(Section 42) and critical EIA information was as follows:
CIA: Receptor led approach with relevant projects identified based on spatial extent of Section 11.10 impacts and sensitivity of receptors. GWFL to ensure that all available (relevant) datasets are used within the assessment of ornithological interests (such as EAOW ONE and Kentish Flats Extension). Should consent application dates slip then other data may
become available and should be included
Use of ‘impacted’ second year ornithological baseline and approach to statistical analysis and derivation of population and density estimates. Section 11.3
Consideration should also be given to indirect effects via impact to prey species, on Section 11.5, 11.6, 11.7, 11.9 specific forage fish and the flexibility individual bird species exhibit in their prey choice.
Approach to CRM, input parameters and use of the offshore Band Model (In draft).
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Date Consultee Summary of issue Section where addressed
EIA Methodology in relation to species sensitivity criteria and assessment of impact Section 11.7 magnitude. Section 11.3 Approach to assessment of migratory species (notably great skua and gannet) in
relation to maximum foraging ranges, connectivity with SPAs and CIA. Section 11.3, 11.7, 11.10 Further detail in relation to habitat utilisation, SPA connectivity and displacement effects Section 11.4 and Technical are particularly relevant for re-throated diver. Appendix 11.A Assessing the significance of impact due to attraction to lit structures. Section 11.7 Inter-relationships- specifically oil and gas exploration within the maximum foraging Section 11.9 and Technical range for species of principle concern, commercial fisheries and shipping activity. Appendix 11.A
18th RSPB At a meeting with GWFL, their ornithological advisors and the RSPB (full minutes August provided in Appendix A of the HRA Report), the project team covered the following
2011 areas:
EIA Methodology (temporal and spatial nature of datasets used to inform EIA, Section 11.3 approach to analysis and interpretation);
Approach to account for inter-annual variation and ‘impacted’ data; Section 11.7 and Technical Collision Risk Modelling for LBBG (desk-top review of avoidance rates and VP Appendix 11.A surveys)
Key impact scenarios (disturbance, displacement, barrier effects and collision
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Date Consultee Summary of issue Section where addressed mortality for red-throated diver, lesser black-backed gull and gannet); Section 11.6, 11.7 Approach for assessing impacts to migrants (notably Great skua);
CIA and inter-relationships; and Section 11.9 and 11.10
Approach to HRA HRA Report
1st JNCC At a telephone meeting between the GWF ornithological specialists at RPS and the Section 11.3, 11.7 and September JNCC, the following issues were discussed:
2011 Avoidance rates: RPS provided a summary of work undertaken to date in order to
establish accurate and realistic avoidance rates for gulls (literature review and VP
surveys). The JNCC confirmed that 98% was precautionary, but that this would only go up with more data, since this is so critical to mortality estimates.
PVA: Discussion of relative merits of stochastic vs. deterministic PVA models. RPS Annex 4 of Technical highlight that the justification for stochastic models instead of deterministic ones is much Appendix 11.A. reduced.
The JNCC confirmed that the question of whether an AA can be accepted based on possible management interventions was a grey area. This consideration will need to be addressed as part of the PVA input parameters.
Determining ‘significance’ of impact of extra mortality on different population trends was also discussed- the JNCC and NE await opportunity to see the latest PVA outputs as part of GWFL’s submission to the SNCAs on 9th September.
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Date Consultee Summary of issue Section where addressed
27th The RSPB, Provision of briefing on main bird issue (lesser black-backed gull) effects of the Galloper Section 11.7 and Annex 4 of September National Trust offshore wind farm and to obtain feedback on practicalities of enhanced land Technical Appendix 11.A. 2011 and Natural management at the Alde-Ore SPA. England At this meeting RPS, on behalf of GWFL, provided the Land Managers with a presentation overview of the GWF collision risk modelling to date (input parameters refinements, etc), compiled literature review and VP surveys to investigate gull avoidance rates to better inform the CRM and the approach to PVA. The key points raised by consultees were:
There is, and could be in the future, considerable inter-annual variation in breeding success at Alde-Ore that will need to be accounted for by the CRM and PVA; and
Potential management measures that could be undertaken to improve gull breeding success (key action: The NT agreed to scope out outline habitat management costs for 25 years)
The consultees preferred hierarchy was (i) design the wind farm to minimise the level of collision, (ii) reduce the level of fishing activity (thereby reducing the level of flight activity within the wind farm), and (iii) continue supporting habitat management on the SPA over the lifetime of the wind farm, to increase the population.
13th The JNCC Rafe Dewar (RPS) had a telephone meeting with Sophy Allen (the JNCC) to discuss the Section 11.7 and Annex 4 of October RPS Technical Report (submitted to SNCAs on 9th September 2011) and information to Technical Appendix 11.A. 2011 inform Appropriate Assessment prior to comments on draft and submission of final
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Date Consultee Summary of issue Section where addressed version. Key items raised by the JNCC included:
The JNCC and NE do not consider that the current PVA is sufficiently in-depth to provide sufficient evidence to show beyond reasonable scientific doubt that a significant impact on LBBG would be avoided. Key action: An agreement will be required on the input parameters on demographic rates. SA concurs with RD that an agreement could be made without the requirement of future surveys of the SPA population. It was recommended that at least one meeting should take place to reach agreement with the SNCAs and the RSPB on the PVA input parameters.
14th The JNCC and Comments received from the JNCC and NE on the RPS Technical Report submitted to Section 11.7, Annex 4 of October NE the SNCAs on 9th September 2011. Feedback focused on the ongoing refinements to Technical Appendix 11.A 2011 the CRM and the demographic rates/interpretation presented for the PVA. and Section 7 (Information to Inform AA) in the HRA Report.
21st The RSPB Comments received from the RSPB on the RPS Technical Report submitted to them on Section 11.7, Annex 4 of October 9th September 2011. Similar to the SNCAs, advice and clarifications were largely Technical Appendix 11.A 2011 focussed on the CRM and PVA. Section 7 (Information to Inform AA) in the HRA Report.
21st London Array A meeting with Keith Henson, the Principle Ornithological Advisor at London Array Section 11.10 October Limited Limited, confirmed that the LA density estimates, CRM outputs or red-throated diver 2011 habitat association modelling assessment (Skov, In Prep) would not be publicly available
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Date Consultee Summary of issue Section where addressed until November 2011.
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11.3 Methodology
The study area 11.3.1 The relative abundance, seasonal distribution and behaviour of avifauna known to occur within or adjacent to the GWF site and export cable corridor will be considered in the context of regional dynamics across the Outer Thames Estuary and southern North Sea.
11.3.2 The GWF study area comprises the extent of the outermost possible development site boundaries, plus a buffer of up to 4km, Figure 11.2, and is therefore smaller in extent than the boat-based and aerial survey areas.
11.3.3 There are two distinct application boundaries, which represent extensions to the GGOWF: to the north is Area A, and to the south are Area B and Area C, Figure 11.1.
11.3.4 In general, population estimates and impacts have been combined for adjoining Areas B and C due to the relatively small extent and sample sizes of Area C. Further details of the treatment of these reporting regions can be found in Section 1b, Technical Appendix 11.A.
11.3.5 As the GGOWF is adjacent to the GWF, there are areas of the GWF and its buffers that overlap with the footprint and buffers of the GGOWF, leaving only partial non-overlapping buffer areas, Figure 5 of Technical Appendix 11.A. Further detail of the temporal-spatial nature of construction activities at GGOWF can be found in Section 11.3.13 below.
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Characterisation of the existing environment
11.3.6 In order to provide spatial and temporal information on avifauna within the proposed development area and regional waters, several sources have been used to inform the site characterisation within this ES.
11.3.7 The following boat-based survey data have been used to inform the impact assessment:
2004-06 surveys conducted to inform the EIA for the Greater Gabbard Offshore Wind Farm (GGOWF); June 2008 to May 2009 pre-construction surveys as part of the GGOWF monitoring requirements, which extended the survey area to cover the GWF site; and June 2009 to May 2010 surveys, which covered the GGOWF and GWF sites, with construction activity commencing in the former site in August 2009.
11.3.8 The following aerial survey data have been used to inform the assessment:
2004/05 aerial surveys of the Thames Strategic Area (TH1-TH5 sectors) (DTI, 2006); 2005/06 aerial surveys of the Thames Strategic Area (TH1-TH7 sectors) (BERR, 2007); 2007/08 aerial surveys of part of the Thames Strategic Area (TH1) and Greater Gabbard area (GG1-4) (DECC, 2009); and 2009 surveys of Round 3, Zone 5 (NS1-NS3) WWT Consulting (2009).
11.3.9 The temporal and spatial coverage of all surveys which have been used to inform the impact assessment presented in this Chapter is provided in Table 11.3.
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Table 11.3 Data sources to inform site characterisation of the offshore ornithological assemblage at the GWF
Year Nature of the data Spatial coverage Month
J F M A M J J A S O N D
2004 Boat-based surveys GGOWF N/S
2005 Boat-based surveys GGOWF N/S N/S I/S N/S N/S
2006 Boat-based surveys GGOWF I/S I/S
2008 Boat-based surveys GGOWF and GWF N/S I/S
2009 Boat-based surveys GGOWF and GWF N/S I/S
2010 Boat-based surveys GGOWF and GWF I/S I/S
2004 Aerial Survey TH3 (covers GWF footprint)
2005 Aerial Survey TH3 (covers GWF footprint)
2006 Aerial Survey TH3 (covers GWF footprint)
2008 Aerial Survey GG1-4 (covers GWF footprint)
2009 Aerial Survey NS1-7 (R3, Zone 5)
Source: RPS (September 2011), Technical Appendix 11.A. Key: I/S = incomplete survey; N/S = no survey due to poor conditions. Yellow shading denotes regional surveys (variable coverage of the GWF footprint and its associated buffers), shades of pale blue denote site-specific surveys at the GWF before commencement of construction at the GGOWF, darker blue shading denotes site-specific surveys completed whilst construction at the GGOWF was ongoing.
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Boat-based surveys 2004-2010 11.3.10 Boat-based surveys were undertaken between 2004 and 2010 by Ecological Consulting (February and March 2004 only), the British Trust for Ornithology (BTO) and Environmentally Sustainable Systems Limited (ESS Ecology), Table 11.3. Boat-based bird surveys aimed to establish the numbers, distributions, seasonal and inter-annual patterns, flight heights and directions of birds found to be present within the study area as well as to create a repeatable baseline for future monitoring requirements.
11.3.11 The monitoring protocol included a programme of monthly boat-based transect surveys Figure 11.2, following the standard methodology as recommended by Camphuysen et al., (2004).
11.3.12 For further details on the sampling protocol, data processing and analytical approach for these boat-based surveys, refer to Section 2b of Technical Appendix 11.A.
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GGOWF construction programme 11.3.13 Figure 11.3 shows that monopile installation at GGOWF commenced in August 2009 (Quarter 1). A single monopile was installed during this month, within the eastern extent of the Inner Gabbard site. During Quarter 2 (September to November 2009), construction at the site comprised of the installation of a total of 31 monopiles within the eastern extent of the Inner Gabbard site, four of which were installed during days when the ornithological surveys were underway. Construction involved the use of a number of construction vessels throughout the quarter, including a crane vessel, anchor handling tug and a diving support vessel.
11.3.14 Construction was ongoing at GGOWF whilst bird surveys were underway during Quarter 3 (December 2009 to February 2010). A total of 35 monopiles were installed within the eastern and south eastern extent of the Inner Gabbard site during the quarter. Two monopiles were installed during days when the ornithological surveys were underway (installed in December). During the January and February surveys, construction activity included the installation of six J-tubes and two transition pieces within the eastern extent of the Inner Gabbard. Pre-cable lay mattress protection was also installed during the January survey.
11.3.15 Construction was ongoing at GGOWF whilst bird surveys were underway during Quarter 4 (March to May 2010). Construction activity included the installation of 45 transition pieces and four wind turbine generators (WTGs) within the eastern extent of the Inner Gabbard, Table 3, Technical Appendix 11A.
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The impact of GGOWF construction activities on concurrent boat-based ornithological surveys at GWF 11.3.16 From consultation with the JNCC and Natural England, Table 11.2, it was determined that if possible, at least two years of data (2008-2009 and 2009- 2010) should be used to inform the EIA. This is to increase the reliability of data analysis by recording natural inter-annual variation of numbers and distributions of species. Boat-based survey data that are included were collected from June 2008 to May 2010.
11.3.17 In the case of the GWF ornithological baseline, the two years of approximately-monthly boat-based seabird surveys have overlapped with the commencement of the construction of the adjacent GGOWF, in August 2009. Due to the proximity of the GGOWF site and, therefore, construction activities, it was acknowledged during consultations with the JNCC and Natural England, Table 11.2, that there are statistical complexities associated with data analysis of the GWF alone, or cumulatively with GGOWF, due to the potential influence of such activities on population distribution and numbers in the GWF study area. As a result, it was necessary to determine if there is any evidence that disturbance due to the construction activities has had a detectable, and significant, effect on the seabird abundances recorded during the second year of the boat-based surveys.
11.3.18 Although June 2008 to June 2009 surveys were considered to represent the ‘pre-construction’ year and June 2009 to June 2010 the ‘construction’ year, in practice construction activity only commenced in August 2009, after that month’s survey, Table 11.4. By the end of September 2009, only one monopile was installed within the whole GGOWF, and the second was installed during the first boat survey day in September. This installation took place in the Inner Gabbard turbine area, some 11km from the closest point of boat surveying, which occurred in the south-west portion of the GWF survey area, beyond the Inner Gabbard turbine area. No observation notes were made during that day’s survey that related to pile-driving activity or associated bird behaviour. It should also be noted that construction activity did not take place on the subsequent survey days that month, Table 11.4.
11.3.19 It can, therefore, be reasonably concluded that numbers of seabirds within the main 2009 breeding season (and main migratory peak for skuas) in the GWF survey area were not significantly affected by disturbance-displacement due to construction activities. Therefore, relative monthly populations in June to September 2008 and 2009 can be directly compared without question of construction activity having an influence on bird numbers or distribution.
Statistical methods used to compare inter-annual variation 11.3.20 Extensive consultation with the JNCC, Natural England and the RSPB was undertaken in order to reach agreement on the use of the two year dataset to inform the baseline, and the extent to which it can be demonstrated that there is any evidence of a systematic reduction due to construction activities in
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particular months.
11.3.21 A series of statistical methods were employed by RPS to investigate any evidence of inter-annual variation – (i) a Generalised Linear Mixed Model (GLMM); (ii) a kernel density analysis, and; (iii) a Jacobs’ Selectivity Index (JSI). Further details of the methods, analysis and interpretation of this statistical work can be found in Section 2f of Technical Appendix 11.A.
11.3.22 After consultation with the JNCC and Natural England, where the outcomes of the three tests were presented, it was agreed that, based on the limitations of interpreting the complex dataset, it was not possible to demonstrate for certain that any inter-annual differences in populations are due to construction activities, or simply part of a natural variation. Further details of this consultation can be found in Section 2.74 of Technical Appendix 11.A.
11.3.23 Given the nature of much of the seabird data, dominated by large ephemeral gull flocks which are likely to skew the data, and ‘noisy’ background variation which is almost impossible to disentangle from GGOWF effects, RPS asserted that even more sophisticated modelling (such as Density Surface Modelling, as advocated by the JNCC and NE) is likely to yield the similar inconclusive results.
11.3.24 It was therefore agreed that for any months where construction activity was concurrent with boat-based surveys, the worst-case monthly population estimate from either of the survey years will be used for the impact assessment (meeting with the SNCAs, 15 April 2011). Where it can be justified that there were no construction impacts (i.e. construction activities did not occur on survey days), an average of the two years will be presented. The range of population size between the two years will also be presented (in parentheses). Population estimates for the following months therefore use worst-case estimates, i.e. the highest value of either year: October, December, March, April and May. All other months will use an average of the two years.
Aerial surveys 11.3.25 Aerial surveys conducted for the Thames Strategic Area, and for the GGOWF area were undertaken during winter months between 2004 and 2009. Three surveys have taken place which covers at least part of the GWF site (DTI, 2006; BERR, 2007; DECC, 2009), which falls within survey block TH3, or GG1-4 in the case of DECC, 2009, Figure 11.4. In addition, surveys by WWT (2009) covered the Round 3 Zone 5 areas to the north of GWF in spring 2009. The methodology used for these surveys was developed in Denmark by the National Environment Research Institute (NERI) (Kahlert et al 2000; Camphuysen et al 2004).
11.3.26 For further details on the sampling protocol, data processing and analytical approach for these aerial surveys, refer to Section 2c of Technical Appendix 11.A.
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GGOWF Vantage Point Surveys 11.3.27 In June 2011, the opportunity arose for GWFL to ground-truth CRM calculations for gulls from an additional programme of observational vantage point (VP) surveys within an operational section of the GGOWF. An approach was designed to monitor actual flight activity for lesser black- backed gull in particular, within and in proximity to the air volumes swept by the operational turbines. Full details of the methods and results of these surveys are presented in Annex 4 of Technical Appendix 11.A.
11.3.28 VP watches are a means of quantifying flight activity of bird species that take place within and in proximity to the rotor swept area of a wind farm, with the principal aim of determining the likely collision risk after turbines have become operational. The series of field observations in June and July 2011 had the following objectives:
Confirm (to the extent possible) the actual rate of lesser black- backed gull collisions within an operational wind farm; Quantify and characterise the flight activity of lesser black- backed gulls within the rotor swept area of an operational wind farm; and Describe any apparent avoidance and near-blade evasive behaviours to provide qualitative information to inform the choice of gull near-blade “micro” avoidance rate (manifest as evasive flight manoeuvres), and extent of macro-avoidance (which will of necessity reduce rotor passage and collision rates), and to inform the EIA. 11.3.29 During each watch, the 180 degree arc area in view was scanned until a target species is detected: at which point it is followed until it ceases flying, is lost from view, or reaches a distance of over 2km from the observer. Section 1.10 of Annex 4, Technical Appendix 11.A provides details of the type of movement and flight behaviour data that was recorded by this monitoring.
11.3.30 Although lesser black-backed gull was the primary target species for this monitoring, if none were seen then secondary focal species were selected (if visible) from the hierarchy of: other large gull species; great black-backed gull; and herring gull. It should be noted that there were no periods of higher gull activity, when recording over a 180 degree viewshed may have become overwhelming, and so all individuals of target species were recorded during each survey period.
Desk based assessment of regional information 11.3.31 Background information on seabird distribution within the North Sea was taken from Stone et al., (1995) and Mitchell et al., (2004), the latter included colony counts during the JNCC’s Seabird 2000 survey programme. These were used to determine regional breeding numbers and distribution for each species. Seabird colony count datasets up to October 2010 were obtained
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from the JNCC (JNCC, 2011). Much of the information on bird behaviour and ecology has been taken from Birds of the Western Palaearctic interactive version (Cramp and Simmons, 2004), which provides a comprehensive text on each species, and is the commonly used standard reference text in the industry.
11.3.32 Further information on seabirds in the Outer Thames Estuary is taken from surveys conducted for ES’s and monitoring reports of the London Array (RPS 2005, Gunfleet Sands II (DONG Energy, 2007), Thanet (TOW, 2005) and Kentish Flats (Gill et al., 2004) offshore wind farm developments.
Data analysis Population estimates 11.3.33 The site characterisation presented in this Chapter is informed by technical analysis undertaken by RPS (September, 2011), Technical Appendix 11.A.
11.3.34 Raw data collected by boat-based and aerial surveys for GWF and GGOWF were corrected to account for the area sampled relative to the study area, as recommended by Maclean et al. (2009). Distance software was used to account for undetected birds (Buckland et al. 2001; Thomas et al. 2010) for species with sufficient observations, Section 2f Technical Appendix 11.A.
Collision Risk Modelling 11.3.35 To quantify the potential risk of additional mortality above the current baseline for each species caused by collisions with operational turbines, CRM has been undertaken, generally following recommendations in the guidance by MacLean et al. (2009). In this, the authors recommend that a version of the Band et al. (2007) model is used, which has been the standard method for most onshore and more recent offshore wind farms to date.
11.3.36 Consultations were undertaken with the JNCC and Natural England on the approach and refinements to the CRM, to establish whether (i) the version of the Band model used here was suitable and sufficient for estimating mortality rates for species of principal concern; and (ii) how species should be selected, or omitted from modelling. Subsequent to the discussions during the meetings detailed in Table 11.2, these resolutions were captured in a Collision Risk Modelling Note (RPS, dated 29 June 2011) which was submitted to the SNCAs.
11.3.37 Further details of the outcomes of this consultation and the input parameters taken forward as part of the CRM are detailed in Section 2.76- Section 2.98 of Technical Appendix 11.A.
Assessment of impacts 11.3.38 The details provided in Chapter 5 Project Details have been used to establish a realistic worst case development scenario as established in the principles of the Rochdale Envelope. This chapter assesses the potential impacts of the offshore assets of the GWF (namely the wind farm array and
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offshore export cable). Section 11.5 provides detail on the worst case assumptions that have been used to inform the assessment of impacts within this ES.
11.3.39 Assessment of the significance of potential impacts on ornithological interests uses a matrix-based approach based on guidance by Maclean et al. (2009), whereby the sensitivity of each species to an impact, and the corresponding magnitude of impact are cross-tabulated to quantitatively assess the significance of impacts, as a means of backing-up “expert judgement”. Matrices have been commonly employed in Round 2 wind farm EIAs, although it is acknowledged that during consultation, JNCC and Natural England warned against over-reliance on these as tools.
11.3.40 To account for this, the methodology therefore also considers key complimentary components of IEEM’s (2010) Ecological Impact Assessment Guidelines for Marine and Coastal Projects, which is endorsed by Maclean et al. (2009), and is generally supported by JNCC and Natural England.
11.3.41 Within the IEEM (2010) guidance, predicting and characterising impacts on species (e.g. extent, duration, magnitude and confidence in predictions) within various geographical contexts (e.g. national or regional populations) or designated sites is carried out on the basis of species distribution and status, and this procedure is followed here.
11.3.42 As mentioned, to avoid over-reliance on the matrix approach, expert judgement is a concept which IEEM (2010) suggests should be used to assess the likelihood of a significant impact occurring. The results of the matrix approach are therefore overridden by expert judgement where there is a clear and justifiable reason for doing so.
11.3.43 A key component of the impact assessment process is determining whether impacts are ecologically significant. An ecologically-significant impact is defined by IEEM (2010) guidelines as “an impact that has a negative, or positive, effect on the integrity of a site or ecosystem and/or the conservation objectives for habitats or species populations within a given geographical area. In this way significant impacts are distinguished from other, lesser (and, in the context of EIA, unimportant) effects.”
11.3.44 The impact assessment therefore aims to determine for each identified impact, whether there is a potential for it to significantly affect the integrity of a population, site, ecosystem and/or the conservation objectives of an SPA. As it is impossible to investigate all issues in detail, analysis concentrates on those issues most likely to generate significant ecological impacts (negative or positive). This is consistent with the EIA Regulations1, which only require identification of likely significant effects. The potential impacts associated
1 The UK statutory instruments that are designed to meet the requirements of Council Directive 85/337/EEC on the Assessment of the effects of certain public and private projects on the environment, as amended by Council Directive 97/11/EC.
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with offshore wind farms and birds are outlined in Section 11.7.
11.3.45 The elements used to define the nature of the impact include determining:
The positive or negative nature of effects; The potential duration, whether short-term (construction or decommissioning phase) or long-term (operational phase or longer); Whether effects are permanent or reversible; The spatial extent / magnitude of the effect; Whether the effect is direct or indirect; and Whether there are any cumulative effects that may affect the long- term integrity of the ecosystem(s) at the site.
11.3.46 Where no conservation designations apply, significance can be evaluated by using the proportional extent of a population, and by identifying the geographical scale at which the impact is significant. Criteria for establishing significance when considering designated sites (SPAs) is however different, as the process of site selection and a site’s Conservation Objectives must be taken into account (IEEM, 2010). These differences for determining significance, and how they are reflected by the impact assessment approach are expanded on later in this section.
11.3.47 In general, the potential significance of effects are determined through understanding how each species is affected by the development. This takes into consideration the following:
Population estimates of each species within the GWF and surrounding area; The magnitude of the effect, based on the extent and duration of each effect on a particular population, and the proportion of which may be affected within a specific geographical context; The population status of each species at a national, regional or site level; The distribution of populations for each species within the study area; The sensitivity of each species to particular impacts; The ecology and behaviour of each species (e.g. flight and feeding characteristics); and The resultant level of importance of the site to each species, based on the above factors.
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11.3.48 To determine the significance of an impact, a sequence of criteria are evaluated against each species and each impact:
Receptor sensitivity: based on a combination of the conservation value of the species and the vulnerability of the species to each particular impact; Magnitude of impact; Significance: based on a combination of (1) and (2) above to determine which effects on which species may be considered significant in terms of the EIA Regulations; and The likelihood of such an event occurring: based on expert judgement.
11.3.49 These four steps are described in sequence in the following sections.
Receptor Sensitivity 11.3.50 Evaluation of the ornithological assemblage identified by the baseline studies has been assessed in relation to its conservation status over a full range of geographical scales as listed in Table 11.5. This has been used to determine each species sensitivity in a regional, national or international context.
Table 11.5 Definition of terms relating to the sensitivity of ornithological receptors
Value Examples
International Bird species that form part of a cited interest of an SPA, SSSI or Ramsar site that may potentially interact with the study area at some stage of their life cycle.
A bird species for which a significant proportion (more than 1%) of the international population is found within the site
National Bird species that form part of an assemblage qualification of an SPA or SSSI that may potentially interact with the study area at some stage of their life cycle.
A bird species for which a significant proportion (more than 1%) of the national population is found within the site
An impact on an ecologically-sensitive species (<300 breeding pairs in the UK)
Regional Bird species that are listed on Annex I of the EU Birds Directive or on Schedule 1 of the Wildlife and Countryside Act 1981, requiring increased legal protection from disturbance during the breeding
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Value Examples season
A species listed on the Birds of Conservation Concern Red list
Birds that are the subject of a specific action plan within the UK Biodiversity Action Plan.
A bird species for which a significant proportion (more than 1%) of the regional population is found within the site, or at the extremity of a distributional range.
Local Any other species of conservation interest (e.g. Amber-listed species listed on the Birds of Conservation Concern not covered above).
Negligible All other species of low Conservation Concern
11.3.51 For each impact (e.g. habitat loss, disturbance, collision risk), general species sensitivity is assessed by taking into consideration how vulnerable species are to that impact, e.g. how flexible the species is in its habitat use or susceptibility to disturbance, based on classification by Garthe and Hüppop (2004), Table A.4, Annex 1 of Technical Appendix 11.A, interpretation by Maclean et al. (2009), as well as recent findings from operational wind farms, e.g. Krijgsveld et al. (2010), Petersen et al. (2006), Cook et al. (in prep.).
11.3.52 Each species of principal concern’s potential sensitivity to a specific impact is shown in Table 11.6. This resultant general species sensitivity can be assessed against conservation value (from Table 11.5) and shown in Table 11.7 below (from Maclean et al. 2009). For example, although lesser black- backed gulls are of ‘Low’ sensitivity to disturbance, as an SPA-qualifying species their conservation status is ‘International’, resulting in an overall ‘Medium’ sensitivity of the populations found in the GWF survey area to disturbance.
Table 11.6 General Species Sensitivity of ornithological receptors in relation to specific impacts
General Species Sensitivity to Specific Impacts
Species Disturbance1 Habitat Loss Collision Risk3 Barrier / Indirect Effects4 Disturbance2
Red-throated Very high High Medium High diver
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General Species Sensitivity to Specific Impacts
Species Disturbance1 Habitat Loss Collision Risk3 Barrier / Indirect Effects4 Disturbance2
Fulmar Very low Very low Low Low
Gannet Low Very low Low Very low
Arctic skua Very low Very low Low Low
Great skua Very low Very Low Low Low
Common gull Low Low Medium Very Low
Lesser black- Low Low Medium Very Low backed gull
Herring gull Low Low Medium Very Low
Great black- Low Low Medium Very Low backed gull
Kittiwake Low Low Medium Very Low
Guillemot Medium Medium Low High
Razorbill Medium Medium Low High
1: based on disturbance by ship and helicopter traffic by Garthe and Huppop (2004) and Maclean et al. (2009); 2: based on habitat use/flexibility by Garthe and Huppop (2004) and habitat loss in Maclean et al. (2009); 3: based on flight manoeuvrability, flight altitude, % flying and nocturnal flight activity in Garthe and Huppop (2004), flight patterns in Krijgsveld et al. (2010) and flight heights in Cook et al. (in prep.); and 4: based on barrier effects in Maclean et al. (2009), Krijgsveld et al. (2010) and Petersen et al. (2006)
Table 11.7 Determination of overall sensitivities of ornithological features in the GWF survey area to each predicted impact (‘GWF site-specific sensitivity’)
Conservation Sensitivity to impact (e.g. habitat loss, collision risk) Value Very high High Medium Low Very low sensitivity
International Very high Very high Very high Medium Low
National Very high High High Medium Low
Regional Very high High Medium Low Low
Local High Medium Low Low Very Low
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Negligible Medium Low Low Very Low Very Low
Magnitude of Impacts 11.3.53 The magnitudes of effects on each species are defined in Table 11.8.
Table 11.8 Defining the magnitude of effect on ornithological receptors
Magnitude Description
Very High Would cause the loss of a major proportion or whole feature / population, or cause sufficient damage to a feature to immediately affect its viability. Irreversible. (>80% population loss)
High Major effects on the feature / population, which would have a sufficient effect to irreversibly alter the nature of the feature in the short-to-long term and affect its long-term viability, for example more than 20% population loss.
Medium Effects that are detectable in short and long-term, but which should not alter the long-term viability of the feature/ population, for example between 5-20% population loss.
Low Minor effects, either of sufficiently small-scale or of short duration to cause no long-term harm to the feature / population, for example 1-5% population loss.
Negligible A potential impact that is not expected to affect the feature / population in any way; therefore no effects are predicted (<1% population loss).
Significance and confidence in predictions 11.3.54 The significance of a potential effect on each species was determined by considering the magnitude and duration of the effect (Table 11.8) in relation to the overall sensitivity of the species (Table 11.7). Significance is described as Major, Moderate, Minor or Negligible, or within a range e.g. Major – Moderate as given in Table 11.9. To continue the previous example, a disturbance impact of Low magnitude on lesser black-backed gull (Medium sensitivity) would result in an impact of ‘Minor’ significance.
Table 11.9 Significance of an impact resulting from each combination of GWF site- specific sensitivity and the magnitude of the effect upon it
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Sensitivity
Impact Very High High Medium Low Magnitude
Very High Major Major Major Moderate
High Major Major Moderate Minor
Medium Major Moderate Minor Minor
Low Moderate Minor Minor Negligible
Negligible Minor Negligible Negligible Negligible
Note: shaded cells (red to yellow) indicate impacts of some or serious concern
11.3.55 The significance level generated from Table 11.9 is then assessed against the likelihood of such predictions occurring, and the confidence level of the impact on a population, based on expert judgement and literature evidence. A scale of confidence, as recommended by IPCC (2005) can then be used:
Virtually certain: >99% probability of occurrence; Very likely: >90% probability; Likely: >66% probability; About as likely as not: 33-66% probability; Unlikely: <33% probability; Very unlikely: <10% probability; and Exceptionally unlikely: <1% probability.
11.3.56 Using these criteria, and with rationale to explain the reasoning, the predicted level of significance may be altered either downwards, e.g. from Major to Moderate, or upwards, e.g. from Minor to Moderate, based on expert judgement and scientific evidence.
Non-designated populations 11.3.57 As outlined above, the significance of the impact identified on species populations that are not linked to designated sites can be defined according to the terminology in Table 11.10, and taking into account IEEM (2010) guidelines outlined above. Using these as a reference, impacts defined as being of ‘Major adverse’ or ‘Moderate adverse, but not likely to be tolerable’ have the potential to result in a significant impact, defined against the relevant geographical scale, and duration, e.g. “an impact of long-term Moderate adverse, but not likely to be tolerable significance on the population of lesser black-backed gull at a regional level”.
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11.3.58 The issue of what is a ‘tolerable’ level of impact has not been specifically defined in EIA guidelines, although it is generally accepted that populations or habitats will have a threshold for absorbing deterioration and a certain capacity for recovery. Therefore to be tolerable, it should be demonstrated that any losses should be within the regenerative capacity of the reference population or habitat to be absorbed, and result in the population or habitat extent remaining viable over the long-term.
11.3.59 Impacts that are Moderate adverse but tolerable, Minor adverse or Negligible are not considered to be significant against a particular geographic scale (e.g. national), although it should be noted that they may be so at a lower scale (e.g. regional).
Table 11.10 Terminology for classifying environmental impact
Impact Significance Definition
No impact There is an absence of one or more of the following: impact, source, pathway or receptor.
Negligible The impact is not of concern.
Minor adverse The impact is undesirable but of limited concern
Moderate adverse The impact gives rise to some concern but is likely to be tolerable (depending on the scale and duration).
Major adverse The impact gives rise to serious concern; it should be considered as unacceptable.
Minor beneficial The impact is of minor significance but has some environmental benefit.
Moderate beneficial The impact provides some gain to the environment.
Major beneficial The impact provides a significant positive gain.
Natura 2000 site significance 11.3.60 The JNCC and Natural England commented in the Section 42 consultation response letter (July 2011) that whilst the descriptors of magnitude are helpful, the specific figures relating to population loss listed in Table 11.8 are not Natura 20002 compliant, and advise against using these figures too literally in such cases. For example, what may otherwise be considered a ‘Low’ magnitude impact (1-5% of population loss) may still result in an adverse impact on the integrity of an SPA, if the extent of habitat or population affected is particularly vulnerable. Based on Natura 2000
2 Natura 2000 sites are either a Special Protection Area (SPA), classified under the EC Birds Directive (2009/147/EC, the codified version - updated to incorporate the original act and all amendments of Council Directive (79/409/EEC), or a Special Area of Conservation (SAC), designated under the Habitats Directive.
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guidelines (e.g. EU, 2010), and unlike the EIA process, there are no degrees of significance – either there is an adverse effect on the SPA or there is not. In this assessment, impact magnitudes and resultant significance will therefore be considered specifically within the context of relevant SPA populations, where appropriate. Commonly this is based on whether the site’s Conservation Objectives are compromised by any aspect of the development.
11.3.61 Conservation Objectives are required for all of these Natura 2000 sites and the overriding aim is the maintenance, or where appropriate, the restoration of the ‘favourable conservation status'’3 of species and habitat features for which SPAs (and SACs) are designated.
11.3.62 In the broadest terms, 'favourable conservation status' means a feature is in satisfactory condition and all aspects and processes needed to maintain it for the foreseeable future are in place. Favourable conservation status of a species is defined in Articles 1(e) and 1(i) of the Habitats Directive as: “The conservation status of a species is the sum of the influences acting on the species that may affect the long-term distribution and abundance of its populations. The conservation status will be taken as ‘favourable’ when:
Population dynamics data on the species indicate that it is maintaining itself on a long-term basis as a viable component of its natural habitats; The natural range of the species is neither being reduced nor is likely to be reduced for the foreseeable future, and There is, and will probably continue to be, a sufficiently large habitat to maintain its populations on a long-term basis.”
11.3.63 For the purposes of this assessment, instead of Table 11.9 and Table 11.10 being considered for assessment of SPA-level effects, in most cases, a significant effect on the Conservation Objectives (maintenance or restoration of favourable conservation status) and therefore the integrity of an SPA will not occur if it can be shown that in the long-term, the population of the species as a viable component of the site will clearly be maintained, despite predicted impacts.
Mitigation and residual impact 11.3.64 In the cases where a significant adverse impact is identified, mitigation measures (i.e. means by which impacts might be avoided, reduced or managed) may be required to render likely impacts non-significant, either as part of the design or as a measure implemented during the construction, operation or decommissioning phases. Those considered Moderate will be subject to expert judgement as to whether mitigation is required (i.e. whether
3 The concept of Favourable Conservation Status is not mentioned in the Birds Directive but there are analogous requirements, i.e. all SPAs must still be subject to special habitat conservation measures in order to ensure the survival and reproduction of the Annex I birds in their area of distribution.
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they are already ‘Moderate but tolerable’ or not). Those impacts defined as ‘Minor adverse’, ‘Negligible’ or ‘No impact’ do not require mitigation measures and are not considered significant by the EIA Regulations, although mitigation may often be described for these as they further reduce the magnitude of any predicted effects.
11.3.65 The significance criteria listed in Table 11.10 are used to predict the residual significance of each potential effect following mitigation and enhancement.
Monitoring 11.3.66 Monitoring will be required where it is conditioned in the Marine Licence. The purpose and objectives of monitoring Round 2.5 projects will need full consideration and consultation with relevant stakeholders prior to implementation. This is discussed in more detail within Section 11.11.
Scope of species to be included in the EIA 11.3.67 A total of 76 species (including birds identified to genus or family level only) have been recorded on boat-based surveys during 2008/09 and 2009/10. Many of these species have, however, been recorded in very low numbers within the context of regional, national or migratory flyway populations, and/or are of low conservation value. It is, therefore, unnecessary to include these species in an assessment, as even in a worst-case scenario, total numbers affected will not approach a 1% significance level at regional, national or international scale, which is normally considered an appropriate threshold for impact assessments. Species found at GWF within foraging ranges of SPA populations where they are a qualifier have been considered as part of an assessment of Natura 2000 sites and species.
11.3.68 Initial selection criteria of the species identified by the baseline studies have been informed by IEEM’s (2010) guidance, and from various consultations with the JNCC and Natural England, to ensure that full transparency has been shown in the compilation of the species of principal concern list.
11.3.69 The species to be considered are those of concern due to being rare or vulnerable to potential impacts, or where it is shown that the UK is important to the species. This will include at least one of the following criteria:
a qualifying species of a nearby SPA, SSSI or Ramsar site; appearing on Annex I of the Birds Directive and/or on Schedule 1 to the Wildlife and Countryside Act; a regularly-occurring migratory species; the UK supports an internationally-important population of the species; the species is on the Red-Listed Birds of Conservation Concern (Eaton et al. 2009); and/or there is a population within the GWF study area deemed sufficiently large as to be of international or national importance.
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11.3.70 All other species are excluded from the selection procedure. A full list of species, with associated conservation value, showing all records of birds on the sea and in flight during GWF boat-based surveys in 2008/09 and 2009/10 is shown in Table A.6 in Annex 1 of Technical Appendix 11.A.
11.3.71 It was considered that all species with 5 or fewer counts (both in and out of transect) between June 2008-May 2010 combined, were not present in sufficient numbers to be included, regardless of conservation status, and indeed an accurate assessment would not likely be possible, due to the small sample size. It follows that these excluded species would not be affected in numbers that nearly reach significance at a SPA, regional or national level, under the terms of the EIA Regulations.
Migratory species 11.3.72 Passage migrants, which include seabirds, waders, waterfowl and passerines, may pass through the GWF site once or twice a year, as they travel to and from breeding and wintering grounds. These species may only be recorded in small, insignificant numbers by boat and aerial surveys, which sample only a small part of the migratory period. However, it is acknowledged that their cumulative numbers passing through the site throughout this period may be much larger and constitute an important part of a population, for example of an SPA.
11.3.73 Nevertheless, none of the migratory species omitted from Table 11.11 are considered likely to be at risk from any aspect of the GWF development. Other identified migratory species were Arctic tern Sterna arctica, black- throated diver Gavia immer, Manx shearwater Puffinus puffinus, Pomarine skua Stercorarius pomarinus and Cory’s shearwater Calonectris diomedea (maximum of three records per annum), and Balearic shearwater Puffinus mauretanicus (one record). The impacts on migratory species are likely to be limited to collision risk and barrier effects, with displacement and disturbance likely to be unimportant due to their brief site usage. Only Balearic shearwater had a single flight within snapshot, and since zero flights for each of these species were at rotor height, it follows that none of the above species are likely to be at risk from collision mortality, nor due to the wide- ranging migration patterns of all these species, will barrier effects be likely.
Final scope of species of principle concern 11.3.74 Population estimates for those remaining species of conservation concern found in sufficient numbers to be potentially included in the impact assessment are shown in Table 11.12. Estimates are for the entire survey area and are, therefore, likely to be higher than for the GWF footprint alone.
11.3.75 For further detail on the data sources used to inform the final assessment, refer to Section 3b of Technical Appendix 11.A.
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Table 11.12 Key species population estimates and importance within a national and regional context
Estimated Peak Population in Peak Population Relevant populations 2004-06 transect (boat (aerial surveys) 1% GB and month of peak surveys) and month of and period of Threshold
count peak count peak count Regional Regional Aerial Summer National breeding winter Regional Species Boat (TH3) 2008/09 2009/10 2007-08 (GG1-4) Winter Importance pairs individuals Importance
2,399 26 3,144 2,238 26 2,202 Lesser black-backed gull YES 3,520 28,788 YES Dec-05 Nov-Dec Jun-08 Jul-09 Feb 500
2,851 18,141 YES (wider 1,771 7,204 1,664 13,224 Guillemot (all auks) (all auks) TH3 area 0 29,291 YES only) Dec-05 Nov-Dec Feb-09 Apr-10 Feb 13,224
888 376 2,617 1,601 1,186 9,975 Fulmar NO 1,984 4,051 YES Oct-05 Nov-Dec Jan-09 Sep-09 Mar 9,975
1,464 1,218 2,706 1,098 2,037 7,337 Kittiwake NO 369 30,467 YES Jan-06 Jan-Feb Jan-09 Dec-10 Mar 7,337
245 139 1,311 720 1,310 4,371 Gannet NO 7,859 3,996 YES Dec-05 Oct-Nov Nov-08 Oct-09 Mar 4,371
1,714 335 1,083 383 22 2,772 Herring gull NO 1,181 64,172 YES Dec-05 Oct-Nov Jan-09 Dec-09 Feb 4,500
Razorbill 1,411 2,851 2,187 587 18,141 1,645 YES 0 6,161 YES
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Estimated Peak Population in Peak Population Relevant populations 2004-06 transect (boat (aerial surveys) 1% GB and month of peak surveys) and month of and period of Threshold
count peak count peak count Regional Regional Aerial Summer National breeding winter Regional Species Boat (TH3) 2008/09 2009/10 2007-08 (GG1-4) Winter Importance pairs individuals Importance
(all auks) (auks)
Nov-04 Nov-Dec Feb-09 Apr-10 Feb ?
572 1,450 1,306 325 19 342 Great black-backed gull YES 4 25,117 YES Dec-05 Nov-Dec Jan-09 Feb-10 Feb 400
35 94 168 318 2 964 Common gull NO 0 20,527 YES Jan-06 Feb-Mar Jan-09 Feb-10 Feb-Mar 9,000
120 729 204 71 253 50 Red-throated diver YES 0 7,998 YES Jan 06 Feb-Mar Feb-09 Mar-10 Mar 170
253 1 313 48 3 193 Great skua YES 0 539 YES Oct-05 Oct-Feb Sep-08 Sep-09 Feb 193
24 10 10* 5* 0 50 Common scoter NO 0 40,028 NO Mar-05 Oct-Nov Nov-08 Jul-09 - 500
4 0 27* 1* 0 50
Arctic skua Sep-05 NO 0 ? ? - Aug-08 Apr-09 - 50 & 06
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Estimated Peak Population in Peak Population Relevant populations 2004-06 transect (boat (aerial surveys) 1% GB and month of peak surveys) and month of and period of Threshold
count peak count peak count Regional Regional Aerial Summer National breeding winter Regional Species Boat (TH3) 2008/09 2009/10 2007-08 (GG1-4) Winter Importance pairs individuals Importance
5 27 1* 1* 0 ?
Little gull Nov, Jan, Sep, Oct- NO 0 5,626 NO Sep-04 Oct-Nov - ? Apr 09
23 2 10 8 1 2,558 Black-headed gull NO 0 6,460 NO Jul-04 Jan-Feb Jul-08 Feb-09 Feb 19,000
19 0 15* 15* 0 211 Sandwich tern NO 7 3,970 NO Apr-04 - May-09 May-10 - ?
21 0 4 11 0 n/a 50,364 Dark-bellied brent goose (combined (includes all brent NO 0 NO Sep-04 - Nov-08 Oct-09 - ? SPA observations) populations)
7 0 23* 29* 0 203 Common tern NO 64 9,540 NO Aug-04 - Aug-08 Aug-09 - ?
1 0 1 0 0 5,400 Skylark NO ? ? NO Sep/Feb - Jan-09 - - ?
Meadow pipit 12 0 0 0 0 32,000 NO ? ? NO
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Estimated Peak Population in Peak Population Relevant populations 2004-06 transect (boat (aerial surveys) 1% GB and month of peak surveys) and month of and period of Threshold
count peak count peak count Regional Regional Aerial Summer National breeding winter Regional Species Boat (TH3) 2008/09 2009/10 2007-08 (GG1-4) Winter Importance pairs individuals Importance
Sep-04 - - - - ?
26 0 236 405 0 14,740 Starling NO ? ? NO ? - Nov (1)-08 Oct-09 - ?
0 0 0 0 0 n/a Pink-footed goose NO 0 86,596 NO - - - - - 3,600
0 0 4 0 0 183 Dunlin NO 0 2,532 NO - - Nov (2)- 08 - - 5,600
7 0 1 0 0 50
Wigeon Jan (2) - NO 0 6,884 NO Oct-05 - - - 4,060 08
0 0 9 5 0 n/a Black tern NO 0 ? NO - - Sep-08 Aug-09 - ?
3 1 1 2 0 168 Cormorant NO 0 244 NO Mar-05 Jan-Feb Aug-08 Sep-09 - 230
Teal 0 0 0 0 0 30 NO ? 3,597 NO
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Estimated Peak Population in Peak Population Relevant populations 2004-06 transect (boat (aerial surveys) 1% GB and month of peak surveys) and month of and period of Threshold
count peak count peak count Regional Regional Aerial Summer National breeding winter Regional Species Boat (TH3) 2008/09 2009/10 2007-08 (GG1-4) Winter Importance pairs individuals Importance
- - - - - 1,920
2 0 0 0 0 n/a Grey plover NO 0 271 NO Apr-06 - - - - 530
3 0 2 0 0 2,100 Curlew NO ? 1,132 NO Jul-04 - Jun-08 - - 1,500
0 0 4 0 0 452 Golden plover NO 0 2,129 NO - - Aug-08 - - 4,000
0 0 0 0 0 3,080 Lapwing NO ? 5,567 NO - - - - - 6,200
0 0 6 0 0 n/a Knot NO 0 176 NO - - Sep-08 - - 2,800
Source: RPS (September, 2011), Technical Appendix 11.A. Note: yellow shading donates species occurring in levels of national or regional importance, apart from Arctic skua, which is shaded because of its conservation status.* calculated using correction factors in Stone et al. (1995)
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11.3.76 It is evident that 2008/09 and 2009/10 surveys recorded five species in nationally-important numbers within the entire GWF survey area – red- throated diver, lesser black-backed gull, great black-backed gull, great skua, common guillemot and razorbill, all of which (except razorbill) were also present in nationally-important numbers in 2004-06 (Banks et al. 2006; BTO; 2006). Common guillemot was recorded in nationally-important numbers in the larger TH3 aerial survey area in 2007/08. The peak great skua population estimate for the whole GWF survey area in September 2008 was close to the 1% international threshold.
11.3.77 An additional five species are present within the entire survey area that exceeds the 1% regional thresholds in winter and/or summer – fulmar, kittiwake, gannet, herring gull and common gull.
11.3.78 Some species may be present within the wind farm area during the migratory periods only and, therefore, surveys which cover only a small period of time, may miss peak movements. It was considered, however, that only Arctic skua, Stercorarius parasiticus, was liable to be present in potentially significant numbers during its brief migration period. Since the species is of high conservation value in the UK due to its connectivity with SPA(s) in Northern Scotland and the recent significant population decline (-34% over the last 10 years, JNCC 2011) As regional wintering and flyway populations are unknown (although will likely be relatively low), it is included in the assessment section as a precautionary measure.
11.3.79 From the other species presented in Table 11.12, both Sandwich tern Sterna sandvicensis and common tern Sterna hirundo are found in low regional breeding populations and relatively low numbers for both species recorded in the GWF study area. As per Stienen et al. (2007), both Sandwich and common tern are inshore migratory species, being most abundant within 20km of the shoreline, and so the GWF will be outside of the main migratory corridor. As such it is was concluded that these two species do not require inclusion, Section 3.48-3.50 of Technical Appendix 11.A.
11.3.80 Black tern Chlidonias niger and little gull Larus minutus do not breed in Britain, and so a comparison with national or regional breeding populations are not applicable Stienen et al. (2007). Both species are likely to be found largely inshore on passage only. Compared to estimated migration numbers of little gull (30-75,000 individuals), a peak estimate of one individual in both survey years is unlikely to be important within the context of the passage population, even accounting for under-recording due to small sample periods. Again, it was concluded that these two species do not require inclusion, Section 3.51-3.52 of Technical Appendix 11.A.
11.3.81 During consultation, Table 11.2, the JNCC and Natural England recommended that, due to their high conservation value and the challenges of capturing peak numbers from snapshot boat surveys, pink-footed goose Anser brachyrhynchus and dark-bellied brent goose Branta bernicla bernicla be screened into the GWF EIA. Table 11.12 suggests that although both
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species were recorded during the spring and autumn migration periods, very few dark-bellied brent geese (including all ‘brent’ and unidentified goose records) were recorded in flight during transect and within the GWF study area, and no pink-footed geese (including unidentified geese) were recorded within the GWF study area. Only one dark-bellied brent goose was recorded in flight within the snapshot counts. Based on the regional combined SPA population estimate of 50,000 birds, any effects would be small compared to the 1,000-3,000 birds shot annually in south-east England (Ward, 2004). Although peak numbers on migration may be missed, flight height is likely to be above rotor height (Cook et al. In Prep.) and therefore birds will be at minimal risk of collision or barrier effects. It is therefore considered that pink- footed goose and dark-bellied brent goose do not warrant inclusion in the GWF impact assessment.
11.3.82 It was highlighted during consultation with the JNCC that common scoter Melanitta nigra should also be considered for inclusion in the GWF EIA. However, as suggested by Table 11.12, relatively few records were of birds observed during transect (a total of 20 birds over two years). The peak monthly count within the GWF study area was of 10 birds, which equates to 0.02% of the regional winter population. As such, common scoter have not been considered further in the GWF assessment.
11.3.83 Section 3.56 to 3.59 of Technical Appendix 11.A highlights that all other species of wader and wildfowl recorded within the GWF boat-based surveys were found in low numbers, well below levels of regional significance, Table 11.12. Evidence from the GGOWF 2004/05 ‘migration watches’ (Banks et al. 2006) supports the assumption that it is unlikely that any large numbers of migratory species have been missed during GWF surveys. It was evident that no other species to those highlighted above in Table 11.12 were recorded in high enough numbers to warrant further consideration in the GWF impact assessment.
11.3.84 Based on the information above, the assessment presented in this ES comprises 12 ‘species of principal concern’:
Arctic skua; Common guillemot; Common gull; Fulmar; Gannet; Great black-backed gull; Great skua; Herring gull; Kittiwake;
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Lesser black-backed gull; Razorbill; and Red-throated diver.
11.4 Description of the Existing Environment
Seabirds in the southern and eastern North Sea Relative abundance of marine avifauna 11.4.1 Extensive regional surveys (e.g. Carter et al., 1993; Stone et al., 1995), literature reviews (Stienen et al., 2007) and results from site-specific surveys as part of Round 1 and 2 wind farm EIAs; including the London Array, Thanet, Gunfleet Sands and Kentish Flats, have shown that the southern North Sea is an important area for seabirds. In particular, during the migratory period and winter months when breeding pairs from within Great Britain are joined by birds that have migrated from continental Europe. The assemblage present within and adjacent to the GWF site suggests that these regional waters are used at different times by birds (i) overwintering in the area; (ii) foraging from nearby breeding coastal colonies; and (iii) on migration during post-breeding dispersal and pre-breeding return. This section aims to capture these ecological aspects within the GWF site characterisation.
11.4.2 The avifauna of the shallow sea areas of the Outer Thames Estuary and along the east coast of the UK is typically comprised of a mixture of ‘true seabirds’ (for example: gannet, gulls and auk spp.), other species that spend part of their annual life cycle at sea (for example, divers and seaducks) and a wide range of species, such as waterfowl, waders and terrestrial passerines on seasonal migration, both to and from the UK and Continental Europe.
11.4.3 Based on the geographic, hydrographic and physical differences within the North Sea (Stone et al., 1995), the GWF study area falls into the southern and eastern North Sea. This sector reaches from Kent, across the English Channel and northwards to Norfolk, it includes much of coastal Netherlands, Belgium and Denmark, including the Kattegat, Wadden Sea and German Bight. This sector is characterised as being a shallow area of relatively low salinity which forms a distinct zone of distribution for many species. During winter, it is recorded as being the most important area in north-west European waters for divers, grebes and seaduck. Gulls are common throughout the year, with common gull and great black-backed gull most abundant in winter, lesser black-backed gull in summer, and herring gull throughout the year. The area is also important for terns in summer and auks in winter.
11.4.4 The southernmost part of the North Sea is an important corridor for seabird migration. The great majority (40-100%) of the flyway population of great skua Catharacta skua use the strait of Dover to leave the North Sea, as well
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as 30-70% of the lesser black-backed gull population (Stienen et al., 2007). The narrow entrance to the strait may act as a funnel for seabirds to become temporarily concentrated when they leave or enter the southern North Sea.
11.4.5 Table 11.13 highlights that the southern North Sea plays a key role (>10%) for at least three species found in the GWF survey area in high numbers, namely: red-throated diver, great skua, lesser black-backed gull. As part of the ongoing consultation with the SNCAs and the RSPB, Table 11.2, GWFL have been advised to consider potential SPA connectivity (both national and transboundary) in the context of the maximum forage ranges and distribution patterns of the flyway populations for those migrant species which are recorded within the GWF study area. For more details of this assessment refer to the HRA Report.
The effect of bathymetry and sea conditions on the distribution of seabirds 11.4.6 Seabird distribution is the result of a combination of interactive factors. Prey distribution is thought to be more important than physical factors, although nest site availability and foraging ranges for each species are also limiting factors (Stone et al. 1995).
11.4.7 The North Sea is mainly shallow (<100m), particularly in the southern part where depths rarely exceed 50m. This is the case within the GWF study area. These shallow areas are characterised by sand substrates or sand and gravel mixtures. The sandy conditions provide an ideal habitat for sandeels for example, which are an important dietary component for many seabirds.
11.4.8 Physical processes such as wind and weather conditions may have a seasonal effect on seabird distribution, often indirectly through prey distribution.
11.4.9 Water movements, temperature and salinity may also have an effect on accumulating prey. Mixing of waters brings nutrients to the surface which encourages phytoplankton growth and therefore zooplankton, fish, and ultimately birds. Fronts between water masses with different properties may also be highly productive for birds. Plume fronts exist at the outflow of many large rivers in the southern North Sea and the Thames (Stone et al. 1995), Section 3.6-Section 3.12, Technical Appendix 11.A.
Marine ecology 11.4.10 The impacts of the GWF on benthic invertebrates, a bird and fish prey resource, is discussed in detail in Chapter 12: Marine and Intertidal Ecology, with the conclusion that there would be no significant impacts or changes in community structure.
11.4.11 The majority of the communities found are widespread at a regional level. Most of the habitat recorded consists of a “deep Venus community” (SS.SCS.CCS.MedLumVen and SS.SMX.OMx.PoVen), Section 3.13-3.16, Technical Appendix 11.A. This biotope is not confined to the GWF site
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boundary, and has also been found outside the proposed development area during the benthic survey. It was found to be the principal biotope on the GGOWF site and the London Array site (CMACS, 2010) to the south of the GWF and GGOWF sites.
11.4.12 A common denominator of all of the biotopes / communities in the study area is that they are all adapted to surviving in turbid waters with very high levels of suspended sediments, as would be expected given the levels of natural sediment disturbance at the site (GGOWL, 2005).
The Galloper, Inner Gabbard and Outer Gabbard Sandbanks 11.4.13 Within the wider area, The Galloper, Inner Gabbard and Outer Gabbard sandbanks are important features, and potentially influence the distribution of a number of seabird species (Figure 10). The Galloper sandbank is found within the Galloper portion of the GGOWF, approximately 11.5km long and less than 1km wide. Sea depth is 20-30m in the east, and 30-50 to the west, although can decrease from 20m to as little as 2m, Figure 11.5.
11.4.14 The Inner Gabbard sandbank is approximately 16km long and found within the Inner Gabbard portion of the GGOWF. The northern end of the Inner Gabbard is subject to a large area of water turbulence. The depth of the character area is generally 20-30 m, though areas of deeper water, up to 50m, exist to the west of the area. Depth over the Inner Gabbard is reduced to 5-15m. The area is fished all year round; usually drift netting or long-lining, though limited trawling takes place.
11.4.15 The Outer Gabbard sandbank is approximately 4km long and is found within Area A of the GWF. Depths range from 2-20m in this area. The underlying geology is a mix of gravel and gravelly muddy sand over London Clay. The sand bank will be avoided by the GWF turbine layout for environmental reasons (see Chapter 5: Project Details).
Shipping and Navigation 11.4.16 The Galloper and Gabbard areas are transited by passenger ferries, bulk carriers and tankers, though shipping avoids the sandbanks (Jones et al 2004), Chapter 18 Shipping and Navigation. As a result of its proximity to the ports of Harwich and Felixstowe, the area is covered by Vessel Traffic Services (VTS), which restricts the passage of vessels to particular channels. The area is fished all year round, usually drift netting or long-lining, though limited trawling takes place. The area is also dominated by the Outer Gabbard military zone which is used by the Royal Navy for mine laying and mine countermeasure exercises.
Fish and shellfish species 11.4.17 Fish species serve as prey to seabirds, and their presence is one of the main factors behind seabird distribution throughout the North Sea. During consultation, the RSPB (Response to Scoping Report, August 2010) noted that any impacts on the early life stages of fish may have lethal effects for
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bird life due to declines in food availability.
11.4.18 The baseline characterisation in Chapter 13: Natural Fish and Shellfish Resources has identified that the GWF overlaps or is in close proximity to a number of spawning grounds including; herring Clupea harengus, cod Gadus morhua, whiting Merlangius merlangus, sprat Sprattus sprattus, sandeel Ammodytes marinus l, sole Solea solea and plaice Pleuronectes platessa, Section 3.21-3.26, Technical Appendix 11.A.
11.4.19 Sandeel are an important prey species for many seabirds, including divers and auks. They have a close association with sandy substrates into which they burrow and are largely stationary after settlement. Observations suggest that this species rarely emerges from the seabed between September and March, except in December and January when it spawns (Fisheries Research Services, 2011). Chapter 13: Natural Fish and Shellfish Resources indicates that the GWF site falls within a low intensity sandeel spawning area and nursery ground, compared to high density areas in the central North Sea, on Dogger Bank, and on the sandbank complexes off the eastern Scottish coast.
11.4.20 While shellfish species have been recorded at GWF, the area does not represent part of any significant shellfish beds in the Outer Thames Estuary. Similarly, only a small proportion of Area B overlaps with the Downs herring spawning ground. Since the 1970’s, the main Downs herring spawning grounds used have been those in the eastern Channel. The change to a small proportion of seabed at GWF is, therefore, not anticipated to have any significant implications for this stock.
Fishing Activity 11.4.21 Fishing activity may attract birds such as fulmars, gannets and gulls; as birds can obtain a substantial proportion of their diet from fishing vessels. Camphuysen et al (1993) suggested that two million seabirds in the North Sea may be supported by discards.
11.4.22 Many seabirds (gannet, terns, auks) feed on clupeids (herring, sprat), gadoids (cod, whiting, haddock), and sandeels, particularly in spawning or nursery areas. Fishing is often concentrated on the shelf and shelf edge and therefore the opportunities for scavenging are greatest here. Within the southern and east North Sea, the seas are important nursery areas for sole and herring in particular, and important spawning areas for plaice, sole, cod and sprat. Fishing is mainly for plaice and sole, but also for cod, sprat and shrimps (Stone et al. 1995).
11.4.23 The fisheries activity within the GWF site comprises mainly foreign trawling (in particular Belgian beam and Dutch beam trawling) which target the winter plaice fishery (January) (see Chapter 15: Commercial Fisheries and Technical Appendix 15.A for full details).
11.4.24 The fishing operations across the banks are predominantly subject to
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weather restrictions and the presence of fish (cod and bass) on a seasonal basis. Local consultation indicates that the fisheries for cod are subject to wide variations in seasonality with annual variations in fish location during the winter months. Alternative grounds (Inner Gabbard and Galloper banks) would be accessible to these vessels during construction of the GWF.
11.4.25 Whilst fishing activity would not be excluded within the GWF site, it is possible that trawling activity would reduce due to concerns about health and safety with the increased risk of collision with wind farm structures. This may have a subsequent impact on the marine benthos and fish, and could aid in the recovery of areas and the development of habitats of higher diversity and complexity.
11.4.26 Whilst vessels would be able to enter the GWF site during operation, there is potential for 50m exclusion zones to be implemented around the turbines, into which, access would not be permitted. Overall, the level of fishing activity would be likely to reduce, however this is difficult to quantify due to annual changes in fishing activity and quotas. In addition, consultation with some UK based operators did not indicate a reluctance to enter the GWF site once operational, however there are concerns surrounding health and safety and insurance costs (for a detailed assessment of implications for commercial fisheries see Chapter 15: Commercial Fisheries and Technical Appendix 15.A).
11.4.27 It is recognised that fishing activity has resumed at existing operational wind farm sites, albeit with some modification to practices (such as limiting activity to within a narrower range of tidal conditions), in near shore locations and largely by smaller <10m vessels (DSML, 2011).
Designated sites 11.4.28 Details of site designations and their legislative background are provided in ES Chapter 8: Nature Conservation Designations. There are no current or proposed designated sites within the turbine area boundaries of GWF and GGOWF. Although the GWF turbine areas are over 25km at the closest point, the proposed export cable route passes through the marine Outer Thames SPA. No coastal or onshore designated sites overlap with any aspect of the development, Figure 11.6.
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11.4.29 There are a number of designated sites along the coastline within the Greater Thames area from Kent to Suffolk which, although not overlapping with GWF, may have qualifying species that have been recorded during surveys within the study area. It is, therefore, possible, depending on the levels of connectivity and foraging range of qualifying species, that the development may impact the integrity of these sites.
11.4.30 A summary table of regional SPAs within the Greater Thames and the distance from GWF (turbine arrays and export cable) is shown below for all species of principal concern, Table 11.14.
11.4.31 A detailed breakdown of the qualifying species for each SPA is shown in Table A.5, Annex 1 of Technical Appendix 11.A.
Table 11.14 Coastal and Marine SPAs within the Greater Thames Region
SPA County Closest Closest Qualifying point from point from species of Turbine Cable Route principal Areas (km) concern (km)
Alde-Ore Estuary Suffolk 26.9 7.8 lesser black- backed gull, herring gull
Benacre to Easton Suffolk 43.7 14.0 - Bavents
Benfleet and Southend Essex 80.2 92.2 - Marshes
Black Water Estuary Essex 65.9 66.6 -
Breydon Water Norfolk 68.1 37.9 -
Colne Estuary Essex 54.7 56.3 -
Crouch and Roach Essex 68.0 77.8 - Estuaries
Deben Estuary Suffolk 37.1 21.9 -
Dengie Essex 62.1 67.0 -
Foulness Essex 56.1 66.9 -
Hamford Water Essex 41.9 39.4 -
Medway Estuary and Medway, 86.3 99.9 - Marshes Kent
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SPA County Closest Closest Qualifying point from point from species of Turbine Cable Route principal Areas (km) concern (km)
Minsmere-Walberswick Suffolk 34.4 0.3 -
Outer Thames Estuary Kent, 5.4 0.0 Red-throated Essex diver Norfolk, Suffolk
Stour and Orwell Estuaries Essex, 43.7 33.9 - Suffolk
Thames Estuary and Medway, 85.0 98.2 - Marshes Thurrock, Kent
Thanet Coast and Kent 50.5 75.6 - Sandwich Bay
The Sandlings Suffolk 30.8 0.4 -
The Swale Kent 75.8 93.7 -
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.32 It is evident from Table 11.14 that only two regional SPAs within the Greater Thames contain qualifying species that are found in substantial numbers within the GWF survey area: the Alde-Ore Estuary SPA (lesser black-backed gull and herring gull) and the Outer Thames Estuary SPA (wintering red- throated diver). Effects on these populations are possible as, based on recommended maximum foraging ranges, there is likely to be connectivity between the SPAs and the GWF.
11.4.33 Following consultation with the JNCC, Natural England and the RSPB in relation to the foraging ranges of key species of principle concern (notably lesser black-backed gull, gannet and great skua, Table 11.2), Table 19 in Technical Appendix 11.A shows that other species of principal concern may range more widely than within a particular geographic region such as the Greater Thames. For these species, possible connectivity with other SPAs outside the region has been considered as part of Appendix D of the HRA Report.
11.4.34 Those SPAs within mean maximum and maximum foraging range of the GWF are shown in Figures A.17 to A.28, Annex 1 of Technical Appendix 11.A. It shows that there is possible connectivity with the Flamborough Head
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and Bempton Cliffs SPA for gannet, which is an assemblage breeding species, as it lies within the mean maximum foraging range with GWF, and also four SPAs in Scotland where fulmar breeds, which are within maximum foraging range. As adult fulmar are present at breeding colonies for most of the year, the vast majority of birds encountered at the GWF site are likely to be non-breeders and not part of any SPA population, Appendix D of the HRA Report.
Species Accounts 11.4.35 This section provides an account of the relative abundance, distribution and behavioural ecology of each of the species of principle concern listed in Section 11.3.75. The importance of the GWF to each species at different times of the year is discussed in relation to the wider southern North Sea and also to SPA populations within the UK. Separate peak monthly estimates are given for winter (October to March) and summer (April to September).
11.4.36 Summary header boxes are shown for each species, which present information on:
Conservation designations and UK population trend (from JNCC, 2011); Breeding and wintering populations at international to regional level; Peak estimates from winter and summer surveys for the whole survey area and for the wind farm constituent parts; and The maximum proportion of international, national and percentage of regional populations achieved.
11.4.37 Further explanation of the species accounts can be found in Section 3d of Technical Appendix 11.A.
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Arctic skua Table 11.16 Summary of Arctic skua spatial-temporal dynamics across the GWF study area
ARCTIC SKUA BoCC Red International GB Regional Pop Winter Winter Sum m er Conservation Status Threshold Summer Pop. Threshold Pop. Winter Summer Pop. change 2000-10: -34% 50 I 40,000-140,000 P 50 2,136 P ? 0
Aerial Surveys Proportion Peak % of of GB Re gional Peak Estim ate Area Period Threshold Pop. 2004-05 (raw count) 1 (skua sp.) TH3 Aug 0.02 n/a 2005-06 (raw count) 2 (skua sp.) TH3 Nov-Dec 0.04 n/a 2007-08 (raw count) 0 GG1-4 - 0.00 n/a
Boat-based surveys Winter Sum m er Peak proportion Peak % of of GB Re gional Peak Estimate Month Peak Estimate Month Threshold Pop. GGOWF 2004-06 0 - 12 Sep-05 0.00 n/a 2008-09 GWF Survey Area 0 - 27 Aug 0.54 n/a GWF Area A 0 - 11 Aug 0.22 n/a GWF Areas B and C 0 - 0 - 0.00 n/a GWF (Areas A, B and C) 0 - 11 Aug 0.22 n/a GWF Study Area 0 - 19 Aug 0.38 n/a 2009-10 GWF Survey Area 0 - 1 Apr 0.02 n/a GWF Area A 0 - 0 - 0.00 n/a GWF Areas B and C 0 - 0 - 0.00 n/a GWF (Areas A, B and C) 0 - 0 - 0.00 n/a GWF Study Area 0 - 1 Apr 0.02 n/a I = individuals; P = pairs national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A.
Relative abundance 11.4.38 Arctic skua are thinly scattered across the North Sea from April to July, with small concentrations around breeding grounds in Orkney and Shetland (Stone et al., 1995). After the breeding season in August to October, birds begin to migrate southwards, and this is reflected with higher concentrations around the east coast of Britain. Over winter, the population is very low as birds have reached their wintering grounds off southern Africa.
11.4.39 Aerial surveys within the Greater Thames recorded very low numbers of arctic skua in all years, usually single individuals, Table 11.16.
11.4.40 Peak numbers of Arctic skua were recorded in August 2008, during their post-breeding migration southwards (Tables 29a and 29b- Technical Appendix 11.A). A peak population estimate of 27 birds was recorded within the entire survey area in August 2008 (using correction factors by Stone et al., 1995), which does not reach levels of national importance, Plot 11.1.
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11.4.41 Highest numbers were within Area A (11 individuals), and the peak population estimate for the GWF study area was 19 individuals. Smaller numbers were recorded in July and September, and only one individual was recorded the in April 2009 and 2010, likely during the northwards return migration.
Plot 11.1 Arctic skua population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold (50 individuals).
Arctic skua Population Estimates per month: GWF Survey Area 2008-10
60
50
40
30
20 No. IndividualsNo.
10
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% national threshold
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A.
11.4.42 During GGOWF surveys in 2004-06, numbers also peaked during the autumn migration, with highest estimates of seven birds in September 2004 and twelve birds in September 2005 (Banks et al., 2006). Lower numbers were again recorded in April, with two individuals in 2005. It should be noted that, due to the low numbers of Arctic skua recorded within the GGOWF study area during boat-based surveys in 2004-2006, Banks et al., (2006) followed the approach that this species could be excluded from further detailed technical assessment (for example, collision risk modelling) as part of the GGOWF EIA.
Distribution and Behaviour 11.4.43 There are no clear patterns of usage for the low numbers of individual Arctic skua recorded within the GWF study area Figure 38 and Figure 39, Technical Appendix 11.A during the boat-based surveys.
11.4.44 Within the GWF survey area, birds were recorded mainly heading in a south or south-east direction which corresponds with the southward migration during the August 2008 peak (Figure 40, Technical Appendix 11.A). A total
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of 12.5% of birds recorded were observed feeding during boat-based surveys, suggesting that the site is occasionally utilised for more than just being a part of the migration route. Kleptoparasitism was observed on one occasion, with feeding on discards also being used as a strategy.
Summary 11.4.45 Although the sample size presented in this assessment is small, results of surveys from all years show that the GWF study area is of limited importance for Arctic skua for the majority of the year, except for a small period during the autumn southward migration, and to a lesser extent, the return spring migration. With the British breeding population estimated to be just over 2,000 pairs it is possible that a proportion of birds recorded during the 2008 August peak period, may be birds that have bred in the country, although a sizeable proportion may be non-breeders, with average first breeding age to be 4-5 years (Cramp and Simmons, 2004). It has been shown that individuals leave breeding grounds during August and immediately disperse in a generally southerly direction with many Scottish birds entering the North Sea, where terns (as a potential supply of food), are more numerous than on the Atlantic coast (Cramp and Simmons, 2004). Passage through north- temperate seas generally lasts well into October, although September is the recognised peak month.
11.4.46 It is possible, that a sizeable proportion of the flyway population is filtered through the straits of Dover, although there is no evidence available, at the time of writing, to quantify this theory. It was, however, evident that the site is relatively unimportant for the species during the return spring migration, compared to the Southern and Eastern North Sea area, Plot 11.2, although this may again reflect main passages being missed by surveys, and possibly a more rapid migration northwards.
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Plot 11.2 Monthly abundance of arctic skua in 2008/09 and 2009/10 within the GWF study area, compared to the southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
11.4.47 The variation in peak numbers between years may reflect either inter-annual differences in numbers or distribution, or may reflect the limited window of the survey duration within the main migration period, which may result in the largest movements being missed, particularly in April when northwards migration of seabirds is commonly more rapid.
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Common guillemot Table 11.17 Summary of common guillemot spatial-temporal dynamics across the GWF study area
COMMON GUILLEMOT BoCC Amber International GB Regional Pop Winter Summer Winter Sum m er Conservation Status Threshold Pop. Threshold Pop. Winter Summer Pop. change 2000-10: +17% 40,000 I 2.0-2.7m 13,224 I 1,322,354 I 29,291* I 0
Aerial Surveys Proportion Peak % of Peak of GB Regional Estimate Area Period Threshold Pop. 2004-05 (Distance est. - auks) 2,851 TH3 Nov-Dec 0.22 9.7% 2005-06 (Distance est. - auks) 1,257 TH3 Nov-Dec 0.10 4.3% 2007-08 (Distance - auks.) 18,141 GG1&2 Feb 1.37 61.9%
Boat-based surveys Winter Summer Proportion Peak % of Peak Peak of GB Re gional Estimate Month Estimate Month Threshold Pop.** GGOWF 2004-06 1,771 Dec-05 533 Jul-04 0.13 6.0% 2008-09 GWF Survey Area 7,204 February 1,122 April 0.54 24.6% GWF Area A 327 February 378 April 0.02 1.1% GWF Areas B and C 1,378 February 50 April 0.10 4.7% GWF (Areas A, B and C) 1,705 February 428 April 0.13 5.8% GWF Study Area 5,559 February 898 April 0.42 19.0% 2009-10 GWF Survey Area 1,523 December 1,664 April 0.13 5.2% GWF Area A 100 February (2) 260 April 0.02 0.3% GWF Areas B and C 101 December 89 May 0.008 0.3% GWF (Areas A, B and C) 187 February (2) 325 April 0.02 0.6% GWF Study Area 879 February (2) 1,020 April 0.08 3.0% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 20-50,000 indivs. (Stienen et al. 2007). ** percentage of regional winter population only national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.48 Around 30,000 common guillemot can be found in the southernmost part of the North Sea in a given year, which equates to around 1.5-3.0% of the biogeographical population (Stienen et al., 2007). From March to June, highest densities of common guillemot in the North Sea are recorded close to the main breeding colonies, particularly in Orkney, the Moray Firth and Flamborough Head. No common guillemot breed within the greater Thames region due to the lack of suitable cliff habitats and so no separate summer population threshold is applicable. The closest breeding colonies to the GWF are at Flamborough Head and Bempton Cliffs along the north-east coast of England.
11.4.49 Densities are relatively low in the southern North Sea during this period (Stone et al., 1995). In July and August moulting and fledging occurs, and
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very high densities are found off the east coast of Scotland. In contrast, numbers in the southern North Sea remain low. In September and October, densities increase in the southern North Sea, and peak from November to February, where birds are found further offshore.
11.4.50 During all aerial surveys, the large majority of auks recorded are believed to have been common guillemot (DTI, 2006; BERR, 2007; DECC, 2009). Section 3.291 of Technical Appendix 11.A describes how peak numbers of auks were recorded during aerial surveys across the Thames Strategic Area in 2004/05, 2005/06, 2007/08 found that the peak population estimates of TH3 (Plot 11.3) regularly exceeded the regional winter population threshold, assuming the majority of birds are common guillemot. Overall numbers fell in late winter and very few bids were recorded in the summer.
11.4.51 The highest estimate from Distance analysis by DECC (2009) was of 18,900 individuals in the blocks surveyed in February (Figure 90, Technical Appendix 11.A). This population reaches national importance, assuming the majority of birds are common guillemot.
11.4.52 Common guillemot were frequently recorded during the majority of boat surveys, although none recorded numbers that reached national importance, Plot 11.3. Populations followed a similar trend to that observed from aerial surveys in the Greater Thames, with numbers being low through summer months, and increasing during the winter (Table 43a and 43b, Technical Appendix 11.A). A peak population estimate was recorded in February 2009, with an estimated 7,204 individuals recorded within the entire GWF survey area, forming around 25% of the regional population. Numbers in Area B alone reached regional importance in this month. The 1% regional threshold obtained from estimates in Stienen et al., (2007) was exceeded in most months, suggesting that numbers in the southernmost North Sea may be larger than previously thought. Surveys in 2009/10 recorded lower numbers of birds throughout the year, with a peak estimate in April 2010 of 1,664 birds (regional importance). Numbers within the GWF study area regularly exceeded regional importance during winter months.
11.4.53 For further detail on the approach to distance-based analysis of the auk observation data, refer to Section 3.288 of Technical Appendix 11.A.
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Plot 11.3 Common guillemot population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold (13,224 individuals) and 1% regional threshold (292 individuals).
Guillemot Population Estimates per month: GWF Survey Area 2008-10
14,000
12,000
10,000
8,000
6,000 No. IndividualsNo. 4,000
2,000
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% national threshold 1% regional threshold
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.54 During surveys for the GGOWF in 2004-06, numbers were lowest in May and June, when most breeding adults would have been at or near nesting colonies (Banks et al., 2006). Again, a winter peak was observed, reaching an estimated 1,771 birds in December 2005 (2.4 birds per km2). This was below the 2008/09 peak density (6.5 birds per km2) but higher than the peak in 2009/10 (1.5 birds per km2), showing that there is likely to be large variability in population distribution between years.
Distribution and behaviour 11.4.55 During aerial surveys in the Greater Thames in 2004/05, distributions varied by period; auks were widespread through most of the Thames, with the exception of TH1 (Banks et al., 2006), Figure 89 and Figure 90, Technical Appendix 11.A. The highest densities occurred in different areas through the winter, although there was a general movement offshore from mid to late winter. At the end of the summer the main concentrations were in the north of the wider Thames Estuary. In 2005/06, auks occurred widely in offshore parts of the Strategic Area, with highest concentrations in the south-east and north. In early winter, birds occurred in small concentrations over wide areas, generally offshore with no areas of high concentration.
11.4.56 Boat-based surveys in the GWF survey area showed that common guillemot
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distributions were quite even throughout all months, Figure 92 and Figure 93, Technical Appendix 11.A. During mid winter, higher concentrations of auks occurred in the south-east and north-east areas. The flock size peaked at 35 birds in January 2009. The distribution of birds in late winter was similar to that of early winter. Few birds were recorded in the summer, with no obvious distributional trends.
11.4.57 Figure 94, Technical Appendix 11.A shows that a sizeable proportion were recorded flying a north- to north-easterly direction. It is not immediately clear why such a trend exists, but it may reflect the migratory patterns of overwintering birds heading to northern colonies in Helgoland and the Baltic prior to breeding (Harris and Swann, 2002), or birds from France and Spain returning to British colonies.
11.4.58 During boat-based surveys, common guillemot were often observed in an escape dive or fly away response to the survey vessel. Around 1.5% of all common guillemot records were of birds observed actively feeding, with some records of animals carrying sandeels. These sightings were often associated with small-scale sandy upwellings which occurred ephemerally and are wide-spread throughout the GWF study area.
Summary 11.4.59 In the southern and eastern North Sea survey sector, common guillemot populations are highest during winter months, with these large populations likely to include dispersed birds from colonies across northern Europe, plus some late moulting adults (Banks et al., 2006). Densities reached a peak of 2.7 birds per km2 in February, which is moderate in comparison with other sectors further north, which peak at over 10 birds per km2 (Stone et al., 1995). The peak density within the GWF was recorded in February 2009 (6.5 birds per km2), which suggests that, at least on occasion, the area hosts relatively high numbers of common guillemot compared to the wider southern North Sea. Densities observed across the entire 2008-2010 time-series suggest that, overall; the GWF study area holds no importance for this species when compared to other offshore aerial survey sectors in the Outer Thames. However, the population of national importance recorded during aerial surveys in February-March 2008 within the Greater Gabbard survey area suggests that the site is relatively important for the species in winter.
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Plot 11.4 Monthly abundances of common guillemot in 2008/09 and 2009/10 in GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
11.4.60 Plot 11.4 suggests that common guillemot densities are lower in summer months, both within the GWF survey area and the wider southern and eastern North Sea, with peaks of 1.5 birds per km2 and 1.3 birds per km2 respectively. This is unsurprising, since the area is beyond the foraging range of common guillemot from all colonies, and suggests that the area is unimportant for the species in summer, with a peak population of 1,664 birds compared to a national breeding population of 1.3 million pairs (Baker et al., 2006). It may, however, be of some importance to the species during the post-breeding moult period.
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Common gull Table 11.18 Summary of common gull spatial-temporal dynamics across the GWF study area
COMMON GULL BoCC Amber International GB Regional Pop Winter Winter Sum m er Conservation Status Threshold Summer Pop. Threshold Pop. Winter Summer Pop. change 2000-10: ? 20,000 I 590,000-1.9m P 9,000 I 48,163 P 20,527* I 0
Aerial Surveys Peak % of Proportion of Re gional Peak Estim ate Area Period GB Thres hold Pop. 2004-05 (Distance est.) 56 TH3 Jan-Feb 0.01 0.3% 2005-06 (Distance est.) 94 TH3 Feb-Mar 0.01 0.5% 2007-08 (Raw count.) 2 GG Feb-Mar 0.00 0.01%
Boat-based surveys Winter Sum m er Peak Peak % of Peak Peak proportion of Re gional Estimate Month Estimate Month GB Thres hold Pop.** GGOWF 2004-06 35 Jan-06 3 Apr-04 0.004 0.2% 2008-09 GWF Survey Area 168 January (1) 149 April 0.15 0.8% GWF Area A 10 February 5 April 0.01 0.0% GWF Areas B and C 14 January (1) 7 April 0.01 0.1% GWF (Areas A, B and C) 14 January (1) 12 April 0.01 0.1% GWF Study Area 47 January (1) 118 April 0.12 0.2% 2009-10 GWF Survey Area 318 February (1) 120 April 0.12 1.5% GWF Area A 12 March 0 - 0.001 0.1% GWF Areas B and C 7 December 7 May 0.01 0.0% GWF (Areas A, B and C) 12 March 7 May 0.01 0.1% GWF Study Area 119 February (1) 24 April 0.02 0.6% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 45-100,000 indivs. (Stienen et al. 2007). ** percentage of regional winter population only national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.61 Between 41,000 and 100,000 common gull are estimated to migrate through the southernmost part of the North Sea each year, which accounts for around 5% of the biogeographic population of this species (Stienen et al., 2007). During the breeding season, numbers are low as birds move to their inland colonies, although there are isolated clusters of birds around the British coast where coastal colonies exist. The regional breeding population consists of three small colonies – two in Suffolk and one in Kent. Apart from a small number of pairs in Norfolk, the species is largely absent in the rest of coastal England. Generally, the number of common gull peak within the southern North Sea in October to February, with high densities noted in The Wash and the Greater Thames. From July to September, birds are scattered widely,
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reflecting the trend that breeding birds will move south to wintering areas in the southern North Sea (Stone et al. 1995). .
11.4.62 For further detail on the approach to analysis and treatment of the regional and site-specific common gull baseline datasets, refer to Section 3.186 of Technical Appendix 11.A.
11.4.63 Aerial surveys within the Greater Thames region confirm these seasonal trends (DTI, 2006).In general, numbers observed in proximity to the GWF site (TH3-Figure 11.4) were smaller than those recorded in more coastal sectors.
11.4.64 Boat-based sightings data from the entire GWF survey area suggest that peak numbers of common gull were recorded midwinter to April, in both survey years, Plot 11.5 below and Tables 33a and 33b of Technical Appendix 11.A. Total population estimates for each month were well below 1% national threshold levels, but numbers did exceed the winter regional threshold value in early February 2010, peaking at an estimated 318 individuals, most outside of the GWF study area. During the main breeding season numbers were significantly lower in both years, likely due to birds returning to inland colonies to breed.
Plot 11.5 Common gull population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% regional population threshold for winter months.
Common gull population estimates per month: GWF survey area 2008-10
350
300
250
200
150
No. Individuals No. 100
50
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month 2008-09 2009-10 1% Regional threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Distribution and behaviour 11.4.65 Common gull is a more coastal species than some of the other gulls considered in this assessment, the majority of individuals were recorded outside of the GWF study area, in more coastal waters to the west, Figure 49
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and 50, Technical Appendix 11.A.
11.4.66 The main proportion of flights recorded were in a south-east direction (Figure 51, Technical Appendix 11.A), and it is possible that this trend is reflected in the late winter when peak numbers were recorded, as continental birds that winter in Britain return to breeding colonies across Europe (Douse, 2002, DECC, 2009). As such, it is likely that the GWF area is unimportant for foraging birds, with the majority briefly passing through on longer migratory movements. Only a small proportion (around 1%) of birds during all surveys were recorded foraging within the survey area, with 19% recorded on the sea at any time. Any foraging activity recorded involved dip-feeding close to the surface.
Summary 11.4.67 The relative abundance of common gull within the GWF survey area, compared to wider southern and eastern North Sea, suggests that the area is of negligible importance to common gull in summer months, Plot 11.6. The GWF is not close to any major breeding colonies and is beyond the probable maximum foraging range of the closest small colonies in south-east England (considered to be a maximum of 15km, Ratcliffe et al., 2000). In winter months, larger numbers can be found, with the site still being of minimal regional importance. As with the regional and site-specific surveys, there is an observable peak in numbers within the wider southern and eastern North Sea during January, Plot 11.6. However, the average densities within the GWF study area are consistently much lower (0.29 birds per km2) than the wider North Sea (2.94 birds per km2 in Stone et al., 1995).
11.4.68 Evidence from Greater Thames aerial surveys suggest that during peak winter months, most common gull are more likely to forage closer to the shore, roosting on inland water bodies or coastal areas.
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Plot 11.6 Monthly abundances of common gull in 2008/09 and 2009/10 in GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Northern fulmar
Table 11.19 Summary of northern fulmar spatial-temporal dynamics across the GWF study area
FULM AR BoCC Amber International GB Regional Pop Winter Sum m er Winter Sum m er Conservation Status Threshold Pop. Threshold Pop. Winter Summer Pop. change 2000-10: +1% 15,000 I 2.8-4.4m P 9,975 I 498,764 P 4,051* I 1,984 P
Aerial Surveys Proportion Peak % of Peak of GB Regional Estimate Area Period Threshold Pop. 2004-05 (Distance est.) 376 TH3 Nov-Dec 0.04 9.3% 2005-06 (Distance est.) 242 TH3 Jan-Feb 0.02 6.0% 2007-08 (Distance est.) 1,186 GG3-4 Mar 0.12 29.3%
Boat-based surveys Winter Sum m er Peak proportion Peak % of Peak Peak of GB Regional Estimate Month Estimate Month Threshold Pop. GGOWF 2004-06 888 Oct-05 538 Jul-04 0.09 21.9% 2008-09 GWF Survey Area 2,619 January (1) 1,964 September 0.20 64.7% GWF Area A 190 January (1) 654 September 0.02 16.5% GWF Areas B and C 258 January (1) 112 July 0.01 6.4% GWF (Areas A, B and C) 448 January (1) 663 September 0.07 16.7% GWF Study Area 1928 January (1) 1715 September 0.17 47.6% 2009-10 GWF Survey Area 372 March 1,601 September 0.16 40.3% GWF Area A 37 March 113 September 0.01 2.8% GWF Areas B and C 68 October 101 September 0.01 2.5% GWF (Areas A, B and C) 82 October 214 September 0.02 5.4% GWF Study Area 292 March 1,068 September 0.11 26.9% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 10m indivs. (Stienen et al. 2007). national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.69 It is not known how many northern fulmar are present each year within the southernmost North Sea, but it is considered that only a small proportion of the biogeographic population (<0.01%) are found in this region (Stienen et al., 2007). Between March and July, fulmar are distributed widely across the southern North Sea, although numbers are relatively low compared to those recorded further north along Scottish coasts, where the majority of British colonies occur (Stone et al., 1995). From August to November, distribution extends southwards from the main breeding colonies, although numbers in the Greater Thames area are still relatively low, and this trend continues throughout the winter months. It is evident that the continental shelf edge is important for fulmar at most times of the year, with the closest area of high
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concentrations to GWF being at the Dogger Bank (Stone et al., 1995). Mitchell et al., (2004) recorded only 106 breeding pairs in the southern North Sea at the time of the Seabird 2000 survey programme, which reflects the lack of cliff-nesting habitat in south-east England. The nearest major colonies to the GWF are north of the Humber Estuary, and particularly in Orkney and Shetland.
11.4.70 For further detail on the approach to analysis and treatment of the regional and site-specific fulmar baseline datasets, refer to Section 3.120 of Technical Appendix 11.A.
11.4.71 Aerial surveys across the Thames Strategic Area in 2004/05, 2005/06 and 2007/08 estimated peak populations of regional importance in summer and late winter, Table 11.19.
11.4.72 During the site-specific boat surveys, the estimated population of fulmar within the overall survey area did not reach the 1% threshold of national importance (9,975 birds) in any months between 2008- 2010. Fulmar were recorded in numbers that comprised a sizeable proportion of regional population estimates by Stienen et al., (2007) in four months, from the post- fledging/moult period in July, to a midwinter peak in early January 2009 of 2,617 individuals, Plot 11.7, although only a small proportion were recorded within the GWF footprint. In the second half of the winter and during the main breeding season, numbers were generally much lower, but regularly exceeded the summer threshold of 50 individuals in all component parts of the GWF study area.
11.4.73 Section 3.127 of Technical Appendix 11.A suggests that, compared to the GWF surveys, the numbers of fulmar were generally lower during the GGOWF surveys in 2004-06. This may reflect the more inshore location of the GGOWF study area.
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Plot 11.7 Northern fulmar population estimates within the GWF survey area in 2008/09 and 2009/10, showing the 1% regional population threshold (50 individuals).
Fulmar Population Estimates per month: GWF Survey Area 2008-10
3,000
2,500
2,000
1,500
1,000 No. Individuals No.
500
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% regional threshold
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Distribution and behaviour 11.4.74 In accord with this species’ largely pelagic lifestyle, aerial surveys conducted within the Thames Strategic Area found the species to be largely absent in more coastal waters, recorded in higher concentrations further offshore (DECC, 2009), Figure 22, Technical Appendix 11.A. There does not appear to be a clear pattern in fulmar distribution within the GWF survey area, Figure 23 and 24, Technical Appendix 11.A.
11.4.75 Birds tended to exhibit a south-eastwards flight direction, Figure 25 of Technical Appendix 11.A. This may correspond to the southward post- breeding passage when peak numbers were recorded passing through the GWF survey area. During all boat-based surveys, only a small proportion of birds were recorded feeding within the survey area (3.9%), mainly in early January 2009. This is to be expected from such a wide-ranging, opportunistic forager. Birds were often recorded in association with fishing vessels, foraging on discards.
Summary 11.4.76 Fulmar are a common breeding bird within Britain (2.8-4.4 million breeding pairs, Baker et al., 2006), with numbers particularly high in northern Scotland. Numbers within the GWF survey area regularly exceeded regional breeding
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population levels, although no surveys revealed numbers close to the national threshold.
11.4.77 Fulmar have an extensive foraging range, with reported maximum trip distances of over 600km (BirdLife International, 2010), with a mean maximum trip of around 300km. Relative to the peak densities of the wider southern and eastern North Sea (2.17 birds per km2), western or northern isles (12 birds per km2 in Stone et al., 1995) during the breeding season, the GWF site is relatively unimportant for the species (1.75 birds per km2).
11.4.78 Within the GWF study area, Plot 11.8 suggests that there is a marked decline in densities following the end of the main breeding season, with a possible peak in September, as their distribution moves southwards from the northern breeding colonies. Data suggests the GWF site is of no particular importance for the species during the winter. It should be noted that the sharp peak discernable in December 2009 may have been in response to a concentrated food source, as the trend was not repeated in the following year, or in the wider southern and eastern North Sea.
Plot 11.8 Monthly abundances of fulmar in 2008/09 and 2009/10 in GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Gannet
Table 11.20 Summary of gannet spatial-temporal dynamics across the GWF study area
GANNET [SPA species], BoCC Amber International GB Regional Pop Winter Summer Winter Summer Conservation Status Threshold Pop. Threshold Pop. Winter Summer 300,000- Pop. change 1985-2005: +39% 3,000 I 310,000 P 4,371 I 218,546 P 10,024* I 2,552 P
Aerial Surveys Proportion Peak % of Peak of GB Regional Es t im at e Ar e a Pe r io d Threshold Pop. 2004-05 (Distance est.) 139 TH3 Oct-Nov 0.03 1.4% 2005-06 (Distance est.) 132 TH3 Oct-Nov 0.03 1.3% 2007-08 (Distance est.) 1,310 GG3&4 Feb-Mar 0.30 13.1%
Boat-based surveys Winter Summer Proportion Peak % of of GB Regional Peak Estimate Month Peak Estimate Month Threshold Pop. GGOWF 2004-06 276 Dec-05 257 Aug-05 0.06 5.0% 2008-09 GWF Survey Area 1,325 November (1) 332 September 0.30 13.2% GWF Area A 46 November (2) 79 September 0.02 1.5% GWF Areas B and C 229 November (1) 27 September 0.05 2.3% GWF (Areas A, B and C) 266 November (1) 106 September 0.02 2.7% GWF Study Area 1145 November (1) 263 September 0.26 11.4% 2009-10 GWF Survey Area 735 October 677 April 0.15 13.3% GWF Area A 136 October 67 April 0.03 1.4% GWF Areas B and C 114 October 158 April 0.03 3.1% GWF (Areas A, B and C) 250 October 225 April 0.06 4.4% GWF Study Area 479 October 479 April 0.11 9.4% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 892,000 indivs. (Stienen et al. 2007). national importance regional importance
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.79 Large numbers of gannet pass through the Dover Strait each year, with numbers estimated at 892,000 individuals by Stienen et al., (2007). This forms approximately 4-7% of the biogeographic population.
11.4.80 Highest densities of gannets in the breeding season surrounded breeding colonies further north in European waters (Stone et al. 1995), and so the southern North Sea area is relatively unimportant for the species, although it is widely distributed due to its large foraging range (over 600km according to BirdLife International 2010). The closest breeding colonies are at Bempton Cliffs in Yorkshire, and in Ortac and Les Etacs, where around 7,500 pairs of gannets nest at two long-established gannetries in the Channel Islands (Veron and Lawlor, 2009). For the remainder of the year, gannets are spread throughout offshore waters, the shelf edge and outer continental shelf are considered to be relatively important foraging areas (Stone et al. 1995).
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11.4.81 For further detail on the approach to analysis and treatment of the regional and site-specific gannet baseline datasets, refer to Section 3.137 of Technical Appendix 11.A.
11.4.82 Aerial surveys in 2004/05 counted a peak of 962 individuals in the Thames Strategic Area during October-November, the majority of which were within TH2, whereas only 39 birds were found in TH3, (DTI, 2006). Numbers were very low until July-August (78 gannet were recorded in TH3), out of a total of 152 birds sighted across the entire Thames Strategic Area. Distance calculations by Banks et al. (2006) estimated a peak population of 139 birds (95% confidence limits: 83-235) in TH3, which is of regional significance.
11.4.83 During 2005/06, large numbers of gannets were observed in the Thames Strategic Area during the winter, with a peak count of 2,404, BERR, 2007a. Similar to the previous year, by late winter/early summer low numbers occurred across the site. Distance calculations by Banks et al. (2006) estimated a peak population of 132 birds (95% confidence limits: 89-197) in TH3, which was a similar peak to the previous survey programme, and again of regional importance.
11.4.84 Aerial surveys in 2007/08 also followed a similar seasonal peak over the winter (DECC, 2009). Table 11.20, suggests that the highest relative densities were in the north of the Thames Strategic Area, around 20km east of Orford Ness, and in the south around Falls Gap, 20km north-east of North Foreland. Density calculations estimated a peak population of 1,310 birds, which is around 13% of the whole regional population.
11.4.85 Results from the boat-based data, presented in Plot 11.9, highlight that gannet were recorded within the GWF survey area throughout the year, peaking at an estimated 1,401 individuals in early November 2008. This does not approach importance in a national context, falling well short of the surrogate 1% summer threshold of 4,371 birds. However, these peak numbers form a sizeable proportion of the winter regional population of around 10,000 individuals (Stienen et al., 2007).
11.4.86 During the summer month’s numbers were relatively low, consistently falling to below 200 individuals. A discernable peak in April 2010 (677 individuals across the whole GWF survey area) may coincide the passage movements of gannet through the English Channel to their northern breeding colonies.
11.4.87 Section 3.145, Technical Appendix 11.A, highlights that surveys within the GGOWF baseline in 2004-06, recorded markedly lower numbers than in subsequent years.
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Plot 11.9 Gannet population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% regional winter population threshold (100 individuals)
Gannet Population Estimates per month: GWF Survey Area 2008-10
1,400
1,200
1,000
800
600
No. IndividualsNo. 400
200
0
v n b Jul ep o e ay Jun Aug S Oct N Dec Ja F Mar Apr M Month
2008-09 2009-10 1% regional threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Distribution and behaviour 11.4.88 Aerial surveys within the Thames Strategic Area suggest that gannet demonstrate a predominantly offshore distribution. There were no apparent trends in the inter- or intra-annual distribution of this species recorded within the GWF study area, Figure 30 and 31, Technical Appendix 11.A.
11.4.89 Around 8.8% of all birds recorded within the GWF survey area were observed to be feeding, using a number of different strategies which included plunge diving and discard foraging as part of multi-species associations with fishing trawlers. Gannet distribution within the GWF study area tended to be patchy, with large but localised aggregations likely associated with discrete fish shoals.
11.4.90 From positively-aged gannet recorded during the boat-based surveys, it appears that for most of the year the majority of birds are adults (80-90%), although the proportions of sub-adults evidently increase from the late breeding season, through to August and September, Section 3.149-3.150, Technical Appendix 11.A. This likely coincides with the autumn migration southwards, when sub-adults often leave breeding areas some weeks earlier than adults (Cramp and Simmons, 2004). It is evident that numbers in the southern North Sea increase during post-breeding months, regularly peaking
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in October as birds head southwards to overwinter in the Mediterranean and northern Africa (Mitchell et al., 2004). Throughout the winter the sub-adult proportion is low. Vernon and Lawlor (2009) observed that after their second winter, immature birds from Alderney colonies tend to summer in northern waters, often around different gannetries. By the time of the fifth year, gannet have become successful hunters with sufficient skills to cope with shorter winter days and stormy weather in more northerly latitudes, and so are more likely to remain close to the colony. This trend may be apparent in the survey area, where adults are more likely to overwinter in the North Sea than sub-adults.
Summary 11.4.91 There is a large population of gannet in Britain (around 300,000 pairs – Baker et al., 2006) although they breed at a small number of colonies found on rocky coastal stacks, with the closest to the GWF being at Bempton Cliffs in north-east England (JNCC, 2011j), and two colonies in the Channel Islands to the south-west. Although gannet can range extensively to capture food, it does not appear that the GWF area is important for the national gannet population during the breeding season, Plot 11.10. Summer abundances suggest that the GWF area is relatively important for the species in a regional context, and may be used by a limited number of breeders and wandering non-breeders.
11.4.92 Summer densities in the southern and eastern North Sea area peaked at 0.04 birds per km2 in April (Stone et al., 1995), which was lower than those recorded in the GWF survey area in 2009/10, reaching 0.61 birds per km2 in the same month. These results are, however, lower than areas around breeding colonies, particularly in the north-west Atlantic coast, which reached up to 4.81 birds per km2 near the St Kilda colony (Stone et al., 1995). It should be noted that total gannet numbers are likely to have increased substantially since the surveys presented in Stone et al., (1995), which were carried out in the late 1980s and early 1990s. It is acknowledged that the GB gannet population has increased by around 10% during the Seabird 2000 surveys.
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Plot 11.10 Monthly abundances of gannet in 2008/09 and 2009/10 in the GWF survey area, and in southern & eastern North Sea (from Stone et al., 1995).
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Great black-backed gull
Table 11.21 Summary of great black-backed gull spatial-temporal dynamics across the GWF study area
GREAT BLACK-BACKED GULL BoCC Amber International GB Re gional Pop Winter Summer Winter Sum m er Conservation Status Threshold Pop. Threshold Pop. Winter Summer 110,000- Pop. change 2000-10: -14% 4,400 I 180,000 P 400 I 17,084 P 25,117* I 4 pairs
Aerial Surveys Peak Proportion of Peak % of Es t im at e A r e a Pe r io d GB Threshold Regional Pop. 2004-05 (Distance est.) 53 TH3 Jan-Feb 0.13 0.2% 2005-06 (Distance est.) 1,450 TH3 Nov -Dec 3.63 5.8% 2007-08 (Raw count.) 19 GG1-2 Feb 0.05 0.1%
Boat-based surveys Winter Summer Peak Peak % of Peak Peak proportion of Re gional Estimate Month Estimate Month GB Threshold Pop.** GGOWF 2004-06 572 Dec-05 24 Apr-04 1.43 2.3% 2008-09 GWF Survey Area 1,308 January (1) 256 September 3.27 5.2% GWF Area A 32 January (1&2) 42 September 0.08 0.1% GWF Areas B and C 404 January (1) 17 April 1.01 1.6% GWF (Areas A, B and C) 436 January (1) 42 September 1.09 1.7% GWF Study Area 1,290 January (1) 173 September 3.23 5.1% 2009-10 GWF Survey Area 325 February (1) 114 April 0.81 1.3% GWF Area A 6 February (2) 12 April 0.02 0.0% GWF Areas B and C 104 February (2) 0 - 0.26 0.4% GWF (Areas A, B and C) 110 February (2) 12 April 0.53 0.4% GWF Study Area 307 February (1) 81 April 0.77 1.2% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 6-9,000 indivs. (Stienen et al. 2007). ** percentage of regional winter population only; national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.93 Between 6,000-9,000 great black-backed gull are estimated to migrate through the strait of Dover annually, with around 5.2% of the biogeographic population found in the southern North Sea (Stienen et al., 2007). During the breeding season, the distribution of great black-backed gull is mainly coastal, becoming more widespread across the southern and eastern North Sea in winter (Stone et al., 1995). Numbers are highest in the southern North Sea during the non-breeding season as resident birds are augmented by birds that breed in Fenno-Scandinavia and Iceland. During Seabird 2000 surveys only one small colony was present in south-east England, comprising eight pairs in coastal Suffolk.
11.4.94 For further detail on the approach to analysis and treatment of the regional and site-specific great black-backed gull baseline datasets, refer to Section 3.243 of Technical Appendix 11.A.
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11.4.95 Large numbers of gulls were recorded in the Thames Strategic Area aerial surveys, with most, including great black-backed gull, more commonly found inshore (DTI, 2006). During 2005/06 surveys, peak in October-November (the majority off the southern Kent coast), by mid-winter more birds were found in offshore blocks (TH3 had a peak count of 32 birds between January- February 2005), which equated to a population estimate of 1,450 birds (Banks et al., 2006), this is considered to be of national significance, Table 11.21.
11.4.96 As part of the boat-based surveys, the largest number of great black-backed gull were similarly recorded during winter months, reaching national importance in early January 2009 (1,308 individuals) (these records represent the December 2009 data in Plot 11.11, which was delayed until early January). During this survey, both Area B and its 0-4km buffer also reached national importance. Flocks of up to 15 birds were recorded during this month, although only five birds were recorded feeding. Numbers were also close to the national threshold within the GWF survey area in February 2009 (392 individuals). Numbers exceeded the regional winter threshold in mid-January (281 individuals) and March 2009 (260 individuals) across the whole survey area.
11.4.97 In summer, populations did not reach national significance, but using 50 individuals as a surrogate regional population threshold, the GWF survey area was of regional value in August and September 2008 (peak of 256 birds), and in April 2009.
11.4.98 In 2009/10, the population peaked at 325 individuals during early February 2010, which did not exceed the national importance threshold, but was of regional importance. This threshold was also met in mid-February and was close to in December 2009. No GWF study area component parts were of regional importance.
11.4.99 During the breeding season, populations within the whole GWF survey area were comparatively low, although did exceed the surrogate 1% regional summer threshold of 50 individuals in September 2009 (55 individuals) and April 2010 (114 individuals).
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Plot 11.11 Great black-backed gull population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold for winter months (400 individuals) and 1% regional threshold for winter months (250 individuals).
Great black-backed gull population estimates per month: GWF survey area 2008-10
1400
1200
1000
800
600
No. IndividualsNo. 400
200
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% national threshold (w inter) 1% regional threshold (w inter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.100 During GGOWF boat-based surveys, few birds were recorded in summer months (peak estimate of 24 birds in April 2004), and the pattern in winter was inconsistent (Banks et al., 2006). Few birds were recorded during the first winter in 2004, but in December 2004 a peak estimate of 405 birds reached national significance. In the third winter (December 2005), a peak of 572 birds also exceeded the 1% national threshold.
Distribution and behaviour 11.4.101 Aerial surveys in the Greater Thames indicate that great black-backed gull are more likely to be found in inshore areas during summer months, but become more marine during the winter (DTI, 2006; BERR, 2007; DECC, 2009). Within the GWF survey area, great black-backed gull were recorded in dispersed aggregations of up to 46 birds, likely in response to feeding resources such as discards or other seabirds, where kleptoparasitism may take place (Cramp and Simmons, 2004).
11.4.102 Figure 71 and 72, Technical Appendix 11.A, suggests that there was no clear pattern of great black-backed gull flights recorded in the GWF survey area; this may reflect the opportunistic feeding strategy of this species. Age class data indicates that, for most of the year, the majority of birds are adults
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(Figure 74 and 75, Technical Appendix 11.A). The proportions of sub- adults appear to increase during post-breeding and spring movements, which may reflect the earlier passages of sub-adults to and from breeding colonies further north in Europe, compared to the more sedentary adult population in Britain.
Summary 11.4.103 The numbers of great black-backed gull within the GWF study area increase from the end of the breeding season, reaching a discernable peak in December (1.17 birds per km2). At the same time, densities in the southern and eastern North Sea reach around 1.44 birds per km2, which is among the higher densities in north-western European waters during this period (Stone et al., 1995). This would suggest that, in a wider regional context, the GWF study area is not especially important for the species, Plot 11.12. The British population is largely resident, therefore this period of high densities is likely to capture the influx of birds that breed in Fenno-Scandinavia and Iceland (Stone et al., 1995).
11.4.104 As concluded by Burton et al., (2006), with up to 300,000 birds found in the North Sea as a whole during winter (Skov et al., 1995), it is debatable whether the peak estimates recorded during this period (up to 1,450 birds in aerial surveys) should be of national importance. Regardless, the GWF site as a whole is likely to be at least of regional significance in the winter.
Plot 11.12 Monthly abundances of great black-backed gull in 2008/09 and 2009/10 within GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Great skua Table 11.22 Summary of great skua spatial-temporal dynamics across the GWF study area
GREAT SKUA BoCC Amber International GB Regional Pop Winter Winter Summer Conservation Status Threshold Summer Pop. Threshold Pop. Winter Summer Pop. change 2000-10: ? ? 16,000 P 193 I 9,364 P 539* I 0
Aerial Surveys
Peak Proportion of Peak % of Estimate Area Period GB Threshold Regional Pop.** 2004-05 (raw count) 1 TH3 Nov -Feb 0.01 0.2% 2005-06 (raw count) 1 TH3 Oc t-Nov 0.01 0.2% 2007-08 (raw count) 3GG2Feb0.020.6%
Boat-based surveys Winter Summer Peak Peak Peak proportion of Peak % of Estimate Month Estimate Month GB Threshold Regional Pop.** GGOWF 2004-06 253 Oct-05 208 Sep-04 1.3 46.9% 2008-09 GWF Survey Area 30 November (2) 313 September 1.6 58.1% GWF Area A 5 November (1) 53 September 0.3 9.8% GWF Areas B and C 0 - 3 September - 0.6% GWF (Areas A, B and C) 5 November (1) 56 September 0.3 10.4% GWF Study Area 13 Nov (1) & (2) 241 September 1.2 44.7% 2009-10 GWF Survey Area 8 Oct & Feb (1) 48 September 0.25 8.9% GWF Area A 0 - 5 September 0.03 0.9% GWF Areas B and C 0 - 6 April - 1.1% GWF (Areas A, B and C) 0 - 6 April - 1.1% GWF Study Area 8 October 37 September 0.04 6.9% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 27,200 indivs. (Stienen et al. 2007). ** percentage of regional winter population only national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.105 The southern North Sea is an important migration corridor for great skua, with the majority (40-100%) of the flyway population moving through the strait of Dover to leave the North Sea, which equates to over 27,000 individuals (Stienen et al., 2007). Great skua concentrations in summer months are mainly around breeding areas in Shetland and Orkney, although non- breeders or late migrants may be seen around the English Channel (Stone et al., 1995). In July and August there are scattered sightings throughout the North Sea, indicating the start of the southward migration, which peaks in September and October. In winter there are few birds recorded, being outside of the wintering areas.
11.4.106 For further detail on the approach to analysis and treatment of the regional
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and site-specific great-skua baseline datasets, refer to Sections 3.171-3.172 of Technical Appendix 11.A.
11.4.107 Aerial surveys within the Strategic Thames Area recorded very low numbers of great skua in all years, Table 11.22.
11.4.108 Site-specific boat surveys revealed that peak numbers of great skua were observed in each year during September. The total population estimate across the GWF survey area in 2008 (313 birds) was very close to the international importance threshold of 320 individuals (1.0% of the biogeographic breeding population of 16,000 pairs (BirdLife International, 2004), Plot 11.13 below. Population estimates in August exceeded the regional 1% threshold. The peak count in 2009 of 48 birds did not reach national importance, but was close to the regional threshold of 50 individuals. A small number of birds were recorded during winter months and the spring migratory period in each year, but did not approach regional or national significance, Table 11.22.
11.4.109 The baseline GGOWF boat-based surveys in 2004-06 also experienced a similar seasonality of sightings, with estimated peaks of 208 birds in September 2004, and 254 birds in October 2005, both of national significance, Table 11.22.
Plot 11.13 Great skua population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold (193 individuals) and regional 1% population threshold (50 individuals).
Great skua population estimates per month: GWF Survey Area 2008-10 350
300
250
200
150
100 No. IndividualsNo. 50
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% GB Threshold 1% International threshold
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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Distribution and behaviour 11.4.110 Due to the relatively low numbers of great skua recorded within the Strategic Thames Area and GWF study area, patterns of usage relative to the wind farm footprint are difficult to define, Figure 43 and 44 of Technical Appendix 11.A.
11.4.111 Within the GWF survey area, birds were recorded mainly heading in a south- east direction which corresponds with the southward migration through the Dover strait during the September peaks, Plot 11.14. Only around 4% of birds recorded were observed feeding during boat-based surveys, which suggests that the site is rarely utilised for more than just being a part of the migration route southwards. During boat-based surveys, observations were made of great skua kleptoparasitising lesser black-backed gull and kittiwake, as well as scavenging discards from fishing vessels.
Summary 11.4.112 Results of surveys from all years show that, as for arctic skua, the GWF area is of negligible importance for the species for the majority of the year, except for a small period during the autumn southward migration. The September peak is likely to consist of a combination of post-breeding dispersal and passage birds (from Britain, Iceland and Svalbard) heading southwards to winter off the coasts of Spain and Africa (Tasker, 1987).
11.4.113 The great majority of the flyway population of great skua use the strait of Dover to leave the North Sea (27,200 individuals- Stienen et al., 2007), therefore, the peak population estimate of 313 individuals in the GWF survey area as a whole may reach international significance (1.1% of this flyway population).
11.4.114 As the GWF area is beyond the foraging range of great skua from Scottish colonies in the breeding season (up to 100km, BirdLife International 2010), it is unsurprising that the site is rarely used during summer months.
11.4.115 The peak density of 0.28 birds per km2 recorded in September 2008 exceeds the peak density recorded in both the following year, and in the wider South and East North Sea survey area, which reached 0.04 birds per km2 (Stone et al., 1995), Plot 11.14. This may suggest that the GWF survey area is relatively important for the species during the autumn migration, although conclusions should be treated with caution due to the difficulties in accurately recording peak movements of migratory species. Regardless, it is evident that numbers of at least national importance may pass through the site in autumn each year, although it is not known what proportion of these birds are from British breeding pairs.
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Plot 11.14 Monthly abundances of great skua in 2008/09 and 2009/10 in GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
11.4.116 There is no evidence that the GWF study area is important for Great skua during the return spring migration, although in common with other migratory species, the passage rates are more rapid during this period compared to in autumn. In summer, few juveniles return as far as Scottish waters, with attachment to colonies only usually occurring during the fifth year (Cramp and Simmons, 2004), which may at least partly account for lower return numbers in spring.
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Herring gull
Table 11.23 Summary of herring gull spatial-temporal dynamics across the GWF study area
HERRING GULL [SPA species]; BoCC Red International GB Regional Pop Winter Summer Winter Conservation Status Threshold Pop. Threshold Summer Pop. Winter Summer Pop. change 2000-10: -38% 5,900 I 760,000-1.4m 4,500 I 131,469 P 64,172* I 1,181 P
Aerial Surveys Peak % of Peak Proportion of Regional Es t im at e A r e a Pe r io d GB Threshold Pop. 2004-05 (Distance est.) 335 TH3 Oct-Nov 0.07 0.5% 2005-06 (Distance est.) 35 TH3 Oct-Nov 0.01 0.1% 2007-08 (raw count) 22 GG1-2 Feb 0.00 0.03%
Boat-based surveys Winter Summer Peak Peak % of Peak Peak proportion of Regional Estimate Month Estimate Month GB Threshold Pop. GGOWF 2004-06 1,714 Dec-05 101 May-05 0.38 2.7% 2008-09 GWF Survey Area 1,083 January (1) 156 June 0.24 6.6% GWF Area A 20 January (2) 1 June 0.004 0.0% GWF Areas B and C 262 January (1) 17 June 0.06 0.7% GWF (Areas A, B and C) 262 January (1) 18 June 0.06 0.8% GWF Study Area 1,122 January (1) 78 June 0.25 3.3% 2009-10 GWF Survey Area 429 December 94 August 0.10 4.0% GWF Area A 21 December 5 Jul, Aug & Apr 0.005 0.2% GWF Areas B and C 39 February (2) 25 May 0.01 1.1% GWF (Areas A, B and C) 49 December 25 May 0.01 1.1% GWF Study Area 382 December 95 July 0.08 4.0% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. unknown (Stienen et al. 2007). national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.117 Stienen et al., (2007) estimated that around 5% of the biogeographical herring gull population is found within the southernmost North Sea at some point during the year. Their distribution is mainly coastal during spring and summer, but expands to the whole of the North Sea in winter, where the population of resident birds is augmented by individuals from northern colonies. There are a number of breeding colonies throughout south-east England, with an estimated regional population of 2,261 pairs (Mitchell et al., 2004).
11.4.118 For further detail on the approach to analysis and treatment of the regional and site-specific herring gull baseline datasets, refer to Section 3.226 of Technical Appendix 11.A.
11.4.119 Observations from the 2004/05 and 2005/06 aerial surveys suggest the number of herring gull within the Greater Thames region peaked between
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January-February (735 individuals) and October-November (748 individuals), respectively. However, numbers in proximity to the GWF remained low throughout the winter, Section 3.228-3.229 of Technical Appendix 11.A.
11.4.120 Numbers within the GWF study area reached regional winter importance during December 2008, Plot 11.15. Sightings data also suggests that, during the breeding season, populations within the whole GWF survey area were comparatively low, although did exceed the surrogate 1% regional summer threshold of 50 individuals in three summer months in both 2008/09 and 2009/10. Numbers did not reach near national importance in any month of surveys.
11.4.121 In general, the seasonality of these peaks corresponds with the observations form the GGOWF baseline dataset (BTO, 2006), Section 3.233-3.234, Technical Appendix 11.A.
Plot 11.15 Herring gull population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% regional population threshold for winter (641 individuals) and summer (50 individuals) months.
Herring gull population estimates: GWF survey area 2008-10
1,200
1,000
800
600
400 No. Individuals No.
200
0
ul r J Jun Aug Sep Oct Nov Dec Jan Feb Ma Apr May Month
2008-09 2009-10 1% regional threshold (winter) 1% regional threshold (summer)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Distribution and behaviour 11.4.122 Aerial surveys in the Greater Thames showed that herring gull are more likely to be found within inshore areas than offshore ones (Burton et al., 2006; DTI, 2006; BERR, 2007). Within the GWF survey area, sightings were evenly distributed, Figures 63 and 64 in Technical Appendix 11.A. Flocks were often clustered together, likely in response to ephemeral feeding resources
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such as fishery discards.
11.4.123 Results from RSPB GPS tagging data in the summer of 2011 showed that of the eight birds tagged at Orfordness and Havergate Island, within the Alde- Ore Estuary SPA, none foraged offshore to any significant extent, with distribution mainly being close to the colony, along the shoreline or inland, Section 3.237 of Technical Appendix 11.A.
Summary 11.4.124 It is evident that the GWF survey area is relatively unimportant for the species in all months within the context of the South and East North Sea sector (Stone et al., 1995). Populations tend to reach a peak in December- January, likely coinciding with the influx of birds (both adults and juveniles) from more northerly breeding areas augmenting the existing populations of resident birds (Stone et al., 1995), Plot 11.16 below.
11.4.125 The species is relatively coastal throughout the year, and that the GWF is beyond regular foraging ranges of breeding or roost sites (Kubetzki and Garthe, 2003).
Plot 11.16 Monthly abundances of herring gull in 2008/09 and 2009/10 in GWF survey area, and in South & East North Sea (from Stone et al., 1995).
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Kittiwake Table 11.24 Summary of kittiwake spatial-temporal dynamics across the GWF study area
KITTIWAKE BoCC Amber International GB Regional Pop Winter Summer Winter Sum m er Conservation Status Threshold Pop. Threshold Pop. Winter Summer Pop. change 2000-10: -30% 20,000 I 2.1-3.0m P 7,337 I 366,832 P 30,467 I 369 P
Aerial Surveys Peak Proportion of Peak % of Estimate Area Period GB Threshold Regional Pop. 2004-05 (Distance est.) 1,218 TH3 Jan-Feb 0.17 4.0% 2005-06 (Distance est.) 1,153 TH3 Jan-Feb 0.16 3.8% 2007-08 (Distance est.) 2,037 GG3&4 Feb-Mar 0.28 6.7%
Boat-based surveys Winter Sum m er Peak Peak Peak proportion of Peak % of Estimate Month Estimate Month GB Threshold Regional Pop. GGOWF 2004-06 1,464 Jan-06 1,090 Jun-05 0.20 147.7% 2008-09 GWF Survey Area 2,706 January (1) 543 April 0.37 73.6% GWF Area A 372 January (1) 140 April 0.05 19.0% GWF Areas B and C 193 January (1) 32 April 0.03 4.3% GWF (Areas A, B and C) 565 January (1) 172 April 0.08 23.3% GWF Study Area 1,313 January (1) 322 April 0.18 43.6% 2009-10 GWF Survey Area 1,293 December 471 May 0.18 63.8% GWF Area A 341 December 85 May 0.05 11.5% GWF Areas B and C 80 December 37 May - 5.0% GWF (Areas A, B and C) 421 December 122 May 0.06 16.5% GWF Study Area 858 December 259 May 0.12 35.1% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. unknown (Stienen et al. 2007). national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance
11.4.126 The southern North Sea holds around 5% of the biogeographic population of kittiwake, with numbers in excess of 30,000 individuals being found here at some point during the year (Stienen et al., 2007). During April to July, kittiwake are dispersed widely around the coast of Britain, with relatively low densities throughout the southern North Sea, compared to more northerly areas, where the main breeding colonies are located (Stone et al., 1995). From August to October, kittiwake begin to disperse across the North Sea, although the predominant distribution still reflects the location of breeding colonies. From November to March, birds are dispersed over much larger areas of the North Sea, and in the southern parts, numbers peak during this period. This reflects the kittiwake’s preference for pelagic habitats in winter.
11.4.127 In south-east England, kittiwake colonies are rare, due to the lack of suitable cliff-face breeding habitats. There are two known colonies each in Suffolk and Kent; both sites have an estimated 1,598 breeding pairs. Data obtained from the Seabird Monitoring Programme Online Database suggests that the
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largest colony is at Sizewell Rigs in Suffolk, holding around 500 pairs. This colony is close to the proposed export cable route, and approximately 24km from the closest point of the offshore array boundary. The closest major British colony is at Bempton Cliffs in Humberside (~275km from the closest point of the GWF). Breeding kittiwake have a maximum foraging range of 80-120km (Humphreys, 2002).
11.4.128 For further detail on the approach to analysis and treatment of the regional and site-specific kittiwake baseline datasets, refer to Section 3.261 of Technical Appendix 11.A.
11.4.129 Aerial survey data from the Thames Strategic Area concurred with national trends, in that kittiwake were widespread across the region over the winter months (reaching regional significance in some years, whereas very few kittiwake were sighted during the summer months (DTI, 2006; BERR, 2007; DECC, 2009), Section 3.264-3.270 of Technical Appendix 11.A.
11.4.130 As part of the GWF -based surveys, the largest number of kittiwake were also recorded in the entire GWF survey area during winter months, regularly exceeding regional winter importance in different years, Plot 11.17. Numbers of kittiwake did not reach levels close to national thresholds for any survey (aerial or boat-based), Table 11.24.
11.4.131 In summer, populations were lower and also did not reach national significance. Table 11.24 and Section 3.261 of Technical Appendix 11.A, describes how in using 50 individuals as a surrogate regional population threshold, the GWF survey area was of regional value in most summer months.
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Plot 11.17 Kittiwake population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% regional population threshold for winter months (305 individuals)
Kittiwake Population Estimates per month: GWF Survey Area 2008-10
3,000
2,500
2,000
1,500
No. IndividualsNo. 1,000
500
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% regional threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.132 A similar seasonal pattern was observed during GGOWF boat-based surveys with, in general, fewer birds recorded in summer months, although a peak estimate of 1,079 birds was recorded in June 2005, which appeared to be an anomaly as summer estimates were otherwise usually less than 100 individuals.
11.4.133 In winter, the peak estimate recorded was in January 2006, and totalled 1,587 birds, which was considerably less than the 2008/09 GWF peak, although closer to that of 2009/10. Regional 1% winter thresholds were also exceeded in December 2004 and March 2005.
Distribution and Behaviour 11.4.134 Aerial surveys in the Greater Thames suggest that sightings during the winter peaks had a largely pelagic distribution, the species can range extensively during this period (Bogdanova et al., 2011). The move towards the northern breeding colonies in the summer was very marked, with notable increases around Bempton Cliffs (Figure 80, Technical Appendix 11.A).
11.4.135 Within the GWF survey area, distribution was generally spread evenly throughout the year, with no obvious patterns, Figure 82 and 83, Technical Appendix 11.A.
11.4.136 Figure 84, Technical Appendix 11.A suggests that a large proportion of kittiwake flights recorded with the GWF study area were in a north-
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west/south-east axis which might reflect migration patterns southwards during the autumn, or on return during the spring. Alternatively, some birds may be travelling from breeding colonies on the English coastline during summer months to feed further offshore, or continental birds may be crossing the North Sea towards Britain.
11.4.137 From positively-aged kittiwake recorded during boat-based surveys in 2008/09 and 2009/10, it was evident that, throughout the year, the majority of birds are adults (around 85% in 2008/09 and 88% in 2009/10), Figure 85 and 86, Technical Appendix 11.A.
11.4.138 During boat-based surveys, only around 2-3% of all observations involved kittiwake feeding within the GWF survey area. This involved flocks of up to 35 individuals. Evidence suggested that birds adopted a variety of tactics to obtain food, including scavenging following fishing vessels, dip-feeding and plunge diving. Occasionally, birds were recorded roosting on turbine bases and landing on vessels, Section 3.280 of Technical Appendix 11.A.
Summary 11.4.139 Boat-based and aerial sightings data indicate that kittiwake do use the GWF site throughout the year. Numbers were generally higher in winter months as birds disperse from northerly breeding colonies into the wider North Sea.
11.4.140 Plot 11.18 shows that population of kittiwake in the southern North Sea increase sharply during the post-breeding months (September to November) and generally peak in December, with densities in the southern and eastern North Sea survey sector averaging 1.84 birds per km2. These are among the higher densities in north-western European waters during this period, although smaller than densities around Shetland and the north-west Atlantic (up to 7.3 birds per km2) (Stone et al., 1995).
11.4.141 Densities within the GWF study area during the early part of the breeding season (0.2-0.3 birds per km2) were similar to the southern and eastern North Sea average (0.42-0.49 birds per km2) in both the 2008/09 and 2009/10 monitoring period, Plot 11.18. Kittiwakes are scarce breeders in south-east England, due to the lack of suitable cliff habitat. Small populations do exist in the area on the coastal towers at Sizewell Power Station and at Lowestoft Harbour. Peak counts of around 500 birds in April- May in 2009 and 2010, and over 1,000 birds in the GGOWF survey area in June 2005 are, therefore, likely to consist of more birds than the estimated regional breeding population of 1,598 pairs (Mitchell et al., 2004).
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Plot 11.18 Monthly abundances of kittiwake in 2008/09 and 2009/10 in GWF survey area, and in southern & eastern North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Lesser black-backed gull
Table 11.25 Summary of lesser black-backed gull spatial-temporal dynamics across the GWF study area
LESSER BLACK-BACKED GULL SPA species, BoCC Amber International GB Regional Pop Winter Winter Summer Conservation Status Threshold Summer Pop. Threshold Pop. Winter Summer 300,000- Pop. change 2000-10: -36% 5,500 I 350,000 P 500 I 110,101 P 28,788* I 3,520 P
Aerial Surveys Peak % of Proportion of Regional Peak Estimate Area Period GB Threshold Pop. 2004-05 (Distance est.) 26 TH3 Jan-Feb 0.05 0.1% 2005-06 (Distance est.) 15 TH3 Jan-Feb 0.03 0.1% 2007-08 (raw counts) 26 GG1-2 Feb 0.05 0.1%
Boat-based surveys Winter Summer Peak proportion Peak % of Peak Peak of GB Regional Estimate Month Estimate Month Threshold Pop. GGOWF 2004-06 2,399 Dec-05 1,579 May-05 4.80 22.4% 2008-09 GWF Survey Area 1,540 March 3,144 June 1.43 44.7% GWF Area A 366 February 1,124 June 0.73 16.0% GWF Areas B and C 2,027 January (1) 494 July 4.05 7.0% GWF (Areas A, B and C) 2,047 January (1) 641 July 4.09 9.1% GWF Study Area 2,794 January (1) 2,618 June 5.59 37.2% 2009-10 GWF Survey Area 1,676 December 2,238 July 3.35 31.8% GWF Area A 84 February (2) 402 July 0.18 5.7% GWF Areas B and C 494 February (2) 847 June 0.99 12.0% GWF (Areas A, B and C) 578 February (2) 1,001 June 1.16 14.2% GWF Study Area 1,500 December 1,811 June 3.00 25.7% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. = 125,000 indivs. (Stienen et al. 2007). national importance regional importance
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.142 The southernmost part of the North Sea is an important corridor for lesser black-backed gull, with an estimated 30-70% of the flyway population using the strait of Dover to leave the North Sea; equating to around 125,000 birds (Stienen et al. 2007).
11.4.143 Lower densities of birds remain in the southern North Sea from November to February, and in March numbers increase, reflecting the onset of the spring migration. There are a number of breeding colonies on the south-east coast of England with, in total, 7,381 coastal pairs (Mitchell et al. 2004). The largest recorded during Seabird 2000 were both in Suffolk, with 5,500 pairs at Orfordness and 750 roof-nesting pairs at Lowestoft. Further north, 1,378 pairs were recorded at Outer Trial Bank, an artificial island in The Wash off the Lincolnshire coast.
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11.4.144 Since the SPA citation date, the colony at the Alde-Ore Estuary SPA has decreased considerably, based on the most recent data (2010) for the two main colonies within the SPA. It now supports approximately 1,603 breeding pairs (RSPB and Landguard Bird Observatory data).
11.4.145 For further detail on the approach to analysis and treatment of the regional and site-specific lesser black-backed gull baseline datasets, refer to Section 3.205 of Technical Appendix 11.A.
11.4.146 Aerial surveys found that large numbers of gulls occurred throughout the Thames Strategic Area, with most, including lesser black-backed gull being commonly found inshore (DTI, 2006). Numbers in the Greater Thames peak during the summer breeding period, with numbers low throughout the winter (Table 11.25).
11.4.147 During the 2008-2010 boat surveys, nationally-important numbers of lesser black-backed gull were recorded in both survey years, with a peak population estimate of 3,144 birds in June 2008 (1.4% of national breeding population), and 2,238 birds in July 2009 (1.0% of national breeding population). During this post-breeding period, numbers within the GWF study area regularly exceeded the regional summer threshold, Tables 35a and 35b, Technical Appendix 11.A.
11.4.148 In winter, numbers exceeded the 1% national winter threshold of 500 birds in December, February and March of both survey years, Plot 11.19.
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Plot 11.19 Lesser black-backed gull population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% national population thresholds for winter (500 individuals) and summer (2,200 individuals) months.
Lesser black-backed gull Population Estimates per month: GWF Survey Area 2008-10
3,500
3,000
2,500
2,000
1,500
No. Individuals No. 1,000
500
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% national threshold (summer) 1% national threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.149 During GGOWF surveys in 2004/05, peak summer numbers did not exceed the national summer threshold, with an estimated peak of 780 birds in June 2004, and 1,579 birds in May 2005. Conversely, in winter months, numbers were higher than in 2008-10, with peaks of 1,508 birds in March 2005, and of 2,399 birds in December 2005, which was of national importance. The 1% national winter threshold was also exceeded in October 2005 (874 birds) and February 2006 (695 birds).
Distribution and behaviour 11.4.150 Within the GWF survey area, lesser black-backed gull distribution was often concentrated in ephemeral large aggregations, most likely in response to increased prey resources, for example, discards from trawlers working in and passing through the GWF survey area. There was no apparent pattern to the location of these aggregations, Figures 55 and 56, Technical Appendix 11.A.
11.4.151 Figure 57, Technical Appendix 11.A, indicates that a large number of the lesser black-backed gull flights were recorded in a south-easterly direction through the GWF survey area. This trend may be a reflection of passage animals migrating southwards through this part of the North Sea. Alternatively, some birds may be travelling from breeding colonies on the English coastline during summer months to feed further offshore.
11.4.152 Around 10% of all lesser black-backed gull within the GWF study area were
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recorded feeding. During boat-based surveys, large flocks of 50-100 birds were commonly sighted, reaching a peak of over 500 birds in June and August 2008. Survey notes observed that flocks were commonly associated with trawler activity. Observations of birds landing on adjacent wind farm infrastructure, such as GGOWF turbine bases and meteorological masts, was also common.
Summary 11.4.153 In the southern and eastern North Sea, numbers were low during winter months, but increased from February onwards, when birds return north to breeding colonies. Stone et al. (1995) recorded a peak density of 1.65 birds per km2 in May. Peak densities in the GWF survey area were recorded in June 2008 (2.8 birds per km2) and July 2009 (2.0 birds per km2), which suggests that the site is relatively important for birds during the breeding season, compared to the surrounding southern and eastern North Sea, Plot 11.20. Over the summer months, the vast majority of birds recorded were adults, suggesting peak activity may be in relation to breeding pairs obtaining food for young birds still at breeding colonies along the east coast of England, and possibly from colonies in the Netherlands, Belgium and France, which are within maximum foraging ranges of up to at least 80km (Rock, 2002). The large population estimates are likely to be due to concentrated flocks of birds taking advantage of food resources such as fishing discards.
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Plot 11.20 Monthly abundances of lesser black-backed gull in 2008/09 and 2009/10 in GWF survey area, and in South & East North Sea
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
11.4.154 In both 2008/09 and 2009/10, population densities recorded during winter months were consistently higher in the GWF compared to the larger southern and eastern North Sea, Plot 11.20. This suggests that the site is relatively important for the species in winter months as well. It is possible that the observations are a reflection of greater numbers of birds wintering in the North Sea in recent years (i.e. after Stone et al. 1995), or returning from more southerly areas earlier in the year. It is not clear as to the origins of wintering birds, but it is likely that a combination of local breeders, non- breeders and those from colonies in more northerly latitudes are found here. Winter dispersal of juveniles is likely to be overland, and so will not often involve the GWF survey area, although birds that originate from breeding areas in Scandinavia and western Europe that overwinter in Britain may cross the site (Banks et al. 2006).
11.4.155 It is evident that large flocks of lesser black-backed gull and other gull species are found in the GWF study area in response to foraging opportunities, which includes regular association with the location of fishing vessels and their discards. However, together, the evidence does imply that the GWF is within a larger more important area for the lesser black-backed gull biogeographical population throughout the year.
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Razorbill
Table 11.26 Summary of razorbill spatial-temporal dynamics across the GWF study area
RAZORBILL BoCC Amber International GB Regional Pop Winter Winter Conservation Status Threshold Summer Pop. Threshold Summer Pop. Winter Summer 430,000- Pop. change 2000-10: +1% 5,000 I 770,000 P 1,645 I 164,492 I 6,161* I 0
Aerial Surveys Peak % of Peak Proportion of Regional Pop. Estimate Area Period GB Threshold (auks)* 2004-05 (Distance est. - auks) 2,851 TH3 Nov-Dec 1.73 13.1% 2005-06 (Distance est. - auks) 1,257 TH3 Nov-Dec 0.76 5.8% 2007-08 (Distance - auks.) 18,141 GG1&2 Feb 11.03 83.6%
Boat-based surveys Winter Summer Peak Peak % of Peak proportion of Regional Estimate Month Peak Estimate Month GB Threshold Pop.** GGOWF 2004-06 1,411 Nov-04 65 Apr-06 0.86 22.9% 2008-09 GWF Survey Area 2,187 February 136 April 1.3 35.5% GWF Area A 273 January (2) 9 May 0.2 4.4% GWF Areas B and C 242 February 21 Apr & May 0.15 3.9% GWF (Areas A, B and C) 342 February 30 May 0.2 5.6% GWF Study Area 1,701 February 142 April 1.0 27.6% 2009-10 GWF Survey Area 569 February (2) 587 April 0.35 9.2% GWF Area A 100 February (2) 97 April 0.06 1.62% GWF Areas B and C 63 February (1) 10 Apr & Sep 0.09 1.02% GWF (Areas A, B and C) 147 February (2) 107 April 0.09 2.39% GWF Study Area 360 February (1) 472 April 0.22 5.8% I = individuals; P = pairs; * resident southernmost North Sea pop. Migratory pop. 4-10,000 indivs. (Stienen et al. 2007). ** percentage of regional winter population only national importance regional importance Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.156 The southernmost North Sea is host to around 1-2% of the biogeographic population of razorbill at some point in a given year (Stienen et al., 2007). Between 4,000-10,000 individuals migrate through the strait of Dover annually. From April to July the distribution of razorbill is mainly around coastal colonies from Flamborough Head northwards (Stone et al., 1995). Numbers are low in the southern North Sea and remain so until October when birds are more widely distributed. This distribution continues throughout the winter months.
11.4.157 For further detail on the approach to analysis and treatment of the regional and site-specific razorbill baseline datasets, refer to Section 3.304 of Technical Appendix 11.A. It should be noted that distance sampling was possible for all boat-based surveys, as identification to species level was usually possible. However, during aerial surveys, auks are seldom identified to species level, and so all population estimates referred to here are based
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on combined auk observations.
11.4.158 Within the TH3 and Greater Gabbard survey blocks (Figure 11.4) it was evident that auks were present in high numbers during winter periods. The boat-based survey data from 2008-2010 was used to ground truth the broad- scale aerial data: It was calculated that, as ~20% of all boat-base auk records were of razorbill, 3,629 birds from the peak aerial estimate (n=18,141) are likely to be razorbill. This seasonal population is above the national threshold, Table 11.26.
11.4.159 Razorbill are commonly associated with common guillemot, and individuals were frequently recorded collectively during all surveys. Populations followed a similar trend to that observed from aerial surveys in the Greater Thames, with numbers of auk being low throughout summer months, increasing during the winter, Plot 11.21. Although razorbill made up the minority of auk sightings, peak estimates in the whole GWF survey area in February 2009 exceeded national importance (2,187 individuals), Table 11.26. During this month, all constituent parts of the GWF study area recorded populations of regional importance. The 1% regional threshold obtained from estimates in Stienen et al., (2007) was exceeded in all winter months, suggesting that razorbill numbers in the southernmost North Sea may be larger than previously thought. Surveys in 2009/10 recorded lower numbers of birds throughout the year, except for October and April, with a peak estimate of 587 birds in April, Plot 11.21.
11.4.160 Razorbill were largely absent in the GWF survey area from May to September, which coincides with the main breeding season, Plot 11.21.
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Plot 11.21 Razorbill population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold (1,645 individuals) and 1% regional threshold in winter (61 individuals).
Razorbill Population Estimates per month: GWF Survey Area 2008-10
2,500
2,000
1,500
1,000 No. IndividualsNo.
500
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 1% national threshold 1% regional threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.4.161 Boat-based surveys for the GGOWF showed that, again, razorbill were almost entirely absent during summer months. The peak estimate of 1,411 individuals was recorded during November 2004, with a similar number in the following month (BTO, 2006), and this fell below the national threshold. Population estimates did, however, again regularly exceed the regional winter threshold in both winters, although inter-annual variation, as in 2008- 10, was in evidence, with considerably higher numbers in March 2005 compared to March 2004 for example.
Distribution and behaviour 11.4.162 During aerial surveys in the Greater Thames in 2004/05, distributions varied by period; auks were widespread through most of the Thames, with the exception of TH1. The highest densities occurred in different areas through the season, though there was a general movement offshore from mid to late winter. At the end of the summer the main concentrations were in the north of the Thames area. In 2005/06, auks occurred widely in offshore parts of the Strategic Area, with highest concentrations in the south-east and north. In early winter, individuals occurred in small concentrations over wide areas, generally offshore with no areas of high concentration. During mid winter higher concentrations of auks occurred in the south-east and north-east areas. Low numbers of auks were recorded in the summer, with no obvious distributional trends.
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11.4.163 The rose chart for razorbill flight directions, Figure 100, Technical Appendix 11.A shows a similar pattern to that of common guillemot in that a sizeable proportion were recorded flying in a north- to north-easterly direction. This may again reflect the migratory patterns of overwintering auks heading to northern colonies prior to breeding, or birds from further south returning to British colonies.
11.4.164 During boat-based surveys, razorbill were often observed to escape dive or fly away in response to the survey vessel. Razorbill mainly obtained food by diving, and on one occasion were included a brief feeding frenzy with gannet, great black-backed gull, kittiwake and common guillemot. Around 8-9% of all razorbill records were of birds feeding, which was a greater proportion than common guillemot, although flock sizes were smaller, peaking at eight birds in February 2009.
Summary 11.4.165 The southernmost part of the North Sea holds around 1.3-2.0% of the biogeographic population of razorbill, with a total of around 4,000-10,000 individuals travelling through the strait of Dover throughout each year (Stienen et al., 2007).
11.4.166 In the southern and eastern North Sea, razorbill populations are highest during the winter months, notably between October and March. These large aggregations are likely to include dispersed birds from colonies across northern Europe (Carter et al., 1993). There was a clear peak in density during November, where 5.4 birds per km2 were estimated (Stone et al., 1995). In this month, and December, densities were the highest recorded in north-west European waters throughout the year, although it was evident from distribution maps that the main population source is in Danish waters in the Kattegat.
11.4.167 Plot 11.22 shows a second peak of razorbill numbers around February, likely coinciding with northwards movements back to colonies. During this period, estimated populations reached national importance during February 2009 (33% above the 1% threshold value), and a density of 2.0 birds per km2, which was similar to the mean density in the South and East North Sea during this period. Aerial surveys in the Greater Gabbard survey area in February 2008 also recorded similar densities which suggest that the site is of some importance for the species during this brief period, before numbers tail off into March and April.
11.4.168 During summer months, numbers are very low as adults are normally found close to their breeding colonies, with little post-breeding dispersal of juveniles or adults until October (Merne, 2002). The GWF site is, therefore, of low importance to the species during the breeding season, as no colonies are found within the species’ maximum foraging range of 20-30km (Furness and Tasker 2000; Thaxter et al., 2010).
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Plot 11.22 Monthly abundances of razorbill in 2008/09 and 2009/10 in GWF survey area, and in South & East North Sea.
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A and Stone et al., 1995.
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Red-throated diver Table 11.27 Summary of red-throated diver spatial-temporal dynamics across the GWF study area
RED-THROATED DIV ER SPA species, Annex I and Schedule 1 (breeding); BoCC Amber International GB Regional Pop Winter Winter Sum m er Conservation Status Threshold Summer Pop. Threshold Pop. Winter Summer increase (Dillon et al. (2009) 3,000 I 32,000-92,000 P 170 I 1,255 P* 7,998 I** 0
Aerial Surveys Peak % of Proportion of Regional Peak Estimate Area Period GB Thre shold Pop.*** 2004-05 (Distance est.) 98 TH3 Jan-Feb 0.58 1.2% 2005-06 (Distance est.) 729 TH3 Feb-Mar 4.29 9.1% 2007-08 (Distance est.) 253 GG3&4 Mar 1.49 3.2%
Boat-based surveys Winter Sum m er Peak % of Peak Peak Proportion of Regional Estimate Month Estimate Month GB Thre shold Pop.*** GGOWF 2004-06 120 Jan-06 68 Apr-06 0.71 1.5% 2008-09 GWF Survey Area 204 February 0 - 1.20 2.6% GWF Area A 21 March 0 - 0.00 0.0% GWF Areas B and C 60 March 0 - 0.00 0.0% GWF (Areas A, B and C) 81 March 0 - 0.00 0.0% GWF Study Area 112 March 7 April 0.00 0.0% 2009-10 GWF Survey Area 71 March 2 April 0.42 0.9% GWF Area A 8 February (1) 0 - 0.00 0.0% GWF Areas B and C 22 February (2) 0 - 0.00 0.0% GWF (Areas A, B and C) 23 February (2) 0 - 0.00 0.0% GWF Study Area 65 March 2 April 0.00 0.0% I = individuals; P = pairs; * from Dillon et al. (2009); ** from BERR (2007); *** percentage of regional winter population only Migratory pop. = 10-15,000 indivs. (Stienen et al. 2007). national importance regional importance
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Relative abundance 11.4.169 Between 13-20% of the biogeographic population of red-throated diver are found within the southern North Sea, with 10-15,000 birds migrating annually through the Dover strait (Stienen et al., 2007). From April to September, diver density in the North Sea is low, with any birds recorded in April or May being found in coastal waters (Stone et al., 1995). In October and November, numbers increase following the breeding season, with birds recorded along the eastern coast of Britain, particularly in The Wash.
11.4.170 An estimated 17,000 red-throated diver winter around Britain. Around 60% of that total are found off the south-east and east coast of Britain, largely between Flamborough Head and Kent (O’Brien et al., 2008). This population comprises birds from the UK breeding population (the majority of which are from the north of Scotland, particularly Shetland), supplemented by numbers from Scandinavia and a smaller number from Greenland (Maclean et al., 2007), Section 3.82 of Technical Appendix 11.A.
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11.4.171 Red-throated diver are largely absent from the Thames Strategic Area in summer as breeding areas are well beyond maximum foraging range.
11.4.172 Aerial surveys in 2004/05 estimated a total red-throated diver population in the Thames Strategic Area of 5,634 individuals (confidence limits of 4,485- 6,595) (DTI, 2006). In TH3 (the survey block that overlaps with GWF and GGOWF), numbers of red-throated diver peaked at 22 birds during January- February, which is low compared to those further inshore. Distance estimates by Banks et al. (2006) produced a peak population of 98 birds in TH3 in January-February of 2004-05, which is considered to be of regional importance, Table 11.27. Estimates for inshore areas over a similar period were estimated to be of national importance, Section 3.83-3.98 of Technical Appendix 11.A. The following winter (2005/06), peak estimates of 729 birds in TH3 were noted of national importance by Banks et al. (2006), Table 11.27.
11.4.173 Aerial surveys were undertaken in 2007-08 in the Greater Gabbard Area (GG1-4) during mid-late winter, during which moderate numbers of divers were recorded in the north of the survey block. Whereas surveys conducted inshore (TH1) held comparatively large numbers of red-throated diver, distributed over shallow intertidal sand banks around the Estuary mouth. The Greater Gabbard blocks were surveyed in mid-late winter, with 51 (GG1 and GG2 combined) and 124 (GG3 and GG4 combined) divers recorded respectively. In mid-winter these were located in the north and west of the study area, between Kentish Knock and The Galloper sand bank, and north of the Inner Gabbard sand bank. By late-winter the majority of sightings were in an area around the Outer Gabbard sand bank stretching north and west. Distance calculations carried out by RPS for the purposes of this assessment on GG1-4 aerial survey blocks estimated a peak population of 253 divers (all species, but likely to be all red-throated diver) in March, which is considered to be of national importance, Table 11.27.
11.4.174 Boat-based surveys within the GWF study area in February 2009 were also considered to exceed the 1% threshold for national importance, Plot 11.23. During March 2008, numbers were close to 1% significance within a regional context (70 individuals).
11.4.175 No constituent parts of the GWF in isolation, or combined to form the GWF study area held populations that reached regional significance, although numbers were high in March 2009, with the majority in Areas B and C (60 individuals)
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Plot 11.23 Red-throated diver population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% national population threshold for winter months (170 individuals) and 1% regional threshold for winter months (80 individuals)
Red-throated diver Population Estimates per month: GWF Survey Area 2008-10 250
200
150
100 `
50 No. IndividualsNo.
0
g p t Jul u ov an ay Jun A Se Oc N Dec J Feb Mar Apr M Month
2008-09 2009-10 1% national threshold (winter) 1% regional threshold (winter)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Distribution and behaviour 11.4.176 Within the Strategic Thames Area, the highest densities were recorded in the mid channel in the outer part of the estuary and off the Suffolk coast. These two areas were characterised by the presence of sizeable flocks, often comprising groups of tens of birds, and appeared to show clumped patterns associated with the channels and sand banks with the south-west to north- east trending bathymetric features of the Thames Estuary.
11.4.177 At its closest point, the GWF is approximately 27km from the Suffolk shore, generally in depths of 30-40m, reaching 50m in places, which is outside the main distribution area of red-throated diver within south east England (10- 20km from the shore taken from DTI, 2006; DECC, 2009; Webb et al. 2009). This would suggest that the GWF site is sub-optimal habitat for divers. Figure 13 and 14 of Technical Appendix 11.A suggest that there are no obvious consistent areas of red-throated diver activity within the GWF study area, with birds more prominent in western waters nearer the coast. This distribution may be accentuated by the presence of shallower sandbanks within the GGOWF survey area.
11.4.178 Population estimates from boat-based surveys in 2008-10 suggest that for the majority of the winter the GWF site holds small numbers of red-throated
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diver, with temporal peaks during the main migratory period in February and March when the species is more widespread. It is, therefore, likely that at least some of the individuals observed within the GWF study area during this period do not overwinter in the Outer Thames SPA, but in areas further south.
11.4.179 Observations from the boat-based surveys suggest that no birds were observed feeding within the GWF study area throughout the 2008-2010 survey period. Mindful of the fact feeding behaviour may be difficult to observe if birds dive beneath the surface to capture prey or disturbed by the boat’s presence, it remains unlikely that these offshore waters represent an important foraging site for red-throated divers in comparison to inshore waters.
Summary 11.4.180 Aerial surveys across Britain recorded 44% of all wintering red-throated diver in the Thames Strategic Area, with highest numbers south of the GWF site and within the Outer Thames SPA. It is evident that the Thames Strategic Area and South and East North Sea areas are unimportant for red-throated diver in summer months, Plot 11.24, as the species breeds in northern Europe in inland lochs and lochans, using only the coastline in the vicinity of breeding sites (BWPi).
11.4.181 During GWF boat-based surveys, peak densities within the GWF survey area reached 0.18 birds per km2 in February 2009, suggesting the site has no particular importance for red-throated diver during the winter, within the context of the wider southern and eastern North Sea, Plot 11.24. In comparison, Gill et al. (2004) calculated a peak winter density of 0.46 per km2 for unidentified divers and 0.23 per km2 for red-throated diver in the area surrounding the Kentish Flats Offshore Wind Farm, which is located within the Outer Thames SPA and closer to the shore.
11.4.182 In the process of determining the extent of the Outer Thames SPA, the boundary setting protocol used a density threshold of 0.62 birds per km2 (from aerial surveys) with areas above this concentration recommended for inclusion (JNCC and Natural England, 2010). Densities recorded within the TH3 aerial and GWF boat-based surveys do not consistently reach these levels.
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Plot 11.24 Monthly abundances of red-throated divers in 2008/09 and 2009/10 in GWF survey area, and of all diver species in South & East North Sea (from Stone et al., 1995). Number of red-throated divers recorded in transect per km are also shown.
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Species sensitivity in relation to conservation value
11.4.183 Assessing the sensitivity of each species of principle concern (‘receptor’) requires evaluating the population found within the GWF survey area or study area against three main factors: (i) the conservation status of the species at the relevant geographical levels, based on, Table 11.6; (ii) the population trends over the long-term at a national level, based on Table 20, Technical Appendix 11.A; and (iii) the potential connectivity with SPAs in the UK and Europe.
11.4.184 The third of these, possible connectivity with breeding, staging and wintering SPAs, is further investigated in Section 4.22-Section 4.65 of Technical Appendix 11.A and Appendix D of the HRA Report.
11.4.185 The UK holds around 5% of the biogeographical population of breeding Arctic skua, although numbers within the GWF survey area did not reach importance levels at any point (<50 individuals). However, the species is in significant decline (>25%) at a national level, and a large proportion of the UK SPA population is likely to migrate through the North Sea (and potentially the GWF survey area), Arctic skua is considered to be of International value.
11.4.186 Numbers of breeding common guillemot in the UK are high (over 1.3m
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pairs – Baker et al. 2006), although due to the lack of suitable habitat, south- east England is unimportant for the species in summer months. In winter however, populations exceeding regional significance in the context of the southern North Sea were recorded, and likely approached national significance in the larger Greater Gabbard aerial survey area. Although unlikely, SPA connectivity with the assemblage population at Cap Gris-Nez cannot be completely ruled out and therefore as a precaution, the species is considered to be of National value.
11.4.187 Although south-east England is unimportant for the species compared to national breeding populations (48,000 pairs - Baker et al. 2006), regionally- important numbers of Amber-listed common gull were found within the wider GWF survey area. As a precautionary measure therefore, the species is considered to be of Regional value.
11.4.188 A large breeding population of fulmar resides in the UK (2.8-4.4m pairs – Baker et al., 2006). Numbers within the GWF survey area did not reach national significance, but as the species is of international importance in the UK, and found regularly in regionally-important numbers in the GWF study area, fulmar is considered to be of Regional value.
11.4.189 The UK holds internationally-important breeding numbers of gannet (around 218,000 pairs – Baker et al. 2006). Although the UK population is increasing, the country holds internationally-important populations of the species and regionally-important numbers of birds were regularly recorded within the GWF survey area. It was considered that the GWF site does not form an important part of the foraging range of any SPA-designated colony, and gannet is therefore considered to be a receptor of Regional value.
11.4.190 Great black-backed gull is recorded in nationally-important numbers within the GWF during the winter period. Although not connected to any SPAs, it is considered to be of National Value.
11.4.191 A significant proportion of the biogeographical and UK SPA populations of breeding great skua are found on migration in the North Sea, and numbers within the wider GWF survey area reached national importance during autumn migration, indicating that some of these birds are from SPAs. The species is therefore considered to be of International value.
11.4.192 Herring gull was recorded in regionally-important numbers on only one occasion within the wider GWF survey area. However, as the species has shown a significant decline in numbers at a national level (>25%) and is part of the cited seabird assemblage for the Alde-Ore Estuary SPA, it is considered to be of National value.
11.4.193 The UK is home to a large population of breeding kittiwake (366,832 pairs – Baker et al. 2006). The south-east is considered relatively unimportant for the species in summer months, however, numbers in the wider GWF survey area appear to reach regionally-important thresholds. The species has also
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shown a long term significant decline in national population (>25%) albeit from a high initial figure. Therefore the species is considered to be of Regional value.
11.4.194 Lesser black-backed gull is a qualifying species of the nearby Alde-Ore Estuary SPA during the breeding season, and was recorded in nationally- important numbers within the GWF site in both summer and winter months (Tables 35a and 35b). It is therefore a receptor of International value.
11.4.195 The south-east of England is not important for razorbills during summer months, but in the winter numbers increase, reaching national significance in the wider GWF survey area. As such, the species is considered to be of National value.
11.4.196 Red-throated diver is an Annex I and Schedule 1 listed species, and is a qualifier of the nearby Outer Thames SPA during winter months. It is therefore a receptor of International value.
11.4.197 A summary of receptor sensitivity in relation to the conservation status of national, regional and local populations relevant to the GWF is shown in Table 11.28.
Table 11.28 Receptor sensitivity in relation to conservation value
Sensitivity Species
International Red-throated diver, great skua, lesser black-backed gull, Arctic skua
National Herring gull, great black-backed gull, common guillemot, razorbill
Regional Fulmar, gannet, common gull, kittiwake
Local None
11.5 Assessment of Impacts - Worst Case Scenario
11.5.1 As described in Section 11.3, this assessment focuses on the potential impact of the construction, operation and decommissioning of the GWF wind turbine array, inter-array cables and export cable on offshore ornithological receptors.
11.5.2 The assessment of direct and in-direct impacts associated with these offshore assets will focus on the issues identified in the NPS EN-3 (paragraph 2.6.101), as detailed in Section 11.2.4 above.
11.5.3 Identification of the worst case scenario for each receptor ensures that impacts of greater adverse significance would not arise should any other development scenario (as described in Chapter 5) to that assessed in this ES, be taken forward in the final scheme design. For the purpose of the offshore ornithology, the worst case scenario, taking into consideration these
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options, is detailed in Table 11.40. The worst case scenarios identified below are also applied to the assessment of cumulative impacts. In the event that the worst case scenarios for the project in isolation do not result in the worst case for cumulative impacts, this is addressed within the cumulative assessment section of the Chapter (see Section 11.10).
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Table 11.29 Realistic worst case scenarios for impacts on offshore ornithology
Impact Realistic Worst-case Scenario Justification
Construction
Direct disturbance and Maximum number of structures (140 WTGs, three met Provides for the largest possible noise over the greatest displacement from important masts, and four ancillary infrastructures) on 7m diameter spatial extent of the GWF site, over the largest temporal foraging and habitat areas monopiles. scale (piling over 39 months, within a total construction arising from underwater noise window of 56 months), with maximum level of concurrent Up to two piles installed at any one time (taking an indicative (for example, pile driving activity accounted for. 4 hours to install), with piling taking place over a operations for turbine and met construction window of 56 months. Piling is restricted to a Piling is considered to create the greatest potential for noise mast foundations). maximum of 39 months within this window and will not occur impacts upon birds during construction. 7m piles represent over more than two herring (November to February inclusive) the largest foundation options which require piling and will and sole (February to May inclusive) spawning periods. This therefore be associated with the loudest noise. is based on construction commencing in Q2/Q3 2015. Monopiles will only be installed out to a depth of 45m below Structures located across all three Development Areas within CD. Modelling undertaken by Subacoustech (2011) of 3m 45m below Chart Datum (CD) water depths, so that two piles pin piles (used for space frame foundations) was undertaken would be installed simultaneously at the furthest distance to investigate if the installation of smaller piles in deeper from each other within the site boundary (as shown in the parts of the site (over 45m where monopiles would not be modelled positions from (Subacoustech, 2011) (Technical used) might produce a greater noise impact range than 7m Appendix 13.B). monopiles in shallower water (as noise travels further in deeper water). As detailed in Subacoustech (2011) (see Technical Appendix 13.B), the worse case scenario for
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Impact Realistic Worst-case Scenario Justification noise associated with piling is represented by the 7m pile as the noise associated with its installation extends the furthest even though it's use in the site is more constrained than space frame options.
Noise from concurrent piling installation could represent a larger area for disturbance/displacement of birds. The worst case would be that two of the piles located furthest from each other within the development area are installed at the same time, thus producing the largest area of noise impact and therefore displacement.
Peak activity levels during summer months when conditions are favourable may affect breeding populations from the Alde-Ore Estuary SPA, currently in unfavourable condition. This will impact on both adults and chicks, if food provision is affected.
Direct disturbance and The maximum number of WTGs (140), four ancillary Option provides for the largest possible source of direct displacement from increased infrastructure (comprising offshore substation(s), collection disturbance from noise, vessel movements and other human activities (for example, platform(s) and or accommodation platform) and three met construction related activity over the longest time period. vessel traffic, and human masts installed over a 56 month construction programme. The longer the timeframe of construction activities, the presence). greater the likelihood that individuals’ fitness will be reduced. Construction programme is all-year round, which will cover Worst case scenario would be consequential increases in
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Impact Realistic Worst-case Scenario Justification peak occurrences of each species on migration or over mortality on populations due to long periods of disturbance winter. (e.g. throughout breeding or overwintering period). Displacement into adjacent areas would put pressure on the Export cable installation via plough throughout export cable existing populations, particularly in designated sites, e.g. route (5m x 190km = 0.95km2) the red-throated diver Outer Thames SPA population. Cable installation via plough for inter and intra-array cables No scheduling to avoid periods of key sensitivity for (300km x 5m = 1.5km2) vulnerable species will increase likelihood of significant Work on the cable route within the Outer Thames SPA to effects. take place throughout winter, coinciding with peak densities Increased potential for interaction with Outer Thames SPA of red-throated diver population of red-throated diver, particularly during the post- breeding September-October moult (when the birds would be flightless) and during periods of highest winter densities.
Direct Habitat Loss (foraging and Habitat loss: The loss of subtidal habitat will result from the placement of loafing habitat) built structures (and associated scour protection material) on 101 * 45m Gravity base structure (GBS) foundations with the seabed. The worst case scenario is therefore, Indirect impacts due to loss of scour protection applied to 100% of all foundations represented by the largest footprint from the foundation benthic prey resource and (160,590m2 + 174,730m2 = 335,320m2 (0.335km2)) structures (and associated scour protection) under changes to benthic habitat due to Three met mast foundations on 45m GBS foundations consideration. specific construction activities including 100% scour protection (4,770m2 + 5,190m2 = (for example, pile driving The GBS foundations have a larger footprint than any of the 9,960m2 (0.01km2)) operations for installation of foundations under consideration. Of the GBS options for the Up to four ancillary structures (this may comprise a
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Impact Realistic Worst-case Scenario Justification turbine monopiles, Met masts combination of offshore substation platforms (OSPs), WTGs, there could be up to 101 45m base diameter and offshore substations collection platforms and / or accommodation platforms) on structures or 140 35m base diameter structures. Scour (including scour protection). space frame (self-jacking suction can) foundations (four leg protection for 45m base diameter structures is 10m in radius Installation of gravity based jackets) assuming 100% scour protection = 18,748m2 around all structures and 9m around all structures for the structures and offshore cable (0.019km2)) 35m base diameter option. Therefore, the total footprint for assets (including scour the 45m base diameter option is 335,320m2, whilst for the Rock placement for cable protection at a total of 9 export protection). 35m option it is 308,856m2. The 101 45m base diameter cable crossings (3,240m2) option therefore, has the largest overall footprint. Total area = 0.335 + 0.01 + 0.019 + 0.003 = 0.37km2 For the met masts GBS options are considered and Disturbance of prey species from underwater noise: therefore, the 45m base diameter option presents the worst Maximum number of structures (140 WTGs, three met case. masts, and four ancillary infrastructures) on 7m diameter For the ancillary structures, only space frame (piled, suction monopiles . can and self-jacking) and monopile foundations are Up to two piles installed at any one time (taking an indicative considered. 4 hours to install). The area for a single self-jacking (suction can) space frame Structures located across all three Development Areas within foundation (based on up to four legs) with 100% scour 45m below Chart Datum (CD) water depths, so that two piles protection is 4,687m2. For the four foundations this equates would be installed simultaneously at the furthest distance to a total area of 18,748m2. from each other within the site boundary (as shown in the The area for a single (piled) space frame foundation (based modelled positions from (Subacoustech, 2011) (Technical on up to six legs (3m diameter) each with up to two (3m Appendix 13.B). 2 diameter) pin piles) is 85m . The piled space frame requires
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Impact Realistic Worst-case Scenario Justification 100% scour protection (with an additional 5m radius around each structure) the area of scour protection for four space frame structures is therefore 9,388m2.
A 7m monopile has a footprint of 38.5m2 with a scour protection footprint of 1,700m2 and therefore an overall footprint of 1,739m2 (total area of 6,956 m2 for four foundations) .
All other foundation types considered (Chapter 5) would result in a smaller loss of habitat.
The worst case scenario for disturbance to prey species (principally fish and cephalopods) represented by the 7m monopile and detailed in Table 13.9 in Chapter 13 and aligned with that justified for bird disturbance above.
Provides for the maximum number and intensity of potential sources of underwater noise.
Displacement resulting in The maximum number of WTGs (140), four ancillary Provides for the maximum amount (spatial extent) of habitat effective habitat loss from an infrastructure (comprising offshore substation(s), collection loss due to displacement effects, without allowing access to area around turbines and other platform(s) and or accommodation platform) and three met some parts of the turbine areas. For sensitive species (e.g. ancillary structures during the masts. red-throated diver, gannet), the wind farm as a whole will be operational phase of the avoided up to approximately 4km, whereas for others (e.g. WTGs to be spaced regularly within the turbine areas, up to
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Impact Realistic Worst-case Scenario Justification development. the site boundary, with no obvious corridors of access within. gulls), individual turbines will be avoided while within the wind farm, thereby increasing energy expenditure and reducing fitness.
Operation
Mortality as a result of direct 140 WTGs with a rotor diameter of 120m and a minimum The worst case scenario is established through the option collision with WTGs and other lower rotor tip clearance of 22m above MHWS. Two that provides that maximum ‘swept area’. ancillary structures offshore substations, one accommodation platform, one The adjacent worst case scenario provides the maximum collection platform and three met masts. number of structures in the wind farm, combined with the WTGs distributed evenly between Development Areas A, B rotor diameter that results in a greater rotor swept area to and C wind farm area ratio (i.e. the maximum swept area). The rotor-swept area was calculated by multiplying the area of one rotor (πr2) by the total number of WTGs (140) to give 1.58km2. Although other turbine types may have a larger rotor diameter, significantly fewer would be required, thereby reducing overall rotor swept area. Rotation period of smaller turbines is faster, thereby increasing collision risk.
Turbines provide lowest rotor tip height above MHWS which results in inclusion of flights at 20-30m height band, which are numerous compared to those at higher altitudes. Preparatory CRM conducted using alternative turbine types
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Impact Realistic Worst-case Scenario Justification showed that those with lower rotor tip heights at 30m+ had significantly lower mortality rates for all species.
CRM of lesser black-backed gull showed that locating more turbines in areas of lower densities recorded during baseline surveys decreased overall mortality rates. Differences were however minimal, although may be significant for other species with stronger patterns of distribution.
Barrier effects 140 WTGs with a rotor diameter of 120m and a minimum Provides the maximum number of structures in the wind lower rotor tip clearance of 22m above MHWS., three met farm, to increase likelihood that birds will avoid individual masts and four ancillary structures (two offshore substations, turbines or the wind farm as a whole. Impact assessment one accommodation platform and one collection platform). assumes that the turbines are spread out spatially to the boundary edge of each turbine array so that the maximum WTGs distributed evenly between Development Areas A, B overall area of sea is protected by a potential barrier of and C turbines, thereby maximizing the foraging area made unavailable to sensitive species.
Turbine type with lower rotor tip height closest to sea level will prohibit many birds from passing beneath turbine rotors.
Attraction to lit structures 140 WTGs, two offshore substations, one accommodation Provides the maximum number of structures in the wind platform, one collection platform and three met masts. farm, to increase likelihood that birds will be attracted to structures and become disoriented or more susceptible to Structures to be fitted with full lighting requirements for
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Impact Realistic Worst-case Scenario Justification aviation and shipping (see Chapters 16 Shipping and collision risk. Navigation and 17 Military and Civil Aviation)
Disturbance as a result of Daily activity within the wind farm area, export cable area Option provides for the largest possible source of direct activities associated with and vessel movements to and from the shore. Up to four or disturbance from noise, vessel movements and other maintenance of operational five small operations vessels would be running each day construction related activity over the longest time period. turbines, cables and other during the operational period. The longer the timeframe of construction activities, the infrastructure Concurrent maintenance activity from all vessels spread greater the likelihood that individuals’ fitness will be reduced. across the turbine areas Displacement into adjacent areas would put pressure on the existing populations.
Increased likelihood of significant impacts on Outer Thames SPA population of wintering red-throated diver, particularly due to vessel movements through SPA to wind farm, and also work on export cable route if required.
Decommissioning
Direct disturbance and Removal of all cabling and build structures (based on worst Arrangements associated with decommissioning will be displacement from increased case assumptions detailed under construction). determined prior to construction and a full Decommissioning human activities (for example, Plan for the project will be drawn up and agreed with DECC. vessel traffic, and human Until the arrangements have been clarified, the worst case presence). scenario is that all structures will be removed.
Direct Habitat Loss (foraging and Removal of all cabling and build structures (based on worst Arrangements associated with decommissioning will be
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Impact Realistic Worst-case Scenario Justification loafing habitat) case assumptions detailed under construction). determined prior to construction and a full Decommissioning Plan for the project will be drawn up and agreed with DECC. Indirect impacts due to loss of Until the arrangements have been clarified, the worst case benthic prey resource and scenario is that all structures will be removed. changes to benthic habitat.
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11.5.4 At this stage of the project it is difficult to assess the likely range of worst case decommissioning scenarios. The type of potential disturbance effects associated with decommissioning are likely to be similar to those identified for construction and therefore same worst case scenario is applied. This assumes that there is no permanent displacement of birds from the wind farm due to disturbance effects during construction.
11.5.5 Confidence from the significance results in the impact assessment of construction effects being applicable to decommissioning effects is, however, lower, as it is more difficult to determine levels of activity and population sizes of species over a long-term period (up to 25 years in advance).
11.6 Assessment of Impacts during the Construction Phase
11.6.1 This section provides an assessment of the potential impacts from the construction phase of the GWF project on offshore ornithology. Potential construction impacts highlighted by the NPS EN-3, identified during the Scoping process and through consultation with the SNCAs and RSPB, Table 11.2, are associated with:
Habitat loss (long-term physical loss of habitat due to construction of infrastructure resulting a direct impact to a species); Direct disturbance and displacement from construction activity (for example, an increase in vessel activity, human presence and pile driving activities), amounting to habitat loss for the period of disturbance; and In-direct disturbance effects through changes to prey supply from construction activities and increased vessel traffic.
Habitat loss 11.6.2 Direct habitat loss may result in loss or fragmentation of foraging or loafing habitat for particular species. For wind farm developments, this is generally relatively small, amounting to the area lost to turbine bases and associated infrastructure; typically <1% of the total development footprint (Drewitt and Langston, 2006). With respect to seabirds, this physical loss is likely to be considerably less than any effective habitat loss due to indirect disturbance or displacement from the wind farm area. Effects may be more widespread however, if developments interfere with the turbidity or quality of the surrounding area of sea. This indirect (secondary) impact of habitat loss may occur if habitats associated with prey species are removed, which would result in the loss of a food resource to birds in the wind farm area.
11.6.3 The vulnerability of species to direct habitat loss depends on their flexibility, based on their specific habitat requirements. This is assessed using the species general sensitivity to habitat loss summarised in Table 11.6 from Garthe and Hüppop’s (2004) scoring system, and expert judgement based on literature available from other operational wind farm sites. The GWF
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site-specific sensitivity for habitat loss is considered to be Very High for red- throated diver, Medium for Arctic skua, great skua, lesser black-backed gull, herring gull, great-black-backed gull, common guillemot and razorbill, and Low for gannet, fulmar, kittiwake and common gull.
11.6.4 In the ‘worst-case’ scenario layout, Table 11.29, maximum habitat loss will be the total area of 101 turbine bases using 45m gravity base structure (GBS) foundations (160,590m2), plus other ancillary structures, cable protection and associated scour protection, to give a total of 0.37km2. The total area affected will constitute 0.17% of the total consent area (222km2). The majority of seabed lost will be as a result of the WTG foundations and associated scour protection.
11.6.5 There are likely to be some changes in sediment and habitat type immediately adjacent to the subsea portion of these structures, which may affect the benthic fauna and prey species locally. As the area lost is likely to be less than 1% of the total wind farm area, any such loss of foraging or loafing habitat is considered to be of negligible magnitude for any species of principle concern.
11.6.6 This results in a predicted impact of Negligible significance for Arctic skua, great skua, lesser black-backed gull, herring gull, great-black- backed gull, common guillemot, razorbill, gannet, fulmar, kittiwake and common gull.
11.6.7 Based on the ‘very high’ site-specific sensitivity of red-throated diver to habitat loss, this species may encounter a Minor adverse impact on the wintering regional population. The export cable route will pass through the Outer Thames SPA, however, the cable is likely to be ploughed or jetted into the seabed which would suggest that no long-term habitat loss is likely to occur for red-throated diver which utilise seabed habitat within the GWF footprint. There will be no significant impact on the Outer Thames SPA population.
Table 11.30 Predicted significance of habitat loss on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible All levels Negligible skua
Common National Low Medium Negligible All levels Negligible guillemot
Common Regional Low Low Negligible All levels Negligible gull
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Fulmar Regional Very Low Low Negligible All levels Negligible
Gannet Regional Very Low Low Negligible All levels Negligible
Great National Low Medium Negligible All levels Negligible black- backed gull
Great International Very Low Medium Negligible All levels Negligible skua
Herring National Low Medium Negligible All levels Negligible gull
Kittiwake Regional Low Low Negligible All levels Negligible
Lesser International Low Medium Negligible All levels Negligible black- backed gull
Razorbill National Low Medium Negligible All levels Negligible
Red- International High Very High Negligible Regional/ Minor throated SPA adverse/ not diver significant effect
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Direct disturbance and displacement from construction activity 11.6.8 Disturbance during the construction of a wind farm (visual presence, vessel activity and underwater noise, as per Drewitt and Langston 2006) may displace birds from an area of sea, effectively amounting to habitat loss for the period of disturbance. Disturbance caused by construction activities may directly displace birds from foraging or loafing areas (although the actual habitat quality remains otherwise the same in the long term) thus potentially affecting breeding success or survival.
11.6.9 As per Maclean et al. (2009), it is initially assumed that all birds are displaced from the GWF study area due to disturbance, in order to determine the maximum magnitude of impact. This involves assessing the
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displacement of peak densities in the context of relevant SPA, regional, national and/or international populations.
11.6.10 The impacts are initially considered up to what is likely to be a very precautionary 4km buffer, as recommended by Maclean et al. (2009), based on evidence that scoters and auks have shown evidence of avoidance up to this distance at the Horns Rev Wind Farm in Denmark (Petersen 2004, 2005). This buffer is reduced further for all species where empirical evidence and/or expert judgment suggests that impacts are limited to within the 1km buffer and/or immediate wind farm footprint. In practice, it is likely that many species, in particular gulls, will be able to tolerate human disturbance at a much smaller distance (e.g. Petersen et al. 2006; Krijgsveld et al. 2010; Leopold et al. 2010) and that, as time passes, some species may be able to habituate to regular disturbance sources, thereby decreasing the magnitude and extent of effect over time.
11.6.11 For each of the species of principal concern, the increase in visual and noise disturbance associated with human construction activities has been evaluated using the following information:
Evaluation of species’ sensitivity to disturbance by ship and helicopter traffic, and habitat use flexibility in Garthe and Hüppop (2004); Evaluation of species’ sensitivity to disturbance and flexibility of habitat usage in Maclean et al. (2009); Evidence of species’ sensitivity to construction activity from the scientific literature (e.g. Leopold and Camphuysen, 2007); and The level of site usage in the GWF study area, for example feeding activity records and period of occurrence (e.g. annual, overwintering, migratory).
11.6.12 In general, it was considered that effects are likely to last only for the duration of construction activity and, therefore, will be direct, but temporary, reversible and short-term in nature. The spatial extent of construction- related disturbance is also likely to be less than the recommended entire buffer out to 4km from GWF turbine areas for the majority of species, although the exact level may differ per species or per construction activity.
11.6.13 The worst-case scenario, Table 11.29, presents the construction of the maximum number of WTGs (140), four ancillary infrastructure components (comprising offshore substation(s), collection platform(s) and/or accommodation platform) and three met masts, all piled over a period of 39 months from April 2015, within a total construction window of 56 months.
11.6.14 Up to two piling vessels and rigs may be present during construction at the GWF site at any one time. A worst case scenario would involve two piles being installed simultaneously at the furthest distance from each other
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within the site boundary- thus providing the maximum footprint for vessel transit activity and underwater noise disturbance.
Disturbance from underwater noise (from pile driving and vessel activity) 11.6.15 The largest potential impacts in relation to displacement from underwater noise are associated with irregular but intensive pile-driving activities, which can give rise to injurious or disturbing sound fields. A more detailed assessment of the in-direct effects of underwater noise on prey species is provided in Section 4.95 of Technical Appendix 11.A.
11.6.16 Seabird species most vulnerable to direct disturbance from anthropogenic underwater noise are those which forage underwater hunting for prey (such as fish and shellfish)- notably auks, divers and seaduck. Gull species feed at the surface and are therefore considered less vulnerable (Leopold and Camphuysen, 2007).
11.6.17 Although effects of underwater noise associated with pile-driving activity are well-studied for marine mammals and fish (e.g. Madsen et al. 2006), very little is known about the effects on seabirds. Studies by Turnpenny and Nedwell (1994) suggest that state that “From the limited work on seabirds and seismic surveys (undertaken in Canada), no evidence was found of harm caused by the use of air guns, and even chemical explosives were rarely harmful unless the birds ventured very close to detonations”.
11.6.18 The only available data related to the effects of impulsive underwater noise on marine birds was published by Yelverton et al. (1973), as part of their assessment of mortality and injury criteria for submerged birds from the shock waves from high explosives. There are no data on impact thresholds for marine birds exposed to continuous noise (JASCO, 2009), therefore vessel noise impacts on marine avifauna are difficult to determine.
11.6.19 Visual observations by Leopold and Camphuysen (2007) before and during three pile driving sessions at the Egmond aan Zee OWF in the Netherlands did not detect any of the seabirds deemed sensitive to pile driving noise in the vicinity of the construction work, as divers, auks and seaducks would largely have migrated from the area by the commencement date. However, birds that did fly by the construction site (mainly gulls and terns) did not show a noticeable reaction to the activities. It is therefore likely at the GWF that the many of the most numerous species that were present (e.g. gulls, fulmar) are least likely to be affected by construction disturbance due to pile-driving, although it is possible that auks and divers may show a localised response.
Disturbance from vessel activity (including airborne noise) and human presence 11.6.20 The presence of plant and personnel at the GWF site may also cause localised disturbance throughout construction. In all cases, such
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disturbance impacts are likely to be temporary and exist only when vessels are on site and / or particular construction activities are being undertaken.
11.6.21 Birds may readily re-distribute in periods of less intense or no activity during the construction period.
Red-throated diver- offshore wind turbine array 11.6.22 Garthe and Hüppop (2004) rate red-throated diver as being of the highest sensitivity to boat-based disturbance. Their general sensitivity to disturbance was considered by Maclean et al. (2009) to be ‘Very High’. It was evident from the GWF boat-based surveys that red-throated diver were affected by the presence of vessels, with the majority of records indicating that birds were fleeing the vicinity in response to the survey vessel’s movements. Due to its International conservation value, the site-specific sensitivity of red-throated diver to construction disturbance from the GWF is rated as ‘Very High’.
11.6.23 Red-throated divers are likely to be most sensitive to disturbance between mid-September and December when birds are moulting and cannot fly off in response to boat traffic. Within the GWF survey area, numbers were low during this period (a peak of 24 birds was observed in early January 2009). Numbers in the GWF survey area exceeded national importance in February 2009 with 123 individuals (peak estimate of 43-204), Table 11.27. Numbers also appeared to have exceeded regional thresholds within the smaller ‘GWF study area’ in the following month (peak estimate of 112). This March peak represents 1.4% of the regional wintering population and 1.7% of the Outer Thames SPA population.
11.6.24 Construction activity is likely to be less intensive during the winter months, due to adverse weather conditions and, therefore, will reduce the likelihood of impacts occurring during the period of highest diver activity. It should be noted that GWF construction activities are likely to be concentrated around one or two turbines per day (GGOWF: Table 11.4). Therefore, any disturbance is likely to be localised in nature and occur over the short-term, thus removing any additive effects over the lifespan of the wind farm. The peak population estimates for the immediate GWF footprint (Area A, B and C combined) were 81 individuals (regionally important) and 22 individuals, for March 2009 and February 2010 respectively. With localised impacts occurring at up to two turbines at a time, the temporary displacement of a low number of red-throated diver from the GWF footprint will likely create a Minor adverse impact on the regional population and a Non-significant impact on the SPA population (see Section 11.3.60 and the HRA Report).
Red-throated diver- export cable 11.6.25 The planned routes of the export cables pass through the Outer Thames SPA from the GWF to the Suffolk coast. This may create a localised source of disturbance to red-throated diver along the construction area for the
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export cable route (up to 0.75km2 within the export corridor, the remaining 0.2km2 occurring within the wind farm array extent). Temporary displacement is likely to be limited to an area immediately adjacent to the cable laying activities (which is likely to constitute up to two vessels). Even if a precautionary disturbance buffer of 2km were assumed around the cable route area, this is equivalent to 0.3% of the total area of the Outer Thames SPA (3,793km2). Furthermore, the majority of the export cable is at depths in excess of 20m (Figure 11.5), which is widely considered to be sub-optimal for red-throated diver (DTI, 2006; BERR, 2007; RPS, 2005).
11.6.26 The SPA area is currently used intensively by various vessel types, and despite this, numbers of red-throated diver recorded during aerial surveys within the Thames Strategic Area appear to be stable. Tables 21 and 22a, Technical Appendix 11.A suggest that sector TH4, where much of the GWF cable route would be located, is not as important for red-throated diver as the adjacent TH1 sector (although probably more so than TH3).
11.6.27 Any disturbance associated with the cable installation work would be short- term in nature and set in context of an area of sea regularly used by a number of different marine vessels (see Section 16.4 of Chapter 16). Consequently it is considered that there will be a Minor adverse impact on the regional population and a Non-significant impact on the SPA population, (see Section 11.3.60 and the HRA Report).
Lesser black-backed gull 11.6.28 It was evident from GWF boat-based surveys that, even at close proximity, most gull species remained undisturbed by the presence of vessel traffic. This is likely a reflection of these birds’ behavioural flexibility with regards to foraging strategies, which often includes exploiting discards from fishing vessels. Garthe and Hüppop (2004) rated lesser black-backed gull as being of low sensitivity to boat-based disturbance, and the general sensitivity of the species to disturbance was considered to be ‘Low’. Due to its inclusion in the Alde-Ore Estuary SPA (International conservation value), however, the GWF site-specific sensitivity of lesser black-backed gull to construction disturbance is elevated to ‘High’.
11.6.29 Within the GWF survey area, numbers exceeded national importance in four months in each survey year – June/July, December, February and March, with a peak count of 2,794 birds within the GWF study area in early January 2009, Table 11.25. This apparent peak represented nearly 10% of the regional wintering population, and 1.2% of the national winter population. In June, the average GWF study area population of 2,215 (1,811-2,618) individuals reached 31% of the regional breeding population and 69% of the current SPA breeding population.
11.6.30 It is evident from the sightings records of the GWF boat surveys and the wider literature (for example, Schwemmer and Garthe, 2005; Leopold et al. 2010), that lesser black-backed gull are unlikely to be negatively affected by the presence of human-related activities. Despite noisy works, machinery
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operations and human presence, many species of gull are known to colonise industrial sites across the UK, for example at landfill sites. Visual observations by Leopold and Camphuysen (2007) before and during three pile driving sessions at the Egmond aan Zee (OWEZ) Wind Farm in the Netherlands did not detect any noticeable reactions of gulls to construction activities. In this instance, the 4km disturbance buffer recommended by Maclean et al. (2009) appears over-precautionary in the case of some gull species, and even using the GWF study area population estimates is likely to be a large overestimate of disturbance impacts.
11.6.31 Due to the species’ tolerance of human activities and the presence of alternative foraging habitat available within the GWF and surrounding area (Section 4.109, Technical Appendix 11.A), it is predicted that any unlikely temporary displacement of lesser black-backed gull from a localised area will have no observable impact on an individual’s fitness or breeding success. The lesser black-backed gull’s long reproductive lifespan means that long-term impacts are unlikely. Populations are likely to comprise a sizeable proportion of non-breeders and birds from outside the regional and SPA populations, either on migration or foraging widely from colonies elsewhere in the south-east region or from the large colonies across the Netherland’s coast. It is, therefore, considered that disturbance will create, at worst, a Low magnitude effect and temporary, reversible Minor adverse impact on the regional and SPA populations at any scale, and a Non- significant adverse impact (<1%) on the Alde-Ore Estuary SPA population, (see Section 11.3.60 and the HRA Report).
Great black-backed gull 11.6.32 The GWF site-specific sensitivity of great black-backed gull is considered to be Medium, as the species is of National conservation status, with a low general sensitivity to disturbance Table 11.6.
11.6.33 Great black-backed gull was recorded in nationally-important numbers in early January 2009, peaking at 436 birds in the GWF wind farm (Areas A, B and C combined), Table 11.21, which is just over the national winter threshold and 1.7% of the wintering regional population. A loss of these birds would result in a low impact magnitude on the national and regional winter populations. As with lesser black-backed gull, it is likely that great black-backed gull will be undisturbed by temporary, localised increases in machinery operation, vessel traffic and human presence. As with lesser black-backed gull, it is likely that great black-backed gull will be undisturbed by construction activities and so a reversible Minor adverse impact on the regional population over the short-term period of construction is seen as a precautionary assessment.
Herring gull 11.6.34 The GWF site-specific sensitivity level of herring gull is considered to be Medium. The species has a National conservation status in this context, despite low general sensitivity to disturbance Table 11.6.
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11.6.35 Herring gull was recorded in peak numbers in the GWF study area during early January 2009, with 262 individuals within the GWF footprint, with 0.4% of the regional wintering population. In summer, numbers peaked to 10 (0- 18) birds in July, which was 0.4% of the regional summer population, and 0.7% of the estimated Alde-Ore Estuary SPA assemblage population (taken to be 672 pairs, from 2010 counts by Landguard Bird Observatory and RSPB). Over the temporary construction period, a loss of these birds would therefore be of a Negligible impact magnitude to the regional and SPA populations. As with other gulls, it is likely that herring gull will be undisturbed by construction activities, leading to a Minor adverse impact on the regional population. GPS data from RSPB tagging surveys during summer 2011 of eight Alde-Ore Estuary SPA breeding herring gull has shown that the site is likely to be beyond regular foraging range of this coastal population, with foraging trips restricted to the coast and inland, resulting in a non-significant adverse impact on the Alde Ore SPA population, (see Section 11.3.60).
Kittiwake 11.6.36 Kittiwake is a receptor of Regional conservation value, and is rated as being of Low general sensitivity to disturbance (Leopold and Camphuysen 2007, Maclean et al. 2009 and Garthe and Hüppop 2004). This results in a ‘Low’ GWF site-specific sensitivity to disturbance.
11.6.37 Numbers of kittiwake peaked within the GWF footprint in March 2009, reaching 178 individuals, or 0.6% of the regional winter population. With the highly precautionary assumption that these animals would be lost from the winter regional population, the magnitude of such an impact would be negligible.. Similarly, if the estimated summer peak of 84 individuals within the GWF footprint were lost from the summer breeding population (360 pairs), this would result in a Medium impact magnitude. This value is, however, considered very unlikely to represent up to 11% of the regional breeding population, with most birds recorded likely to be on migration to the large breeding colonies in the north of Europe, and part of the wintering population of over 30,000 individuals, or the larger flyway population of 8.4 million birds (Stienen et al. 2007). Figures 84 and 85, Technical Appendix 11.A suggest that in April, around 20% of birds identified were immature and therefore not part of the breeding population. Temporary disturbance would therefore likely result in at worst, a reversible Minor adverse impact on the regional breeding population.
Common gull 11.6.38 Being of Regional conservation value, the common gull has a ‘Low’ GWF site-specific sensitivity to disturbance. Numbers were generally low throughout the year, particularly in the GWF study area, which reflects the mostly coastal distribution of the species. Estimated populations within the GWF study area did not reach the 1% regional population threshold in summer or winter, and therefore any disturbance effects were considered to
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be of Negligible magnitude, and resulted in a likely Negligible adverse impact on the regional population.
Gannet 11.6.39 The peak gannet (Regional conservation value) population in the GWF footprint occurred in early November 2008, where 226 individuals equated to 2.7% of the winter regional population, Table 11.20. Under the precautionary assumption that these gannet (which are considered to have a low sensitivity to direct disturbance and displacement, Table 11.6) would be temporarily displaced from the wind farm footprint, this would result in a Low impact magnitude and Negligible impact on the regional winter population. Furthermore, gannet are a wide-ranging forager that are likely to tolerate any temporary losses in a small part of its foraging range. In summer, numbers within the GWF footprint are lower, with a peak of 225 individuals in April 2010. This low impact magnitude would result in an overall Negligible impact on the regional breeding population.
Northern fulmar 11.6.40 The estimated GWF fulmar population reached a peak of 448 individuals in January 2010 (which equates to 16.7% of the regional resident population), Table 11.19. Fulmar are considered to have a very low general sensitivity to direct disturbance (Table 11.6), combined with their Regional conservation value is predicted that fulmar have a low site-specific sensitivity to disturbance. Assuming these birds were temporarily displaced from the wind farm footprint, a medium impact magnitude at this scale would result in a temporary, reversible Minor adverse impact on the regional winter population. This worst case is considered to be an overestimate of the realistic impact magnitude, since the winter numbers are likely to be much greater, considering the flyway population of 10 million individuals (Stienen et al. 2007).
Skua 11.6.41 Arctic skua and great skua were recorded on passage within the GWF study area, almost exclusively during August and September, Table 11.16 and Table 11.22. Theoretically, based on their International conservation status and general sensitivity to disturbance ‘Very Low’ (Garthe and Hüppop. 2004) and Maclean et al. (2009), plus evidence from other wind farm sites (Krijgsveld et al. 2010) - their GWF site-specific sensitivity to disturbance is predicted to be Low.
11.6.42 Although it is acknowledged that peak passage numbers of these species may have been missed by boat-based surveys, construction activities are not likely to have a significant impact on migrating birds, with their usage of the GWF site being minimal.
11.6.43 Arctic skua were not recorded in national or regionally-important numbers during the migration period (peak estimate of 28 birds in the whole GWF survey area in August 2008) and due to the site’s limited importance for the
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species, any localised construction activity for birds passing though on migration is likely to be of Negligible magnitude, which represents a Negligible impact on the national and passage populations, and on any SPA population where the species is a qualifier during the breeding season, or on passage, (see Section 11.3.60).
11.6.44 Great skua numbers apparently peaked at an average estimate of 139 (37- 241) individuals within the GWF study area in September 2008, which represents 0.7% of the national breeding population and 0.5% of the migratory population. The migratory population is considered to be the most appropriate reference population since individuals within the GWF survey area were recorded during passage periods only. This would theoretically result in a Negligible magnitude effect on the national breeding population and the migratory population. No SPAs where the species is a qualifier (either breeding or staging) would be significantly affected based on these numbers relative to the migratory population, see Section 11.3.60. This would equate to, at worst, a temporary, reversible Minor adverse impact on the national and migratory populations and a non-significant effect on any SPA population over the period of construction (Appendix D of the HRA Report).
Auks 11.6.45 Common guillemot and razorbill are considered to have a Medium general sensitivity to disturbance (Garthe and Hüppop, 2004; Maclean et al. 2009). Which suggests any potential construction disturbance at GWF may affect both species to some extent. Both species approached nationally-important numbers in the wider survey area and so are of High conservation sensitivity. This results in common guillemot and razorbill having a ‘High’ site-specific sensitivity to disturbance.
11.6.46 Very large numbers of auks were recorded during aerial surveys of the Greater Gabbard block in February 2008 (a population estimate of 18,141 individuals), and assuming the large majority were common guillemots, numbers approached 1% of the national breeding common guillemot population (1.3 million individuals) and around 50-60% of the regional winter population (29,291 individuals).
11.6.47 The aerial survey area was however much larger than the GWF study area (Areas A, B, C and 1-4km buffer combined) and so numbers (average peak of 3,219 individuals in February, which equals 0.2% of national, and 11.0% of regional populations) are more likely to show lower magnitudes of effect on the national and regional populations during the construction period. Although overwintering auks may theoretically be susceptible to the short- term disturbance caused by cable-laying activities, the bulk of this activity will likely take place closer to the shoreline than preferred by common guillemot and razorbill during this period, as seen in aerial surveys of the Thames Strategic Area (Section 11.4). Such activities are unlikely to
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significantly interfere with foraging abilities and impact on individuals’ fitness over a long-term period.
11.6.48 Results from aerial surveys showed that common guillemot is distributed widely in the Greater Thames during winter, although there were generally larger concentrations further offshore. During boat-based surveys only 1.5% of common guillemots were recorded feeding in the GWF survey area, although it is acknowledged that this behaviour will be under-recorded due to both species’ propensity to dive below the surface if disturbed by the survey vessel. Nevertheless, the GWF study area does not appear to be particularly important for the species, with high numbers of common guillemot recorded in February 2008 during aerial surveys in the wider Greater Gabbard survey block, and February 2009 during boat-based surveys in the GWF survey area. The significance is considered a short- term, tolerable Moderate adverse impact on the regional wintering common guillemot population and a Negligible impact on the national wintering population during the construction period.
11.6.49 Razorbill reached a peak of 1,007 (313-1,701) birds in the GWF study area in February, which was considered to be around 16.3% of the regional wintering population and 0.6% of the national population. The GWF area does not appear to be important for the species within the context of the South and East North Sea or Greater Thames Strategic Area (Figure 101, Technical Appendix 11.A). As a wide ranging forager, in winter months at least, it is likely that alternative habitat would be readily available during the construction period, allowing these auks to track prey movements away from localised point sources of disturbance. Resulting in a short-term, tolerable Moderate adverse impact on the wintering regional population and a Negligible impact on the national population over the period of construction.
11.6.50 A summary of predicted significance of effects is presented below in Table 11.31.
Table 11.31 Predicted significance of direct disturbance on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible Migratory Negligible and SPA skua
Common National Medium High Medium Regional Moderate but winter and tolerable / guillemot National Negligible Common Regional Low Low Negligible Regional Negligible
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude gull
Fulmar Regional Very Low Low High Regional Minor winter Gannet Regional Low Low Minor Regional Negligible winter and breeding Great National Low Medium Minor Regional Minor black- backed gull
Great International Very Low Medium Negligible Migratory Negligible and SPA skua
Herring National Low Medium Minor Regional Minor / Not breeding and significant gull SPA Kittiwake Regional Low Low High Regional Minor breeding Lesser International Low High High Regional Minor / Not breeding and significant black- SPA backed gull
Razorbill National Medium High Medium Regional Moderate but winter and tolerable / National Negligible Red- International Very High Very High Low Regional Minor / Not winter and significant throated SPA diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
In-direct impacts from construction activity
11.6.51 The indirect effects on prey resource and habitats is detailed in Chapters 9 (Section 9.6), 12 (Section 12.6) and 13 (Section 13.6) of this ES. Principal impacts on these resources and habitats manifests as a result of construction noise and physical disturbance experienced during foundation and cable installation.
11.6.52 For each of the species of principal concern, the indirect disturbance due to adverse effects on important prey species and habitats has been evaluated
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against the worst-case scenario, Table 11.29, using the following information:
Evaluation of species’ sensitivity to flexibility of habitat usage in Garthe and Huppop (2004) and Maclean et al. (2009); Ecology and behaviour of species, e.g. in obtaining food, from the scientific literature and boat-based surveys; The level of site usage in the GWF study area, for example feeding activity records and period of occurrence (e.g. annual, overwintering, migratory); and Results from the assessment of the effects on benthos and fish in other ES chapters.
11.6.53 Similar to direct disturbance described above, the worst-case scenario outlined in Table 11.29 will likely consist of the maximum number of structures (140 turbines, three met masts, and four ancillary infrastructures) on 7.0m diameter monopiles. Up to two piles would be installed at any one time (taking an indicative 4 hours to install) at the furthest distance from each other within the site boundary, resulting in the most extensive area of potential disturbance to prey species.
11.6.54 There have been a variety of assessments of the potential behavioural and physiological effects of pile-driving noise on a range of fish species, Section 4.131-4133 Technical Appendix 11.A, and the possible ecological consequences of the loss or displacement of important prey species on seabird populations, Section 4.135-4.136 Technical Appendix 11.A.
11.6.55 At GWF, the main construction activities with the potential to have a significant impact on fish are associated with the installation of 7.0m diameter monopiles via impact piling. As detailed in Chapter 5 Project Details the installation of the offshore elements is likely to take place primarily outside of the winter months (i.e. carried out in March to November) due to the potential adverse weather conditions leading to delays in activities and excessive costs. Chapter 13: Natural Fish and Shellfish Resource concluded that the GWF project is predicted unlikely to have population-level effects on any prey stock. Piling operations are intermittent; any localised displacement of prey species would have a low impact magnitude over a short duration. It is anticipated that the overall effects on all seabirds of principle concern would be Negligible at all levels.
11.6.56 The physical disturbance of habitats (for fish), direct impacts on benthos and indirect impacts on habitats are all considered to be of Negligible significance given the relatively small area of disturbance in relation to the extent of the populations, communities and habitats present (see Sections 12.6 and 13.6 of Chapters 12 and 13, respectively).
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11.6.57 A sediment plume would likely be created during installation of turbine foundations and cable installation, although the concentrations would be low and within background concentrations and the plume only likely to extend over a small area (see Section 9.6 of Chapter 9). It was concluded that the effects of foundation construction at the GWF on sediment transport and morphology would be insignificant. The benthic communities of the Greater Thames are adapted to surviving in turbid waters with very high levels of suspended sediments (GGOWL, 2005) Chapter 12: Marine and Intertidal Ecology. As the benthos is generally tolerant of small, localised increases in suspended sediment, no significant impacts were predicted for the important benthic prey species for any species of principle concern, Table 11.32.
Table 11.32 Avian species of principal concern prey preferences in the offshore environment.
Species Food in marine environment Arctic skua Mainly fish obtained by piracy on auks, small gulls and terns
Common guillemot Herring, cod, capelin, sandeels
Common gull Fish (haddock, herring, blennies) and aquatic invertebrates (echinoderms, crustaceans, bivalves)
Fulmar Mainly crustaceans, cephalopods, fish, fish discards and carrion
Gannet Fish including herring, capelin, cod, whiting, haddock
Great black-backed gull Predation (terns), piracy and scavenging, fish (herring, mackerel, plaice, sandeels), crustaceans
Great skua Mainly fish obtained by piracy, also seabird predation
Herring gull Fish , fish discards, fish from piracy, invertebrates
Kittiwake Fish (sandeels, herring, cod), invertebrates and discards
Lesser black-backed gull Fish (cod, herring, flounders, sandeels), fish discards, fish from piracy, invertebrates
Razorbill Mainly sandeels with sprat and herring
Red-throated diver Mainly cod, herrings, sprats, followed by gobies, sticklebacks and sandeels
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11. Taken from the BWPi
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Red-throated diver- offshore wind turbine array 11.6.58 Red-throated diver feed largely on fish, and to a lesser extent molluscs and crustaceans, which is achieved by foot-propelled surface-diving up to 21m (Palmer, 1962; BWPi). Garthe and Huppop (2004) rate the species as being 4 out of 5 for inflexibility to habitat loss, and similarly, Maclean et al. (2009) rate the species as of High sensitivity. The GWF site-specific sensitivity is rated as Very High.
11.6.59 During the peak winter months, particularly February and March, red- throated diver are present in regionally-important numbers within the GWF study area (peak of 1.4% and 1.7% of the Outer Thames SPA population).
11.6.60 It is likely that peak numbers of birds during March consisted of a large number of birds passing on migration to breeding grounds further north, and therefore the GWF site is of possible importance for a brief period, largely for birds originating outside of the regional population. As such, there is unlikely to be more than a Negligible magnitude effect on the regional population, and therefore at worst a Minor adverse impact on the regional population which is short-term in nature and reversible, and a Non-significant adverse impact on the Outer Thames SPA population. Refer to the HRA Report for more details.
Red-throated diver- export cable 11.6.61 Similar to the reasons described above, the effect on red-throated diver prey items from subsea export cable installation will be of Negligible magnitude at a regional level and therefore again at worst a Minor adverse impact on the regional population, and a Non-significant adverse impact on the SPA population. Any effect on seabed habitat is likely to be of a much smaller intensity and extent compared to the dredging activity that currently takes place in the Thames area (DTI, 2006b)
Lesser black-backed gull 11.6.62 Lesser black-backed gull use various strategies to obtain food, including scavenging, kleptoparasitism, dip-diving, surface-plunging, and shallow plunge-diving for up to two seconds (BWPi). As a consequence, the species is rated as being most flexible in habitat use by Garthe and Hüppop (2004), and due to their wide-ranging nature, it is likely that birds will find alternative food resources in adjacent areas unaffected by disturbance. Although lesser black-backed gull may forage for fish within the GWF, which may be displaced by construction-related disturbance events, there is no evidence to indicate that these prey items will be consequently unavailable to birds, or that they will not return to the area once construction is complete over the short-term. It is predicted that, although the species is of Very High conservation status, the GWF site-specific sensitivity will be no more than Medium.
11.6.63 The conservation objectives of the SPA (JNCC/Natural England, 2010) highlight the wide variety of food sources potentially available to the colony.
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If prey species are temporarily unavailable, alternative choices are present. Results from tagged birds within the SPA (BTO and RSPB projects) both suggest that individual birds have various foraging strategies, both inland (at agricultural fields, piggeries and quarries) and offshore. Given the diversity of foraging opportunities, small-scale and temporary disturbance of offshore prey is likely to have a low impact magnitude. Resulting in no more than a Minor adverse impact on the regional population and a Non- significant on the SPA population. Refer to the HRA Report.
Other gulls 11.6.64 Other species of gull, including herring gull, great black-backed gull, common gull and kittiwake, are rated as being of Low sensitivity in their habitat requirements by Garthe and Hüppop (2004) and Maclean et al. (2009). This reflects their ability to forage widely on a variety of prey items, resulting in site-specific sensitivities of Medium for the former two, and Low for the latter two species. Gull foraging strategies mainly involve snatching food items from the surface or dipping just below the surface (BWPi; Ratcliffe et al., 2000), and so are unlikely to be affected by increases in water turbidity or temporary local prey losses.
11.6.65 For these gulls therefore, any temporary and local reductions in prey as a result of construction disturbance is not likely to constitute any more than a Low magnitude impact for any species. Resulting in no more than a Minor adverse impact on regional herring gull and great black-backed gull populations and a Negligible impact on regional kittiwake and common gull populations. There will be a Negligible impact on national populations, which for all four species, are large.
11.6.66 Although the herring gull Alde-Ore Estuary SPA population is in decline, no significant SPA impacts are predicted, for similar reasons to lesser black- backed gull described above. Herring gull is a more coastal forager (see Section 4 of Technical Appendix 11.A) and therefore the GWF site is likely to be of lesser significance to the species, with most individuals present during winter originating from other colonies across northern Europe.
Fulmar and gannet 11.6.67 Due to their wide ranging foraging behaviour and flexibility of foraging strategy (as recorded during boat-based surveys), both fulmar and gannet are considered to be of Very Low general sensitivity to indirect effects on prey.
11.6.68 Fulmars may dive further into the water column (with maximum recorded dive depths ranging from 3m (Garthe and Furness, 2001) to 4m (BWPi)), although since diving has been recorded at night (Furness and Todd, 1984), it is unlikely that the change in turbidity will prove to be a complete impediment. As a wide-ranging species of that has been known to travel up to 400km for food (Dunnet and Ollason, 1982), any temporary localised
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prey losses will be of Negligible magnitude on the species, which is of Low site-specific sensitivity. It is therefore predicted that there will be a Negligible impact on the regional and national populations.
11.6.69 From the literature, Gannet dive records range from a mean depth of 5m (maximum 22m) (Garthe et al., 2000) to 20m (maximum 34m) (Brierley and Fernandes, 2001). Dive depths tend to be deeper around midday and shallower around dawn and dusk (Garthe et al., 1999; Lewis et al., 2002), Section 4.155, Technical Appendix 11.A. Gannet forage primarily on lipid-rich pelagic fish up to 30cm in length such as herring, cod and sandeel (Hamer et al., 2000; BWPi), which are commonly found in the GWF area. The species is also known to forage extensively on fishery discards within the GWF study area. This scavenging behaviour was observed during boat-based surveys at GWF, and so it is unlikely that birds will be affected by temporary local losses in particular prey items. Gannet commonly forage within 100km of their breeding site (Tasker et al., 1985, Ratcliffe et al., 2000), although maximum foraging distances of 540km were recorded from the Bass Rock colony (Hamer et al., 2000). Boat-based survey data suggests that the GWF study area is relatively unimportant for gannet, the density and distribution of sightings are inconsistent- often associated with fishing activity. Any local reductions in prey availability within the footprint of the temporary disturbance to fish aggregations are likely to constitute no more than a Low magnitude impact for gannet, which is a species of Low site-specific sensitivity. This results in a Negligible impact on the national and regional populations, which are large.
Skua 11.6.70 Great skua and Arctic skua are present within the GWF study area only for short periods of time during the autumn migration, and so any construction effects would be limited to this period. Both species generally obtain food via kleptoparasitism although will occasionally take discards from fishing vessels. It is evident from the GWF boat-based data that the site is relatively unimportant for either species of skua and as such, any indirect effects of construction activity (which would be through effects on prey of other seabird species that would be kleptoparasitised) are considered to be of Negligible magnitude and therefore present no more than a Negligible impact on the migratory populations and a non- significant impact on any SPA population of either species. Refer to Appendix D of the HRA Report.
Auks 11.6.71 Auks (common guillemot and razorbill) are visual predators that commonly dive down to depths of around 60m (BWPi). They are wing- propelled divers which often dip their heads repeatedly into the water before diving and may be susceptible to substrate and prey movements caused by pile-driving activities. Both species also often feed swimming in lines, occasionally encircling and herding a shoal and catching fish at the periphery (BWPi). Their habitat use flexibility was assessed as medium (3
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out of 5) by Garthe and Hüppop (2004), although their sensitivity due to flexibility of habitat use was considered to be Low by Maclean et al. (2009). As a result, the GWF site-specific sensitivity to indirect disturbance is considered to be Medium for both common guillemot and razorbill.
11.6.72 As for the other species of principle concern, any temporary localised effects on foraging opportunities are likely to be no more than a Low magnitude impact. This would result in no more than a Minor adverse impact on the regional populations of either species.
11.6.73 A summary of predicted in-direct disturbance on species of principle concern are presented in Table 11.33.
Table 11.33 Predicted significance of in-direct disturbance of prey species on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible Migratory Negligible/ /SPA Not skua significant Common National Low Medium Low Regional Minor winter adverse guillemot
Common Regional Low Low Low Regional Negligible gull
Fulmar Regional Very Low Low Low Regional Negligible
Gannet Regional Very Low Low Low Regional Negligible
Great National Low Medium Low Regional Minor adverse black- backed gull
Great International Very Low Medium Negligible Migratory / Negligible / SPA Not skua significant Herring National Low Medium Low Regional and Minor / Not SPA significant gull
Kittiwake Regional Low Low Low Regional Negligible
Lesser International Very Low Medium High Regional and Minor / Not SPA significant black-
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude backed gull
Razorbill National Low Medium Low Regional Minor winter adverse Red- International High Very High Low Regional Minor / Not winter and significant throated SPA diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.7 Assessment of Impacts during the Operational Phase
11.7.1 This section provides an assessment of the potential impacts from the operational phase of the GWF project on offshore ornithology. Potential impacts from operational activities identified during the Scoping process and through consultation with the SNCAs and RSPB, Table 11.2, are associated with:
Direct disturbance of birds due to maintenance activities; Displacement of birds from an area around turbines effectively leading to habitat loss; Collision of birds with turbine rotors resulting in mortality; Attraction to lit structures; Barrier effects and fragmentation of habitats due to prevention of free movement; and Indirect effects on prey availability and distribution, and foraging/loafing habitat.
11.7.2 In general, operational effects are likely to last for the lifespan of the GWF (up to 25 years) and therefore will be long-term in nature. Effects may be permanent or reversible.
11.7.3 It is possible that some degree of habituation may result which would reduce impact levels over time, although in the case of collision mortality effects are unclear. For each species of principle concern, a consideration will be made as to whether the risk of collision mortality could increase, with birds active closer to the turbines, or, whether it may decrease if birds can deliberately avoid turbines. It should be noted that, for many species, there is a paucity of empirical evidence of these operational effects. Krijgsveld et al. (2010) found no evidence of habituation over the three years of ornithological monitoring at the OWEZ wind farm, the Netherlands, and so
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the potential for this effect is unclear. The spatial extent of disturbance- displacement may be less than the recommended entire buffer of out to 4km from GWF turbine areas for many species.
Direct Disturbance 11.7.4 Disturbance to birds due to operational offshore wind farms is considered to be of a lower intensity than during construction/decommissioning phases, and limited to maintenance activities as well as normal turbine activity, and also post-construction monitoring survey activity. The worst-case scenario for construction disturbance outlined in Table 11.29 applies equally here. Although the actual levels of maintenance required cannot be accurately predicted, they will be of a longer duration than construction, but likely more localised at any one time. Assuming that each turbine has to be checked at least once a year plus one or two extra visits per turbine to deal with technical problems, Exo et al. (2003) predicted that there may be more or less daily boating activities within the wind farm area, which will likely create more disturbance than the operating turbines themselves. It is expected that at GWF, four or five small operations vessels would be running each day during the operational period, which is likely to be much less intrusive to seabird species than construction activities.
Potential impacts on all seabird species of principle concern 11.7.5 Impacts are therefore likely to be of a lower significance to boat-based construction disturbance described above. It is therefore considered that although the period of maintenance will be longer-term than construction activity, it will be less intensive and extensive (e.g. no pile-driving), and so levels of significance will be no more than a Minor adverse impact for Very High sensitivity species (red-throated diver, lesser black-backed gull and great skua), and of Negligible impact for all other species.
11.7.6 A summary of predicted significance of effects is presented below in Table 11.34
Table 11.34 Predicted significance of direct disturbance on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible All levels Negligible skua
Common National Medium High Negligible All levels Negligible guillemot
Common Regional Low Low Negligible All levels Negligible
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude gull
Fulmar Regional Very Low Low Negligible All levels Negligible
Gannet Regional Low Low Negligible All levels Negligible
Great National Low Medium Negligible All levels Negligible black- backed gull
Great International Very Low Medium Negligible All levels Minor adverse skua
Herring National Low Medium Negligible All levels Negligible gull
Kittiwake Regional Low Low Negligible All levels Negligible
Lesser International Low High Negligible All levels Minor adverse black- backed gull
Razorbill National Medium High Negligible All levels Negligible
Red- International Very High Very High Negligible All levels Minor adverse throated diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Displacement 11.7.7 The displacement effects attributable to wind farms are variable and are species-, season- and site-specific. As displacement effectively leads to exclusion from areas of suitable habitat, it can be regarded as being similar to habitat loss in its effect on birds, although may be more spatially extensive. For breeding birds, the loss of foraging habitat may lead to a reduction in food supply, which in turn, can lead to reduced breeding success and individual survival or abandonment of the breeding territory. For overwintering birds the area may be a food source or used for moulting.
11.7.8 The biological consequences of such displacement and any resultant population-level effects will depend on the importance of the area from which birds are displaced and the capacity of alternative habitats to support
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these displaced birds. Migratory species are unlikely to find the area important unless it is recognised as an important staging area- there is no evidence of this in the GWF survey area.
11.7.9 For each of the species of principal concern, displacement effects associated with the presence of offshore infrastructure and maintenance traffic have been evaluated using the following information:
Evidence of the extent and duration of species’ sensitivity and avoidance of offshore turbines from the scientific literature (e.g. Petersen et al. 2006; Krijgsveld et al. 2010) and from vantage point survey carried out on behalf of GWFL at the operational GGOWF, Blyth Harbour and Haverigg Wind Farms in 2011; Evaluation of species’ sensitivity to habitat flexibility in Garthe and Hüppop (2004); Evaluation of species’ sensitivity to direct and indirect habitat loss, and flexibility of habitat usage in Maclean et al. (2009); Peak population estimates within the GWF study area and turbine areas alone; and The level of site usage in the GWF study area, for example feeding activity records and period of occurrence (e.g. annual, overwintering, migratory).
11.7.10 The likely worst-case scenario for displacement at GWF is outlined in Table 11.29. It presents the maximum number of turbines and ancillary infrastructure, with turbines spaced regularly, and up to the boundaries of Areas A, B and C, with no obvious corridors of access within. This provides for the maximum amount (spatial extent) of habitat loss due to displacement effects, without allowing access to some parts of the turbine areas for sensitive species.
11.7.11 Disturbance by operating wind turbines can exclude birds from suitable breeding, roosting, and feeding habitats around a larger area than otherwise would occur through direct habitat loss (Exo et al. 2003; Petersen et al. 2006; Maclean et al. 2009). Although some birds show no avoidance, others such as divers, auks and pelagic birds will not fly or forage within hundreds of meters of the turbines (Kerlinger and Curry, 2002). Comparatively, some gull species, cormorant and terns have not shown avoidance and were seen regularly foraging within OWEZ wind farm. Species such as gannet, scoter, guillemot and diver showed a stronger avoidance of the wind farm (Krijgsveld et al. 2010), Figure 104, Technical Appendix 11.A. A study at Tuno Knob, in Denmark, reported effects on nocturnal flights of eiders out to 1,500m from turbines (Tulp et al. 1999), Section 4.189, Technical Appendix 11.A.
11.7.12 Contrary to the findings above, other studies at operational wind farms have not observed significant effects on the abundance or distribution of local
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seabirds (Leopold et al. 2010; Barrow Offshore Ltd. 2009). With the exception of red-throated diver, monitoring at Kentish Flats Wind Farm also reported no avoidance behaviour (Percival 2009, 2010). It has been postulated that other natural environmental variables were the driver for any observed effects, as well as the influence of fishing vessels on some species (particularly gulls), Section 4.188-4.194, Technical Appendix 11.A.
11.7.13 Results from Vantage Point surveys carried out at the coastal wind farms of Blyth Harbour and Haverigg in July and August 2011 suggested that individual gulls regularly passed close to turbines, despite the relatively close spacing compared to GWF (see Annex 3 of Technical Appendix 11.A for full details). There is some evidence of habituation of local birds, particularly with regular diurnal flight corridors at Haverigg passing between turbine rows. No collisions were observed, and it follows that with larger spacing between turbines in the offshore environment, gulls will be able to use the space between turbines and outside risk areas, even in poor conditions. Vantage Point surveys within an operational area of GGOWF in June and July 2011 also demonstrated that gulls continue to use the wind farm despite the presence of turbines, as in only a small minority of cases were clear behavioural reactions of gulls recorded.
11.7.14 In general, migrants appear to be more obviously displaced than local residents, likely due to the lack of habituation of birds passing briefly through the area (Petersen et al. 2004; Petersen, 2005). Habituation is likely to occur for some species once turbines are operational and human activity is reduced. The study done at Blyth Harbour in the UK showed that eiders and other birds did habituate to the turbines so that impacts were not considered significant (Lowther 2000). Seaducks initially avoided the Horns Rev wind farm, but later assembled between turbines, possibly after successful recruitment of benthic prey (Petersen and Fox, 2007).
11.7.15 Foraging barnacle geese have been reported as being displaced from as far as 600m from wind turbines on farmland habitat in winter (Kowallik and Borbach-Jaene 2001) yet birds from the same population feed as close as 25m to turbines during spring staging on Gotland (Percival, 1998), where more nutritionally-valuable habitat was in close proximity to wind turbines. This shows that displacement from less preferred foraging areas may more readily occur than from more important ones. Also, as part of this assessment it is important to consider the ‘novelty’ of the GWF offshore infrastructure in the context of other sites across the region, Section 4.194, Technical Appendix 11.A.
Red-throated diver 11.7.16 Red-throated diver is rated as High sensitivity to flexibility of habitat use (i.e. it has specific habitat requirements) by Maclean et al. (2009) and Garthe and Hüppop (2004). As a species of International conservation value, the GWF site-specific sensitivity to displacement is considered to be Very High.
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11.7.17 Red-throated divers are likely to be sensitive to the presence of operational turbines. Comparison of pre- and post construction aerial surveys of waterbird abundance and distribution in and around the two Danish offshore wind farms demonstrated that diver at Horns Rev showed complete avoidance of the wind farm area during the three years’ post construction period, (Petersen et al. 2006), Section 4.195-Section 4.196, Technical Appendix 11.A.
11.7.18 At OWEZ, Krijgsveld et al. (2010) also observed that divers showed very strong avoidance, generally between 2 and 4km around the wind farm. Divers also showed strong avoidance of individual turbines. During post- construction monitoring surveys of local birds by Leopold et al. (2010), some divers were seen within the wind farm, but most were near the edges of the array. This shows that avoidance was less than 100%, and it was concluded that effects related to the presence of wind farms on the distribution pattern of local seabirds were mostly insignificant.
11.7.19 Surveys of the distribution and abundance of red-throated diver during the pre-construction, construction and post-construction phases of the Kentish Flats Wind Farm suggest that this species may be displaced from turbine areas and a buffer ranging between 500m and 2km, likely over the long term, with no obvious evidence of habituation, at least in the short term (Percival, 2010), Section 4.199-Section 4.200, Technical Appendix 11.A
11.7.20 The March 2009 peak of up to 112 birds in the GWF study area represents 1.4% of the regional wintering population and 1.7% of the Outer Thames SPA population, although is likely to consist of overwintering birds from outside of the region passing through on migration to breeding areas in northern Europe, Table 11.27. Further details of the assessment on habitat quality and possible displacement effects on red-throated diver can be found in Section 4.203- Section 2.221, Technical Appendix 11.A. Based on this information, it appears that in general, the GWF site can be classed as sub-optimal for the species, with abundant similar habitat to be found in the wider Thames Strategic Area, predominantly inshore. Although a relatively small area of substrate associated with the Outer Gabbard sand bank may be suitable for red-throated diver, this area is isolated from the majority of similar habitat in the region, and from previous surveys. The sightings distribution of red-throated diver within the GWF survey area strongly suggests that, compared to sighting densities further inshore, there is a weak association with this isolated pocket of offshore sandbank habitat.
11.7.21 Based on the evidence presented above, red-throated diver within the GWF are unlikely to be displaced between 2 and 4km, at least completely. This will likely reduce the impact on peak numbers affected to below <1% of their respective regional thresholds (Table 11.27).
11.7.22 Since it is evident that red-throated diver ranges widely across the southern North Sea (with 10,000-15,000 birds migrating through the Dover Strait, Stienen et al. 2007), it is unlikely that all birds displaced would be
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associated with the SPA (particularly as the peak population occurs in March during migration), thereby further reducing the likelihood of significant effects on its population.
11.7.23 Although red-throated diver may regularly redistribute across the Thames Strategic Area in response to food sources, the waters within and adjacent to the GWF consistently show the lowest wintering diver densities (DTI, 2006). With the exception of the spring migration in 2005/06 were numbers relatively high. It is likely that any displacement of low numbers of red- throated diver could be absorbed by a number of adjacent inshore areas, and also around The Wash, which would dilute any displacement effects on regional and Outer Thames SPA populations to insignificant levels, resulting in a negligible impact magnitude at any level..
11.7.24 It is, therefore, concluded that displacement will create at worst a long-term Minor adverse impact on the regional population, and a Non- significant adverse impact on the Outer Thames SPA population, see Section 11.3.60 and the HRA Report.
Lesser black-backed gull 11.7.25 Lesser black-backed gull are more flexible to changes in habitat (Table 11.6). However, as their conservation status is Very High, the GWF site- specific sensitivity is rated as High.
11.7.26 Monitoring surveys at GGOWF have shown that lesser black-backed gull show no obvious displacement effects during construction, often perching on turbine bases and other ancillary structures (GGOWL, 2010). Evidence of this apparent non-avoidance of certain gull species to operational wind farms is provided by studies at Petersen et al. (2006); Leopold et al. (2010); Krijgsveld et al. (2010); Everaert (2006, 2008, 2011); Everaert and Kuijken (2007); Lawrence et al. (2007) and Krigjsveld et al. (2009). Details of all these studies can be found in Annex 3 of Technical Appendix 11.A.
11.7.27 This empirical evidence suggests it is unlikely that displacement will take place out to the recommended worst-case 4km buffer (Maclean et al. 2004) and would realistically be confined, at worst, to the GWF turbine areas alone. In actuality, evidence of displacement is only likely to be recorded immediately adjacent to individual turbines, with negligible impact the survival of lesser black-backed gull at any level.
11.7.28 The peak population estimate for the GWF site was 2,047 birds in early January 2009, which represents four times the national wintering population threshold and an average of 759 (516-1,001) birds in June which represents 0.3% of the national summer population estimate. These figures also represent around 7% of the regional winter population, 10% of the regional breeding population and 63% of the current Alde-Ore Estuary SPA population.
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11.7.29 Lesser black-backed gull forage widely across the Greater Thames and southern North Sea, although the GWF site appears to be important for the species within a regional context, evidence from various operational wind farms suggests that gulls will be unaffected by the presence of the turbines. Through analysis of boat-based surveys, Schwemmer and Garthe (2005) and Camphuysen et al. (2008) found a significant association between the offshore distribution of certain gull species and commercial fisheries. This association pattern was regularly observed during the GWF boat-based surveys. It follows that, in the future, these gulls are likely to follow fishing vessels into the wider area after fishing activities reduce within the operational wind farm. Such evidence may have been already observed from vantage point surveys at GGOWF in 2011 (Annex 4 of Technical Appendix 11.A), where flight activity levels, and in particular flock sizes, were much lower than recorded during GWF baseline surveys during similar months. With no fishing vessels present during vantage point surveys (potentially due to the 500m construction exclusion zone, even though no construction took place within the vicinity), birds did not generally forage in flocks within the site, and utilisation was mainly confined to transit flights.
11.7.30 It is, therefore, considered that displacement will create, at worst, a long- term Minor adverse impact on the regional population.
11.7.31 Due to the fluctuation in breeding pairs within the Alde-Ore Estuary SPA, Section 11.4, the confidence in estimating the level of significance on the SPA population is low. Data collected by Schwemmer and Garthe (2005) for Dutch colonies indicated a slightly more contracted foraging range during May-June in comparison to July-August, possibly as the end of breeding activity allows foraging at longer distances from the shore, in areas of higher food availability provided by fishing vessels. This means that it is likely that a large proportion of birds found in the GWF site are from the SPA, and therefore if unmitigated, a significant effect on the SPA population is a possibility. However, with the species’ likely tolerance of both the wind farm as a whole, and of individual turbine structures, it is considered likely that there will be a Non-significant impact on the SPA population in the long-term, see Section 11.3.60 and the HRA Report.
Other gulls 11.7.32 A number of other gull species (herring gull, common gull, great black- backed gull and kittiwake) forage within the GWF site. Similar to lesser black-backed gull, these species are considered to have a low sensitivity to habitat change and therefore displacement (Table 11.6). They are all wide- ranging across the outer Thames Estuary and are unlikely to be displaced to any great extent by the presence of GWF turbine array.
11.7.33 Birds regularly fly between closely-spaced turbines at the Blyth Harbour and Haverigg coastal wind farm sites, and there is evidence, particularly at Haverigg, that habituation has occurred, with regular flight corridors
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between turbines (see Annex 3 of Technical Appendix 11.A for further details).
11.7.34 Considering the GWF study area in isolation, estimated numbers of herring gull and common gull did not reach regional significance and so displacement will result in Negligible adverse impacts on regional populations, since a large proportion of the herring gull observed at the GWF are unlikely to be from the small regional population. The Alde-Ore Estuary SPA herring gull population has an unfavourable conservation status, the peak count during summer months was 25 individuals (May 2010), which suggests that the site is relatively unimportant for the species, and beyond regular foraging range. Therefore, No significant adverse impacts are predicted on the Alde Ore SPA herring gull population.
11.7.35 Kittiwake was found within the GWF site in regionally-important numbers (172 birds in April 2010) which would result in a High magnitude adverse effect. Combined with the low GWF site-specific sensitivity for these species, this would result in Minor adverse impacts on the regional population.
11.7.36 Great black-backed gull was found in numbers that exceeded the 1% national threshold in early January 2009, although estimated numbers did not approach this level in any other survey month. The loss of the GWF site population (436 individuals) would present a Low magnitude impact on the regional winter population. As a result of the GWF site-specific sensitivity (Medium) a Minor adverse impact is predicted on the national and regional populations at worst. Although a peak of 12 birds in summer months is theoretically significant to the small regional breeding population, it is unlikely that breeding pairs would use the site as it is outside of the core foraging range of up to 40km (Ratcliffe et al. 2000).
Fulmar and gannet 11.7.37 Northern fulmar were found within the GWF site in regionally-important numbers in early January 2009, which would result in Medium magnitude adverse effect, although the regional winter population was considered in the Species Accounts section to be a large underestimate. Combined with the low GWF site-specific sensitivity for this species, this would result in a Minor adverse impact on the regional population.
11.7.38 Although gannet show Very Low sensitivity to habitat change (Table 11.6), the species has generally been observed to show strong avoidance of wind farms (Krijgsveld et al. 2010;Vanermen and Stienen. 2009), Section 4.233, Technical Appendix 11.A and Annex 3 of Technical Appendix 11.A. Gannet was found within the GWF site in regionally-important numbers in early November 2008 and April 2010, which would result in Low magnitude adverse effects on the winter and summer populations, assuming complete avoidance. As a result of the GWF site-specific sensitivity (Low), a worst- case Minor adverse impact is predicted on the regional population.
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Skuas 11.7.39 Arctic skua and great skua are both assessed as having Very Low general sensitivity to habitat impacts (Garthe and Hüppop (2004) and Maclean et al. (2009), Table 11.6, which is a reflection of their flexible foraging strategies and wide foraging range. Observations by Krijgsveld et al. (2010) at the OWEZ wind farm suggest that skua are unlikely to be displaced beyond the GWF site as a whole, Section 4.238-4.240 of Technical Appendix 11.A.
11.7.40 In the case of GWF, both species are present only within brief periods during autumn migration, and so the site is unlikely to be important for the species. Despite the possibility that the peak passage volumes may have been missed, numbers of Arctic skua that are potentially affected do not reach importance at any level (Negligible magnitude). It is acknowledged that the confidence in this prediction is low due to the possibility of peak passage numbers going unrecorded, and therefore displacement effects may have a Minor adverse impact on the migratory population and a non-significant impact on any SPA population. Refer to Appendix D of the HRA Report.
11.7.41 A peak average of 31 (5-56) great skua in the GWF site in September 2008 is considered to be around 0.1% of the migratory North Sea population, and therefore a displacement impact may be of Negligible magnitude on this Medium GWF site-specific sensitivity species. However, as the confidence in this is low, a Minor adverse impact is predicted on the migratory population, and a non-significant impact on any SPA population. Refer to Appendix D of the HRA Report.
Auks 11.7.42 Common guillemot and razorbill populations are of National conservation value although the species are rated as being of Low sensitivity to habitat flexibility by Maclean et al. (2009), Table 11.6, as both species are wide- ranging, particularly during winter months. However, both species are considered to have a Medium general sensitivity to disturbance, resulting in a GWF site-specific sensitivity of High.
11.7.43 Vanermen and Stienen (2009) and Petersen et al. (2004 and 2005) reported that auks may have shown evidence of displacement up to 4km from operational turbines. However the authors noted that uncertainty surrounding the effects of the wind farm and changes in other environmental covariates, Section 4.242, Technical Appendix 11.A.
11.7.44 Within the GWF study area (the wind farm footprint and out to 4km buffer), 3,219 (879-5,559) common guillemot (5.8% of the regional population) and 342 razorbill (5.6% of the regional population) were recorded during the boat surveys in February 2009. Based on Table 11.8, the highly precautionary assumption that all birds would be displaced from the entire GWF study area would represent a Medium impact magnitude on the regional population. However, as reported in Section 11.4, auks range
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widely in the offshore areas of the Greater Thames during winter months, particularly from November to February (Stone et al. 1995). There is no consistent evidence that GWF site, in isolation, represents an important area for auks and it follows that alternative habitat would be available in the Greater Thames beyond the limits of the temporary displacement.
11.7.45 Based on the evidence of the displacement of auks from other operational wind farms, it is considered unlikely that all razorbill and common guillemot would be displaced out to 4km and may be closer to th 1-2km buffer. The magnitude of any losses is, therefore, more likely to be Low for both species, which would result in a Moderate adverse impact of a long-term duration on the regional winter population of common guillemot and razorbill, which is considered tolerable based on both species’ relatively favourable long-term population status and also the wide-ranging foraging behaviour of birds during the winter period in response to prey movements.
11.7.46 A summary of the predicted impacts due to operational displacement on species of principal concern is presented in Table 11.35
Table 11.35 Predicted significance of operational displacement on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible Migratory Minor skua
Common National Medium High Moderate Regional Minor winter guillemot
Common Regional Low Low Negligible Regional Negligible gull
Fulmar Regional Very Low Low Medium Regional Minor Winter Gannet Regional Very Low Low Low Regional Minor
Great National Low Medium Low National and Minor regional black- backed gull
Great International Very Low Medium Negligible Migratory Minor skua
Herring National Low Medium Negligible / Regional / Negligible / Low SPA Not
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude gull significant
Kittiwake Regional Low Low High Regional Minor
Lesser International Low High Medium/ Regional / Minor / Not High SPA significant black- backed gull
Razorbill National Medium High Moderate Regional Minor winter Red- International High Very High Medium Regional Minor winter and throated SPA diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Collision with wind farm infrastructure 11.7.47 Seabirds may collide with wind turbines and associated structures, the result of which would almost certainly be lethal to that individual. Ornithological monitoring at a number of operational wind farms have reported low levels of avian mortality, it is thought that many seabirds are able to take avoiding action (Drewitt and Langston 2006). The actual risk of collision depends on a number of factors including the location of the wind farm, the bird species using the area, weather conditions and the size and design of the wind farm (including the number, size of turbines and use of lighting).
11.7.48 Further details on the types of bird movements which may influence collision risk, as reviewed by Kerlinger and Curry (2002), can be found in Section 4.282 of Technical Appendix 11.A.
11.7.49 The effect of an individual loss on a population is influenced by several characteristics of the affected population: notably its size, density, recruitment rate (additions to the population through reproduction and immigration) and mortality rate (the natural rate of losses due to death and emigration). In general, the effect of an individual lost from the population will be greater for species that occur at low density, are relatively long-lived and reproduce at a low rate. Most seabird species fall into this category. Conversely, the effect will often be insignificant for shorter-lived species with higher reproductive rates found at high densities, which includes some of the smaller gulls. Species that habitually fly at night or during low light conditions at dawn and dusk may also be at increased risk from collisions,
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although both eiders and scoters have been shown to detect and avoid offshore turbines at night (Winkelman 1995 and Tulp et al. 1999).
11.7.50 It should be noted that operational disturbance/displacement and collision risk effects can be mutually exclusive in a spatial sense i.e. a bird that avoids the wind farm area cannot be at risk of collision with the turbine rotors at the same time. However, they are not mutually exclusive in a temporal sense; a bird may initially avoid the wind farm, but habituate to it, and would then be at risk of collision. In addition, birds may generally avoid wind farms, but during periods of poor visibility may fly closer to turbines before taking avoiding action.
11.7.51 In general, effects of increased mortality on populations due to collisions with turbines are considered to be long-term (i.e. throughout the operational wind farm’s lifespan) and it is assumed that in the model, collision rate does not decrease in response to losses in the population, Section 4.285, Technical Appendix 11.A. In reality, effects may change over time, as birds, particularly residents near the site, may become habituated to the presence of turbines, or external factors, such as changes in fishing activities, may alter the attractiveness of the wind farm area to birds, thereby changing activity levels within. Due to a variety of external factors such as climate change, predation levels and changes in prey distribution that are unrelated to the wind farm, it is difficult to predict with any confidence the long-term effects of collisions on a population, and the permanency of such effects.
Methodological approach to Collision Risk Modelling
11.7.52 The defined worst-case scenario, Table 11.29, is considered for 140 wind turbines with a rotor diameter of 120m and a minimum lower rotor tip clearance of 22m above MHWS. This comprises the option with the most structures in the wind farm footprint, combined with the rotor diameter that results in the greatest rotor swept area to wind farm area ratio. The Siemens 3.6MW 120m turbines provide the lowest rotor tip height of 22m above MHWS- hence the inclusion of flights within a 20-30m height band, which are numerous compared to those at higher altitudes. It is assumed that turbines are distributed evenly between Areas A, and B and C.
11.7.53 For the purposes of assessing collision mortality, MacLean et al. (2009) have outlined a recommended process for offshore wind farms, based on the developed methods for onshore wind farms recommended by SNH (Band et al. 2007). This method uses the mean number of birds in flight at any time during a particular month, taken from snapshot counts within each turbine array during boat-based surveys. For a detailed account of the methods and input parameters for the GWF Collision Risk Modelling (CRM), refer to Section 4.295-Section 4.306, Technical Appendix 11.A.
11.7.54 Not all species’ populations are likely to be affected to any significant extent by any predicted increases in additional mortality from collisions, either due
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to low numbers of flights recorded within GWF turbine areas, or behaviour that indicates that the species is not susceptible to collisions. Therefore, available baseline data and information on species’ ecology were used to screen which species will be included in CRM. For a detailed account of the species selection process for CRM, refer to Section 4.288-Section 4.294, Technical Appendix 11.A.
11.7.55 During consultation with the JNCC and Natural England, GWFL were advised to explore the approach to migratory species in more detail, Table 11.2. Although the total number of migratory species recorded in snapshot appeared very low for Arctic skua and great skua, the majority of these flights are from the same survey month; therefore, additional mortality rates may be significant during this brief period (autumn migration). Passage species, therefore, require a different treatment to more regularly-occurring species such as local breeders. One of the key considerations is to account for the passage rate of the migrant birds through the wind farm site which may not be captured by the ‘snapshot’ boat-based or aerial surveys.
11.7.56 It was suggested by the JNCC and Natural England (Table 11.2) that the numbers seen on surveys could be scaled up to estimate the peak volumes of migrants passing through the site and compare this with known populations (e.g. within SPAs) and their migratory flyway routes to produce a measure of the importance of the GWF population. However, GWFL does not consider that it would be possible to accurately predict peak passage rates for any migratory species, using the data that are available and, therefore, any increases in numbers would not be founded on any scientific evidence. Section 4.292 of Technical Appendix 11.A describes how, in the CRM for both skua species, the highest monthly density estimate for either of the GWF study area was used for each month of the autumn migration period (July to September). This approach is considered to be very precautionary, based on the assumptions already incorporated into the CRM, whereupon densities are maintained throughout the period of interest. Therefore, if the peak snapshot count is used for the entire migratory period, this will likely produce considerably higher numbers of flights through the wind farm during the period than would likely occur.
11.7.57 As an example, the CRM for great skua estimated that the monthly number of great skua flights within the turbine areas (at all heights) were between 123,000 to 162,000, depending on the amount of hours potentially active each month. When considering the total flyway population of 27,200 individuals, this would mean that each bird would have up to six flights within the turbine areas, which is considered very unlikely. This situation is considered for migratory species in the impact assessment.
Avoidance rates
11.7.58 As described in Section 4.307 of Technical Appendix 11.A, avoidance rate is the most sensitive parameter for calculating predicted mortality rates (Chamberlain et al. 2006).
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11.7.59 The current advice from the JNCC and Natural England is based on guidance by SNH (2010), which suggests that an avoidance rate of 98% should be used as the default for most species (including gulls, terns and divers) until sufficient evidence is available to show otherwise, Table 11.2.. It should be noted that the ‘lower’ 98% avoidance rates presented in SNH (2010) are not based on specific empirical evidence and are generally seen to be over-precautionary in the context of MacLean et al (2009), Section 4.308 of Technical Appendix 11.A.
11.7.60 It is recognised that there remains a significant knowledge gap regarding the general flight behaviour of seabirds around operational offshore wind farms, and specifically their avoidance rates of both wind farms as a whole, and individual turbines (for example, Chamberlain et al. 2006; Maclean et al. 2009; Cook et al. In Prep).
11.7.61 For the purposes of this assessment, GWFL has undertaken a detailed literature review of collision risks of seabirds at various operational wind farms in an attempt to quantify associated avoidance behaviour for key species of principle concern, Annex 3 of Technical Appendix 11.A.
11.7.62 Generally, studies have estimated either micro avoidance of macro avoidance rates, and so a combination of both is required in order to be able to estimate ‘true’ avoidance rates for use in the Band CRM and impact assessment for GWF. For a summary of the results from this literature review, refer to Section 4.311-Section 4.323 of Technical Appendix 11.A.
11.7.63 Evidence from the vantage point surveys and literature suggests that a 99% avoidance rate is the most realistic level for gull species in the offshore environment. This supports the approach for considering a mortality rates based on range of avoidance rates.
Results of the GWF Collision Risk Model
11.7.64 Mortality rates, based on avoidance rates from 98.0% to 99.5%, are presented for each species. From the resultant monthly and annual mortality rates predicted, the magnitudes (and subsequently the significance) of the effects of collisions for each species are assessed by determining the increase in additional mortality over the baseline rate of a population, taken from the inverse of the annual survival rates presented in Table 58 of Technical Appendix 11.A. These mortality rates are compared against (if available or applicable) the regional breeding and wintering populations; national breeding and wintering populations; and international/biogeographic breeding and wintering populations. As seabirds are relatively long-lived with low reproduction rates, small increases above the natural rate of mortality may result in significant population changes.
11.7.65 Results of the CRM for June 2008 to May 2009 (year 1) and June 2009 to May 2010 (year 2) surveys are shown below for each species of principle
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concern, Table 11.36 and Table 11.37. Full details of the monthly collision risk rates are presented in Tables A.7 to A.24 in Annex 1 of Technical Appendix 11.A.
Table 11.36 Annual collision rate predictions, 2008/09
2008/09 Red-throated diver diver Red-throated Gannet Arctic skua Great skua Common gull gull Lesser black-backed Herring gull gull Great black-backed Kittiwake Area A
98% avoidance 1.0 73.4 3.6 24.4 2.4 328.5 29.9 59.2 74.7
99.0% avoidance 0.5 36.7 1.8 12.2 1.2 164.2 15.0 29.6 37.4
99.5% avoidance 0.3 18.3 0.9 6.1 0.6 82.1 7.5 14.8 18.7
Areas B and C
98% avoidance 0.1 38.4 0.0 2.6 1.5 332.3 18.7 44.7 17.1
99.0% avoidance 0.1 19.2 0.0 1.3 0.7 166.2 9.4 22.3 8.6
99.5% avoidance 0.03 9.6 0.0 0.6 0.4 83.1 4.7 11.2 4.3
Total annual 111. 103. mortality 1.1 3.6 27.0 3.9 660.8 48.6 91.8 8 9 (98% avoidance)
Total annual
mortality 0.6 55.9 1.8 13.5 1.9 330.4 24.4 51.9 46.0
(99% avoidance)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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Table 11.37 Annual collision rate predictions, 2009/10
2009/10 Red-throated diver diver Red-throated Gannet Arctic skua Great skua Common gull gull Lesser black-backed Herring gull gull Great black-backed Kittiwake Area A
98% avoidance 0.6 31.2 0.0 0.0 14.9 276.1 85.8 29.5 104.2
99.0% avoidance 0.3 15.6 0.0 0.0 7.5 138.1 42.9 14.7 52.1
99.5% avoidance 0.1 7.8 0.0 0.0 3.7 69.0 21.4 7.4 26.1
Areas B and C
98% avoidance 0.0 60.0 0.0 0.0 3.0 174.0 23.1 46.2 43.9
99.0% avoidance 0.0 30.0 0.0 0.0 1.5 87.0 11.5 23.1 22.0
99.5% avoidance 0.0 15.0 0.0 0.0 0.7 43.5 5.8 11.5 11.0
Total annual mortality 0.6 91.2 0.0 0.0 17.9 450.1 108.9 75.7 148.1 (98% avoidance)
Total annual mortality 0.3 45.6 0.0 0.0 9.0 225.1 54.4 37.8 74.1 (99% avoidance)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.7.66 Using the annual mortality figures obtained from summing the monthly estimates in Tables A.7 to A.24 in Annex 1 of Technical Appendix 11.A, an estimate can be made on the increase to baseline mortality rates on the respective biogeographic populations during breeding and/or winter periods. The annual mortality rates from 2008/09 and 2009/10 have been used to estimate increases on baseline mortality rates for the international (Table 11.38), national (Table 11.39) and regional breeding and/or wintering populations (Tables 11.40).
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Table 11.38 Comparison of peak annual mortality rate with increases to baseline international mortality rates
Species Baseline mortality rate Baseline mortality rate mortality Annual breeding pop. International (pairs) mortality Additional wintering International pop. (individuals) mortality Additional Red- 0.17 0.6-1.1 32-92,000 <0.01% 300,000 <0.01% throated diver
Gannet 0.10 91.2-111.8 300,000 0.1-0.2% 300,000 0.3-0.4%
Arctic skua 0.17 0.0-3.6 40- <0.01% ? ? 140,000
Great skua 0.12 0.0-27.0 16,000 <0.7% ? ?
Common 0.22 1.9-9.0 590,000- <0.01% 2.0m <0.01% gull 1.9m
Lesser 0.10 225.1- 300- 0.4-0.5% 550,000 0.4-0.6% black- 330.4 350,000 backed gull
Herring gull 0.10 24.4-54.4 760,000- <0.02% 590,000 <0.1% 1.4m
Great 0.10 37.8-51.9 110- 0.1-0.2% 440,000 <0.1% black- 180,000 backed gull
Kittiwake 0.17 46.0-74.1 2.1-3.0m <0.01% 2.0m <0.01%
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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Table 11.39 Comparison of peak annual mortality rate with increases to baseline national mortality rates
Species Baseline mortality rate Baseline mortality rate mortality Annual pop. breeding National (pairs) mortality Additional pop. wintering National (individuals) mortality Additional Red-throated 0.17 0.6-1.1 1,255 0.1-0.2% 17,000 <0.1% diver
Gannet 0.10 91.2-111.8 218,546 0.2% 430,710 0.2%
Arctic skua 0.17 0.0-3.6 2,136 <0.5% ? ?
Great skua 0.12 0.0-27.0 9,364 <1.2% 19,300 <1.2%
Common gull 0.22 1.9-9.0 48,163 <0.01% 429,331 <0.01%
Lesser black- 0.10 225.1- 110,101 1.0-1.5% 60,830 3.7-5.4% backed gull 330.4
Herring gull 0.10 24.4-54.4 131,469 <0.2% 376,775 <0.1%
Great black- 0.10 37.8-51.9 17,084 1.1-1.5% 43,108 0.8-1.2% backed gull
Kittiwake 0.17 46.0-74.1 366,832 <0.1% 733,700 <0.1%
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Table 11.40 Comparison of peak annual mortality rate with increases to baseline regional or migratory mortality rates Species Baseline mortality rate Baseline mortality rate mortality Annual pop. breeding Regional (pairs) mortality Additional or migratory Regional (individuals) wintering pop. mortality Additional Red-throated 0.17 0.6-1.1 0 n/a 7,998* <0.1% diver
Gannet 0.10 91.2-111.8 0 n/a 40-60,000** 1.8-2.2%
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Species Baseline mortality rate Baseline mortality rate mortality Annual pop. breeding Regional (pairs) mortality Additional or migratory Regional (individuals) wintering pop. mortality Additional Arctic skua 0.17 0.0-3.6 0 n/a ? ?
Great skua 0.12 0.0-27.0 0 n/a 27,200** <0.8%
Common gull 0.22 1.9-9.0 0 n/a 20,527* <0.1%
Lesser black- 0.10 225.1- 3,520 32-47% 125,000** 1.8-2.6% backed gull 330.4
Herring gull 0.10 24.4-54.4 2,261 10-23% 64,172* 0.4-0.8%
Great black- 0.10 37.8-51.9 8 4,725- 25,117* 1.5-2.0% backed gull 6,487%
Kittiwake 0.17 46.0-74.1 1,598 37-59% 30,467* 0.9-1.4%
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A. * = resident population; ** migratory population in southernmost North Sea. Usage of reference population depends on seasonal distribution of species within the GWF study area.
11.7.67 An assessment of collision mortality has been made based on annual mortality, using avoidance rates informed by the best available evidence. Resultant collision rates may be considered as being at best precautionary and, perhaps in some cases, may be a significant overestimate of actual mortality, refer to Section 4.331 of Technical Appendix 11.A for a discussion of the limitations and assumptions which underpin the CRM outputs:
Red-throated diver 11.7.68 Compared with other seabird species, red-throated divers have previously been considered to be relatively vulnerable to collision risk at wind farms due their biology and behaviour (Garthe and Huppop, 2004). Contrary to these concerns however, predominantly fly below rotor height (for example, Cook at al In Prep), and can use much of the airspace up to at least 1,000m on migration (BWPi), and there has been only one incidence of a red- throated diver collision in Europe (Hötker et al. 2006).
11.7.69 Although their biology suggests that birds may be prone to collision, evidence from operational wind farms shows that the species has strong macro avoidance of wind farms. In addition, very few flights are at potential
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rotor height (Cook et al. In prep). The species is thus considered of Medium general sensitivity to collision risk. As a species of International conservation value, the resultant GWF site-specific sensitivity to collision risk is rated as being Very High.
11.7.70 Records of birds in flight during GWF boat-based surveys indicate that flight heights were predominantly below potential collision risk height, PCH, (98%) and, therefore, a low collision risk is likely. This corresponds from findings at other wind farm sites in Cook et al. (In Prep.). A peak collision rate of 0.6 birds per year was predicted for the GWF site (Area A and Areas B and C) in 2008-09.
11.7.71 In the context of the baseline annual mortality for red-throated diver (15- 20% predicted by Maclean et al. (2009), applied to Outer Thames SPA this would equate to 970-1329 deaths per annum; and for the regional population would be 1,200-1,600 deaths per annum), an additional 1.1 deaths per year as a result of interactions with GWF would constitute an impact of Negligible magnitude at all scales. Resulting in a Minor Adverse Impact on the regional red-throated diver population and a non- significant impact on the SPA population. Refer to the HRA Report for more detail.
Gannet 11.7.72 Garthe and Hüppop (2004) suggest that gannet predominantly fly between 10 and 20m and generally would therefore not likely be at risk from collisions with turbines, even if they do not show any avoidance behaviour near a wind farm. A mean flight height of 10m ABSL was determined by Cook et al. (In Prep.) from 24 studies at 22 sites. Only 8% of flights recorded during GWF surveys were at risk height. Evidence of gannet behaviour at operational wind farms (e.g. Petersen et al. 2006; Krijgsveld et al. 2010, who showed at least a 90% reduction in numbers) suggest that birds do strongly avoid wind farms as a whole. The GWF site-specific sensitivity was rated as Low for this Regional conservation value species.
11.7.73 Table 11.38 and Table 11.39 suggest that a peak annual gannet mortality of 112 birds is of Negligible magnitude at the international and national levels. This would be considered a Low impact magnitude (1.8-2.2%) if it is assumed that all birds lost derive from the southernmost North Sea migratory population, which is considered to be the most accurate estimate of the winter gannet population, with the majority of birds recorded within the GWF during passage periods.
11.7.74 When considering the gannet breeding colonies that likely contribute to migratory passage, Table 11.41, it is assumed that each colony are equally likely to pass through the GWF site.
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Table 11.41 Gannet breeding colonies in the East and Southern North Sea.
Site Survey Colony count Distance from Date (occupied nests) GWF
Bempton Cliffs 2009 7,859 c.275km
Troup, Pennan and Lion's 2010 2,787 c.700km Heads
Bass Rock 2004 48,065 c.530km
Total 58,711
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11. Data from the JNCC’s Seabird Monitoring Programme database.
11.7.75 A significant level of impact on Flamborough Head and Bempton Cliffs SPA is considered unlikely, as the SPA population forms only 3.6% of the British breeding population, and 11.9% of the east and south North Sea population. A colony count at Flamborough Head and Bempton Cliffs SPA in 2008 also estimated that there would be at least 2,500 non-breeding individuals present, which are likely to contribute at least equally to mortality rates. As most British birds are likely to move to southern Europe outside of the breeding season (at least October to January), the period of time each year where SPA birds are at risk is likely smaller, thereby reducing mortality rates.
11.7.76 It is, therefore, unrealistic to assume all birds passing through offshore wind farm sites along the east coast will be from this SPA. The GWF site is 275km from the SPA and barely within the species’ mean maximum foraging range, 300km, (Langston, 2010). Evidence from satellite-tagged birds at Bempton Cliffs suggest that the mean and maximum foraging ranges of breeding birds were much smaller than the distance to the GWF site, and there was no evidence that any birds reached as far south, at least during the extended breeding season to October (Langston, 2011). Birds found within the GWF site during the breeding season are, therefore, more likely to be mainly wandering non-breeders and sub-adults un-attached to this Bempton Cliffs SPA. Breeding birds found in the GWF that originate from the SPA are likely to pass through once or twice per season on migration, particularly during autumn and, therefore, are at negligible risk from collision. Table 11.39 suggests that collisions with GWF will result in a peak annual mortality rate of 91.2-111.8 gannet, which equates to a negligible magnitude increase in additional mortality for the national population (0.2%) and low magnitude increase for the regional or migratory population (1.8%-2.2%).
11.7.77 There is predicted to be a Minor adverse impact on the regional winter population. No SPA populations are likely to have significant impacts, refer to the HRA Report.
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Skuas 11.7.78 The GWF site-specific sensitivity for Arctic skua is considered to be Medium, based on its International conservation value and the results of Cook et al. (in prep) that suggest around 10% of flights are likely to be at rotor height. Using peak snapshot counts for the entire autumn migration period, the estimated peak annual collision risk was 3.6 birds, which was considered to increase the baseline mortality of the national breeding population by <0.5% (Table 11.39). This would be considered an effect of Negligible magnitude which results in a Negligible adverse impact on the national population.
11.7.79 When considering the UK SPA population of 780 pairs, there would be an increase in baseline mortality of 2.3%, if it is assumed that all deaths result from SPA breeding bird collisions. This magnitude of impact is considered highly unlikely with the age of first breeding occurring at 4-5 years (BWPi) a large proportion of birds recorded will be immatures that do not form part of the breeding population. Monitoring of the Shetland breeding colonies suggests that between 12% and 50% of adults did not breed in any year (Klomp and Furness, 1992). Combined with the possibility that birds may migrate from other northern European colonies, the impacts of collision mortality on UK SPAs are considered to be Not Significant, see Section 11.3.60 and Appendix D of the HRA Report.
11.7.80 The site-specific sensitivity of great skua was considered to be Medium (Table 11.6), largely based on the potential connectivity of migratory birds with UK SPAs (International conservation value). Table 11.39 suggests that a peak estimate of 27 birds would be killed in one year. The predicted increase in mortality rate on the national population (9,364 pairs) was calculated as reaching up to 1.2%. This is considered unlikely as it is doubtful that all mortality (0-27 great skua per annum) is from the national population. Up to 100% of the flyway population (27,200 birds) passes through the Dover strait each year on migration (Stienen et al. 2007), and with snapshot counts being confined to the autumn passage period, it is likely that any collisions would be limited to these discrete migratory periods, which is predicted to be insignificant at this level (0.8%). Therefore, the impact of collisions on the great skua migratory and national populations is considered Negligible.
11.7.81 When considering the UK SPA population of 6,262 pairs, a total of 27 deaths would increase the baseline mortality by 1.8%, which would be potentially significant, particularly when it is evident that west coast Scottish birds (from two colonies) tend to migrate southward down the Atlantic coast rather than the North Sea. However, based on a combination of the presence of non-breeders and immatures, as well as birds from non-SPA colonies (approximately one third of the UK breeding population), it is likely that the significance of additional mortality will drop below 1%. As such No significant impacts are predicted for any SPAs, see Section 11.6.30.
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Lesser black-backed gull 11.7.82 Predicted lesser black-backed gull annual mortality was relatively high, with a range of 225-330 individuals at a 99% avoidance rate. The species regularly occurred in snapshot throughout the year, although the highest numbers were recorded in the late breeding and post-breeding period, Tables A.17 and A.18, Annex 1 of Technical Appendix 11.A.
11.7.83 When interpreting the effects of annual mortality, it is important to consider the temporal-spatial distribution of lesser black-backed gull within the GWF study area across the year. For example, such mortality rates would result in a Negligible magnitude effect on the international breeding and winter populations (0.4-0.6% additional mortality), and a Negligible impact on the international population when considering a High site-specific sensitivity for the species. This figure assumes that birds from the breeding population and winter population would be present on site all year round. This is considered unlikely, and evidence for this is presented in full in the Information to Inform an Appropriate Assessment in the HRA Report.
11.7.84 Due to the migratory nature of the UK and European populations, it is unlikely that birds from the SPA breeding population and winter population would be present in the GWF study area all year round. It is likely that the majority of coastal breeders within the region migrate southwards after breeding, and are present on site between March and August only (Thaxter et al., 2011).
11.7.85 The highest collision mortality at GWF was predicted to occur in the late breeding season and subsequent migration period. Recent tagging studies at the Texel breeding colony suggests that a proportion of adults from major colonies in the Netherlands and Belgium are present at the site throughout the summer. In contrast, winter activity is relatively low, suggesting that the majority of lesser black-backed gull will have left the area.
11.7.86 Monthly collision rates presented in Tables A.17 and A.18, Annex 1 of Technical Appendix 11.A show that between 50% and 73% of annual mortality occurs during the breeding season (when considering the 2009 March-August data as a full breeding season) and, as most of the national breeding population will migrate further south or be found inland over winter, it is therefore considered realistic to predict that there will be a Minor adverse impact on the national breeding population, with most UK birds only likely to be using the site during the breeding season.
11.7.87 The magnitude of additional mortality on the British winter population is also considered to be Low (4-5% increase), although it follows from the previous paragraphs that mortality during the winter period will only account for a minority of the annual total, and so the actual magnitude of impact will be lower. Evidence provided in Section 4.358 of Technical Appendix 11.A, suggests that the British lesser black-backed gull population is substantially enhanced by influxes of Icelandic, Faroese and other continental birds, the latter involving graellsii, intermedius and fuscus subspecies (e.g. Rock,
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2002; Helberg et al. 2009). This would again dilute the effects of any collision mortality, resulting in a Minor adverse impact on the national wintering population.
11.7.88 Although the residential regional population along the Suffolk coast in winter evidently declines greatly (BTO WeBS data and Landguard Bird Observatory ringing data, 2011), the species migrates in very large numbers through the North Sea in winter months, to areas much further south (an estimated 125,000 individuals passing through the Dover strait each year – Stienen et al. 2007). This figure is considered to be the most realistic reference population to use for regional winter impacts, rather than the maximum resident population. Collision mortality results in an additional 2-3% on baseline mortality, which is of a Low magnitude, and assumes that the population is present for 12 months. This is considered unlikely and so a Minor adverse impact on the regional wintering population is predicted.
11.7.89 The regional breeding population of lesser black-backed gulls is small, with an estimated 3,520 pairs, which has declined since Mitchell et al. 2004, mainly due to the Orfordness population crash in 2000-01, which was previously around 5,500 pairs alone. If it is assumed that all collisions are on the regional breeding population, then a 32-47% increase in baseline mortality would be predicted as a worst-case. If an average 61% of deaths are during the breeding season when these birds are present, then the magnitude would reduce to Medium-High, and un-mitigated, a Moderate- Major adverse impact on the regional breeding population.
11.7.90 When considering the Alde-Ore Estuary SPA population of 1,603 pairs alone, a Very High magnitude impact is predicted when considering the worst-case scenario, which would reduce to High when only the proportion of deaths during the breeding season is included. The impacts of this are considered in detail in the Information to Inform an Appropriate Assessment in the HRA Report.
Population Viability Analysis- Alde Ore SPA lesser black-backed gulls 11.7.91 With such a high potential magnitude of impact on the Alde-Ore Estuary SPA and regional breeding populations, further detailed population analysis was required to be able to ascertain whether any significant impacts were likely.
11.7.92 A Population Viability Analysis (PVA) model was run to better understand potential long-term impacts of the GWF predicted mortality rates on the Alde-Ore Estuary SPA population. The model was able to capture all the latest productivity data from the Alde-Ore breeding colony and take into account the latest refinements to the collision risk calculations, developed through extensive consultation with the SNCAs, as outlined in the Galloper Wind Farm Collision Risk Modelling Note which was submitted to the JNCC and NE on 29 June 2011 (Table 11.2):
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Temporal period of collision risk. Evidence from the GPS tagging projects within the SPA and at Texel, Netherlands, ringing recoveries from Landguard Bird Observatory data, Wetland Bird Survey (WeBS) core counts (BTO data, June 2011), and studies from other comparable sites (e.g. Leopold et al. 2004; Camphuysen, 2011) were presented to show that SPA birds are likely to be present within the GWF site between March and August only, and so collision rates were limited to these six months. Age structure. The average proportion of adult birds (i.e. potential breeders) recorded each month during GWF boat-based surveys was determined for consideration in the CRM estimates (80-95% adults during the breeding season). Provenance of birds. The proportion of birds recorded foraging within the GWF site that are likely to be from the breeding colonies within the SPA was determined based on regional populations and an assessment of numbers within possible foraging range (a precautionary 5% from other sites). Association with fishing vessels and relocation of a food resource. From boat-based surveys, the level of association of gull records and fishing vessels was recorded. This information was used to determine possible declines in lesser black-backed gull activity post-construction, when fishing activity within the wind farm area, and particularly close to turbines, will be reduced (a decline in at least 15% activity level). 11.7.93 The refinements are precautionary, and where possible, based on empirical evidence taken from on-site (i.e. either the SPA or GWF survey area) or the southern North Sea area. The figures used are backed up with evidence from the scientific literature where available. Annex 4 of Technical Appendix 11.A provides further details of the input parameters of the PVA model.
11.7.94 Based on these outputs of the CRM, used in conjunction with the PVA, it was calculated that up to 245 breeding individuals from the Alde Ore SPA may collide with the turbines each year, using a 98% avoidance rate. This reduces to 122 birds when considering a 99% avoidance rate. It should be noted that this figure is still considered to be a precautionary level of impact on breeding birds, since evidence from Calladine and Harris (1996) and references within, and Camphuysen (2011) suggest that around one third of adults present will be non-breeders in any given year.
11.7.95 Based on evidence from the literature, it has been established that an avoidance rate of at least 99% is a realistic level for many gull species in the offshore environment, see Annex 3 of Technical Appendix 11.A.
11.7.96 Therefore, a total of 122 collisions per annum will increase the baseline mortality of the Alde-Ore SPA breeding population by 38%, which is considered to be a High magnitude. In this worst-case scenario, without
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considering existing SPA management measures that will mitigate population declines, this would result in a significant adverse impact on the SPA population, and as expected, the PVA results (‘Low’ scenario) show an increased decline in the population.
11.7.97 Results of lesser black-backed gull breeding productivity at Havergate Island in 2011 have, however, indicated positive signs of recovery for the colony, suggesting changes to site management under the current EU LIFE+ programme will make a difference to the baseline situation. Here, following production of a predator exclusion plan in 2010, rat bait traps were laid and water levels were raised in the lagoons to reduce the surface area of land suitable for rat habitat. Preliminary results from 2011 suggest that breeding performance of gulls has improved on the previous year, rising from on average 0.35 to 0.50 young per nest. Similar water management measures at the marshes within Orfordness have recently commenced (September-October 2011), and these will aid gull colonies along the outer shingle areas by reducing habitat area suitable for predators (particularly foxes), reducing disturbance levels by humans and dogs, and potentially making the area less susceptible to flooding events. This will increase both adult survival and productivity rates.
11.7.98 Furthermore, consultation with the Alde-Ore SPA landowners (the RSPB and National Trust) undertaken as part of a recent site visit from the GWFL ornithological advisors, detailed in Table 11.2 and Appendix A of the HRA Report, have further informed the development and interpretation of the demographic rates presented in the PVA. In particular, how these relate to the marked interannual variability in colony productivity and the effectiveness of current and potential future management measures.
11.7.99 When these collision figures (122 deaths at a 99% avoidance rate) are entered into the PVA in the Information to inform AA within the HRA Report, and when considering the outcomes of existing site management measures implemented by the Alde-Ore Future for Wildlife Project, it is evident that, based on the likelihood of a future recovery in the SPA population due to reductions in predation and human disturbance (‘Medium’ scenario of the PVA), the SPA population will grow in the long term, despite additional mortality on the SPA population.
Mitigation and residual impact 11.7.100 It is apparent that impacts may occur on breeding colonies within foraging range of the GWF, in particular the Alde-Ore Estuary SPA lesser black- backed gull colonies. The land where the two main colonies are located – at Orfordness and Havergate Island – is owned by the National Trust and the RSPB respectively. Recent population trends have shown that while there has been a substantial decline in numbers at Orfordness, of both lesser black-backed gull and herring gull, numbers have slightly increased at Havergate Island over the same period (RSPB and Landguard Bird Observatory data). This is likely to be due to the higher levels of predation
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and human disturbance at Orfordness (M. Marsh, Landguard Bird Observatory, pers. comm.). As the Havergate colony is on an island, it is protected from land-based predators such as foxes, although rat predation is thought to be a problem, and is subject to a recently funded programme of eradication.
11.7.101 This funding is part of the EU-funded LIFE+ Alde-Ore Future for Wildlife project, which was set up in 2010, in cooperation with the National Trust and RSPB. The main aim of the project is to establish a functional, efficient and sustainable system of ditches, water controls, pumps and sluices to enable long-term water management and control of the coastal lagoons at Havergate Island and the marshes and lagoons at Orfordness. The project also includes the monitoring and protection of vulnerable vegetated shingle habitat on Orfordness, where a lesser black-backed gull colony resides. The project will help the two landowners to manage SPA habitats effectively to enhance biodiversity, protect the sensitive landscape and communicate their work to the general public.
11.7.102 Scientific wildlife and vegetation monitoring commenced in April 2010 on bird numbers, water levels, water quality (salinity) and invertebrates. Vegetation surveys are planned at Orfordness in summer 2011. Management of unauthorised public access to the southern end of Orfordness spit will be reviewed in 2011.
11.7.103 Results from breeding surveys at Orfordness in 2011 showed that in sharp contrast to previous years, gull productivity was much higher, which may be a direct result of site management to date. It is therefore possible that populations of lesser black-backed gull and herring gull recorded during baseline surveys may be underestimates of true populations when construction is scheduled to commence, due to the probability of improved breeding conditions within the SPA, and likely subsequent increases in productivity and immigration to the population.
11.7.104 As the management project is only due to last for five years, it may be possible for GWFL to work in conjunction with the National Trust at Orfordness and the RSPB at Havergate to further fund methods of reversing the downward trend at the former, and maintaining the upward trend at the latter site. Exact action plans would be worked out through consultation with the relevant conservation bodies and SNCBs, but could involve additional funding of predator and human access control, maintenance of food resources nearby the colony, or habitat and vegetation management, in order to increase reproductive success and ultimately population size.
11.7.105 Using the PVA results in the Information to Inform an Appropriate Assessment within the HRA Report, the levels of predicted magnitude for the SPA breeding and larger regional populations prior to SPA management measures are therefore considered to be unlikely. Despite the magnitude of impact being above 1% for the SPA population (see Section 3.6.60), it can
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be shown that the recovery of the population to a favourable conservation status will not be significantly impeded by the additional mortality, and that the SPA’s Conservation Objectives will not be adversely affected. As such a Non-significant impact on the SPA population is predicted, with a Moderate adverse impact on the larger regional breeding population.
Other gulls
11.7.106 Common gull, herring gull, great black-backed gull and kittiwake are considered to be of Low sensitivity to collision risk, with small gulls generally showing evidence of higher avoidance rates (e.g. Everaert and Kuijken, 2007; Everaert, 2008) and a lower proportion of flights at rotor height (Cook et al. in prep) compared to larger gulls. Literature-based evidence from Annex 3 of Technical Appendix 11.A suggests that gull species tend to exhibit avoidances of at least 99%.
11.7.107 None of these species recorded mortality rates that approached significance at an international or national level, except for great black- backed gull where an increase in baseline mortality of up to 1.5% on the breeding, and up to 1.2% of the wintering national populations were predicted. As a species of Medium site-specific sensitivity, this would result in a Low magnitude effect and, therefore, a Minor adverse impact on the national breeding and winter populations.
11.7.108 Although total annual mortality rates of herring gull, great black-backed gull and kittiwake are relatively high compared to the small regional breeding populations, predicted collisions in summer months are very low for each species and so additional mortality will have at worst a Minor adverse impact on breeding colonies, as most of the activity will be from migrating or wintering birds originating further north.
11.7.109 When considering winter populations, it was concluded that the southernmost North Sea figures are the most realistic reference populations, as the large majority of birds present will be migrants. Additional mortality on regional winter kittiwake and great black-backed gull populations are 1.0-1.4% and 1.5-2.0% respectively, which is of Low magnitude. This results in a Minor adverse impact on the regional winter kittiwake and great black-backed gull populations. A Negligible impact on the regional winter common gull and herring gull populations (<1%) is also predicted.
11.7.110 The Alde-Ore Estuary SPA herring gull population is taken to be 672 pairs and the predicted mortality rate would result in an additional mortality rate of 18-36%, assuming all birds are part of the SPA. This magnitude effect is considered very unlikely, since during the summer periods, only 1.1 birds were predicted to collide with turbines in summer, resulting in an increase in mortality rate of 0.8% and a Negligible magnitude effect and a Non- significant impact on the SPA population, see Section 11.3.60.
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Table 11.42 Predicted significance of collision mortality on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Low Medium Negligible / Migratory / Negligible / Low SPA Not skua significant Common National Low Medium Negligible All levels Negligible guillemot
Common Regional Medium Medium Negligible Regional Negligible gull
Fulmar Regional Low Low Negligible All levels Negligible
Gannet Regional Low Low Low Regional / Minor / Not SPA significant Great National Medium High Minor National / Minor Regional black- backed gull
Great International Low Medium Low Migratory / Negligible / SPA Not skua significant Herring National Medium High Negligible / Regional / Negligible / High SPA Not gull significant Kittiwake Regional Medium Medium Minor Regional Minor
Lesser International Medium Very high High / High Regional / Moderate SPA adverse / Not black- significant backed gull
Razorbill National Low Medium Negligible All levels Negligible
Red- International Medium Very High Negligible Regional Minor / Not winter / SPA significant throated diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Barrier Effects 11.7.111 During operation, birds may change their flight path to avoid crossing through a wind farm, with the wind farm effectively acting as a barrier to free
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movement resulting in increased energetic costs of daily movements and migration (DECC 2009; Drewitt and Langston 2006; Masden et al. 2010). The impact as a result of any barrier effect will be species specific; large bulky species with high wing loadings, which have to repeatedly avoid the wind farm, have the potential to be affected most.
11.7.112 Individual turbines or the wind farm as a whole may present a barrier to the movement of birds, restricting or displacing birds from much larger areas. The effect this would have on a population is subtle, and difficult to predict with any certainty. If birds regularly have to fly over or around obstacles or are forced into sub-optimal habitats, this may result in greater energy expenditure. By implication, this will reduce the efficiency with which they accumulate reserves, potentially affecting their survival or breeding success. During the lifetime of the wind farm, there is evidence that some birds may habituate to the presence of turbines, and so this effect may be greatest in the short-term.
11.7.113 Barrier effects are determined by considering (i) the number of birds likely to be flying through the wind farm; and (ii) the extent to which the wind farm will act as a barrier. This is considered on a species-specific basis, based on biological characteristics (for example, wing loading) as well as sensitivity to barrier effects.
11.7.114 The likely worst-case scenario, Table 11.29, considers 140 turbines with a rotor diameter of 120m and a minimum lower rotor tip clearance of 22m above MHWS. It provides the maximum number of structures in the wind farm, to increase the likelihood that birds will avoid individual turbines or the wind farm as a whole. It is assumed that the turbines are spread towards the boundary edge of the turbine array so that the maximum overall area of sea forms a potential barrier of turbines, thereby maximizing the foraging or transit area made unavailable to sensitive species.
11.7.115 As recommended by Maclean et al. (2009), the peak snapshot of birds flying through the site at any one time during boat-based surveys is considered to determine the possible barrier effect.
11.7.116 The energetic consequences of barrier effects are particularly relevant for migratory species, Section 4.252, Technical Appendix 11.A. However, evidence suggests that their deviation from flight paths would occur at hundreds of meters from the turbines which, in the context of their migration range, are unlikely to be significant (Kerlinger and Curry, 2002 and Winkelman, 1992a). Habituation might also occur, reducing the amount of deviation.
11.7.117 Evidence from Horns Rev and Nysted Wind Farms indicated that all bird flocks demonstrated avoidance behaviour from 1.5-2km. There was considerable movement of birds along the periphery of both wind farms, as birds preferentially flew around rather than between the turbines (Petersen et al. 2006). This additional flight period was estimated to represent an
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extra 0.5-0.7% on normal migration costs of eiders migrating through Nysted. Changes in flight direction tended to occur closer to the wind farm by night than day at both sites, but avoidance rates remained high in darkness, when it was also shown birds tend to fly higher. This diurnal pattern was also observed by Krijgsveld et al. (2010) at the OWEZ. Furthermore, at the OWEZ wind farm, bird groups often were seen ‘hesitating’ with flight paths following the edges of the wind farm for some kilometres before entering.
11.7.118 Large gulls flying through the wind farm usually stayed in one corridor, whereas other species such as migrating passerines changed between corridors more often. These data are in contrast to results reported from the Horns Rev and Nysted wind farms in Denmark (Petersen et al. 2006), where birds were largely flying through the corridors.
11.7.119 For each individual, the cost associated with any deviations around turbines increases in proportion to the frequency of passages across the site. Thus, breeding birds making multiple trips will suffer some energetic costs if they avoid travelling through wind farms even if these are relatively low compared to other stochastic variables, such as weather conditions. Species that move through the site on a single occasion during migration are unlikely to bear a measurable cost in most cases, particularly as deviation may begin from a large distance away.
11.7.120 For species predominately on passage, such as skuas, gannet and red- throated diver, the impact of barrier effects could potentially consist of one movement through or around the site area, with an additional deviation if the animal takes the same route through the area during its return migration in the spring. For migrants, the impact of a barrier effect is considered to be of low magnitude. Conversely, local breeders within foraging range of the GWF, such as lesser black-backed gull and herring gull, have the potential to make repeated movements through and within the site, meaning there is the potential for a greater magnitude of impact.
Red-throated diver 11.7.121 Studies suggest that red-throated diver demonstrate a strong avoidance to operational wind farms (Dierschke and Garthe 2006; Petersen et al. 2006). As a reflection of the species’ avoidance of wind farms in general, the sensitivity to barrier effects is rated as High (Table 11.6). Coupled with a Very high conservation value (Table 11.7) the GWF site-specific sensitivity to barrier effects is rated as Very High.
11.7.122 Peak snapshot counts of red-throated diver in flight were in March 2009, with estimates of four birds in Area A and one bird in Area B. Based on Maclean et al.’s (2009) guidance, up to five birds would be expected to be affected by the GWF as a barrier to movement during the migration. Compared to the SPA, regional and national populations, this would result in a Negligible magnitude effect. Red-throated diver range widely across the southern North Sea during the winter months (JNCC/Natural England,
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2010), and are unlikely to make regular foraging trips within the GWF or transit the site to reach important feeding areas. The GWF site may be more important for the species during northwards migration in February in March, with regionally-important numbers passing through the site – however in comparison with the overall length of passage to and from breeding grounds in northern Europe, the extra energy expenditure is likely to be of negligible impact magnitude.
11.7.123 In summary, barrier effects would result in no more than a Minor adverse impact for the regional red-throated population and a Non-significant impact on the Outer Thames SPA population, see Section 11.3.60 and the HRA Report.
Lesser black-backed gull 11.7.124 Lesser black-backed gull may theoretically be susceptible to barrier effects for three reasons: (a) regular foraging trips may take place during the breeding season from the Alde-Ore Estuary SPA across the GWF site; (b) birds migrate through the site to and from summer breeding grounds and wintering areas in southern Europe and north Africa; and (c) birds may move to/from continental Europe and Britain during the non-breeding season.
11.7.125 Snapshot counts resulted in highest numbers in June 2008 – 10 birds in Area A and 101 birds in Areas B and C, resulting in a peak of 111 birds potentially affected by barrier effects. This is considered to be 1.5% of the regional summer population, but less than 1% of the regional winter numbers. Around 3.4% of the current SPA population may be affected.
11.7.126 Compared to other species, the literature suggests that gull are less sensitive to barrier effects. For example, monitoring at operational wind farms in Flanders, revealed the high propensity of gull and tern species to exhibit ‘micro-avoidance’, resulting in a large number of birds that crossed the turbines at close distance (Everaert, 2006). Gulls from the breeding colony at the Port of Zeebrugge (West Dam) undertake multiple daily passages through the wind farm in order to reach offshore foraging areas. This ‘micro-avoidance’ behaviour was also recorded at Blyth Harbour (Lawrence et al. 2007), OWEZ (Krijgsveld et al. 2010) and during surveys on behalf of GWFL in 2011 at Blyth Harbour and Haverigg Wind Farms (RPS, 2011). Gulls showed no apparent barrier effects at operational wind farms, with regular flights between closely-spaced turbines (c.200-300m) recorded (see Annex 3 of Technical Appendix 11.A). It is likely that local gulls have become habituated to their presence over the long term.
11.7.127 There is no evidence to suggest that the GWF intersects the core transit corridor of coastal breeding colonies in Suffolk (in particular the Alde-Ore Estuary SPA) and important offshore foraging areas (DTI, 2006). Indeed, the majority of the site is beyond the likely ‘core’ foraging range of up to 40km from the SPA, Section 4.262-Section 4.64, Technical Appendix 11.A. Lesser black-backed gulls can sometimes forage up to 100km
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(Camphuysen, 1995; Ens et al. 2009), GPS tag data of birds from the Alde- Ore Estuary SPA (Thaxter et al. 2011) and the Dutch Texel colony show that tagged individuals spent a small proportion of their time within the GWF site and adjacent offshore waters.
11.7.128 In the context of their overall flight length, these minor detours around turbines at the GWF are not expected to impact on the fitness of individual’s from the Alde-Ore SPA. Nor are barrier effects likely to impact on migrating birds’ fitness, as any detour will likely result in a negligible increase in flight length.
11.7.129 Although evidence suggests that lesser black-backed gull is of Very Low general sensitivity to barrier effects (Table 11.6), due to the species’ SPA conservation status the GWF site-specific sensitivity is considered to be Medium. An adverse impact on the SPA population is considered unlikely. Regardless of how close the wind farm may be to important gull foraging, roosting or nesting areas, observations from other operational wind farms suggest that gulls are unperturbed by the presence of wind farm arrays, both as a whole and as individual turbines. As the GWF site is not extensively used by breeding birds, there is predicted to be a Minor adverse impact on the regional population, with No significant impact on the SPA population, see Section 11.3.60.
Other gulls 11.7.130 Other gull species (common gull, herring gull, great black-backed gull and kittiwake), are also considered to be of Very Low general sensitivity to barrier effects based on the evidence presented above. During the breeding season, aerial survey results suggest that regionally-breeding common gull. Herring gull and great black-back gull are likely to concentrate in coastal areas as opposed to the offshore waters of the GWF site (DTI, 2006; BERR, 2007a). A significant impact on the Alde-Ore Estuary SPA population of breeding herring gull, which is just within foraging range of the species to the GWF, is considered to be very unlikely since the majority of herring gull are found within the GWF site in winter months only, Section 11.4. The peak snapshot count in summer was five birds, which is less than 1% of the SPA assemblage population.
11.7.131 Kittiwakes are wider ranging than other gull species (frequently foraging up to 70km from the breeding site, utilising a zone of variable width up to 80- 100km away from the coast; Camphuysen et al., 2006), and therefore any barrier effects are also unlikely as the GWF site does not appear to be of particular importance to the species.
11.7.132 In the winter periods, gull species are wider-ranging (although common gull and herring gull distribution is still likely to be predominantly coastal) but the absence of a distinct directionality of movement during this period means that barrier effects are again likely to be of Negligible magnitude at all levels. This would result in a Negligible impact for common gull, herring gull, great black-backed gull and kittiwake. Potential impacts on the
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herring gull SPA assemblage population are considered Not significant (<1% of the population affected), see Section 11.3.60.
Gannet and fulmar 11.7.133 Gannet is rated as being of Very Low general sensitivity to barrier effects, and this results in a Low site-specific sensitivity. Strong avoidance behaviour has been observed at operational wind farms in the Netherlands, although Krijgsveld et al. (2010) reported that gannet changed their flight direction relatively close to the OWEZ wind farm (down to 500m from the boundary of the array site). Compared to their large foraging range (Section 4.271, Technical Appendix 11.A), increases in energy expenditure associated with the close-range avoidance of wind turbines are unlikely to be significant.
11.7.134 If the peak snapshot count of 44 individuals in April 2010 is considered, then these birds potentially affected by a barrier to flight would result in a Negligible magnitude effect on the migratory population (40-60,000 individuals) which is considered to be the most realistic reference population, as most birds recorded were likely to have been on passage at this time.
11.7.135 Fulmars also forage widely (commonly within 100km of the breeding site (Ratcliffe et al., 2000) although breeding individuals have been known to travel up to 400km for food (Dunnet and Ollason, 1982)), and so any barrier effects are again very unlikely.
11.7.136 It is predicted that barrier effects will have a Negligible impact on the regional populations for both species.
Skuas 11.7.137 Arctic skua breed on the northernmost coasts of Europe and is a transequatorial migrant, wintering in southern Africa (BirdLife International, 2004). The species is considered to be of Low sensitivity to barrier effects.
11.7.138 Observations of skua flight behaviour by Krijgsveld et al. (2010) at the OWEZ, noted that all skua sightings showed no evident avoidance behaviour. It should also be noted that, owning to its opportunistic foraging strategies, regular flight patterns for Arctic skua are unlikely – even on migration (Furness, 2002). The GWF site is of some importance for migrating birds in autumn passage only, and although peak counts were below 50 individuals, the conservation sensitivity was considered Very High, thus resulting in a site-specific Medium sensitivity. A peak snapshot count of six birds was recorded on passage in August 2008. This represents <1% of the UK breeding population and SPA populations, Section 4.273 of Technical Appendix 11.A.
11.7.139 When considering the peak total population estimate of 11 birds within the GWF in the same month, numbers still do not reach 1% significance.
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However, as a precaution, a Minor adverse impact is predicted on the flyway population. It follows that effects on the UK SPA population are likely to remain Non significant, see Section 11.3.60.
11.7.140 Great skua is also a long-distance migrant of Low sensitivity to barrier effects (Table 11.6) It is however a species of Very High conservation sensitivity due to the large regional passage volumes (Table 11.22) and possible SPA connectivity. Therefore, the site-specific sensitivity is considered to be Medium. Peak snapshot numbers within the GWF did not reach importance compared to the migratory population (a peak of 7 individuals in September 2008, equating to 0.02%), nor the UK SPA population (0.06%). When the total peak population estimate for the turbine areas is considered (56 birds in September 2008), this represents less than 1% significance at any level. From what is known about the behaviour of the species, any barrier impacts are considered unlikely, with a Minor adverse impact predicted on the passage population and No significant impact on any SPA population, see Section 11.3.60.
Auks 11.7.141 Common guillemot and razorbill are considered to be of High general sensitivity to barrier effects (Table 11.6). The site-specific sensitivity is considered to be High for both species.
11.7.142 No common guillemot or razorbill breed in south-east England and so barrier effects between colonies and foraging areas are likely to be of Negligible magnitude for both species during the summer. Both species disperse widely across the southern North Sea during winter months, rather than being truly migratory (BWPi), and so barrier effects during winter months are also generally likely to be of Negligible magnitude.
11.7.143 When the peak population estimate of common guillemot within the GWF study area is considered (1,705 individuals in February 2009), this does not approach the 1% threshold of the UK SPA population. This is also the case for razorbill where 342 birds were recorded in the same month. No significant impacts are predicted on any SPA population, either within the UK or on the continent, see Section 11.3.60. The population estimates above do represent 4-5% of the migratory common guillemot and razorbill populations in the southern North Sea. Therefore, a Low magnitude impact cannot be discounted. This would result in a worst-case Minor adverse impact on the migratory populations for both species.
11.7.144 A summary of the predicted impacts due to barrier effects on species of principal concern is presented in Table 11.43
Table 11.43 Predicted significance of barrier effects on species of principal concern
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Low Medium Negligible Migratory / Minor / Not SPA significant skua
Common National High High Low Regional Minor winter guillemot
Common Regional Very Low Low Negligible Regional Negligible gull
Fulmar Regional Low Low Negligible Regional Negligible
Gannet Regional Very Low Low Negligible Regional Negligible
Great National Very Low Low Negligible Regional Negligible black- backed gull
Great International Low Medium Negligible Migratory / Minor / Not SPA significant skua
Herring National Very Low Low Negligible Regional / Negligible / SPA Not gull significant Kittiwake Regional Very Low Low Negligible Regional Negligible
Lesser International Very Low Medium Low Regional Minor / Not breeding / significant black- SPA backed gull
Razorbill National High High Low Regional Minor winter Red- International High Very High Negligible Regional Minor / Not winter / SPA significant throated diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
Attraction to lit structures 11.7.145 Birds are often attracted to structures such as oil rigs during the hours of darkness, as they may provide opportunities for extended feeding periods, shelter and resting places or navigation aids for migrating birds. Any benefits of lighting, however, may be outweighed by increased risks of
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collision with oil flares, or in the case of turbines, rotating blades. Lighting on turbines are not expected to be as powerful as oil rig lighting, and so any benefits relating to increased provision of foraging opportunities are likely to be negligible.
11.7.146 The complexity of this issue arises in the fact that disturbance effects of lighting may derive from changes in orientation, disorientation and attraction or repulsion from the altered light environment, which in turn may affect foraging, reproduction, migration, and communication (Longcore and Rich, 2004). Birds may collide with each other or a structure, or become exhausted as a result. Conversely, for unlit turbines at night or during foggy conditions (Trapp, 1998), it is possible that the risk of collision may be greater because moving rotors may not be detectable.
11.7.147 Migrating birds are likely to be particularly susceptible to any adverse effects of lighting. Around two thirds of all bird species migrate during darkness, when collision risk is expected to be higher than during daylight (Hüppop et al. 2006), Section 4.179, Technical Appendix 11.A.
11.7.148 In term of attraction to lit structures, the likely worst-case scenario for the GWF, Table 11.29, would involve 140 turbines and the maximum number of ancillary structures. For maximum visibility, each structure would be fitted with the full lighting requirements for aviation and shipping, with no consideration of directionality.
Potential impacts on all seabird species of principle concern 11.7.149 It is only likely that a significant effect would occur on any species if large numbers of migrants pass through the site at one time. Although it is acknowledged that boat-based surveys are limited in this respect, as no nocturnal passage periods were surveyed, no evidence from baseline surveys at GWF or GGOWF suggested that the GWF site would be important for passerine, geese and wader species which migrate in large numbers compared to most seabirds. As a result, any impacts are considered to be Negligible.
Mitigation and residual impact 11.7.150 Despite being predicted of negligible significance, GWFL will minimise disturbance from lit structures by employing best practice measures such that the lighting of turbines will meet minimum legal requirements, namely as set out in the IALA Recommendation O-117 on ‘The Marking of Offshore Wind Farms’ (further detail available in Chapter 5), for example from the Civil Aviation Authority. Wherever possible and in keeping with the minimum legal requirements, any unnecessary lighting (particularly that directed outwards) will be avoided to minimise the risks of migrating birds becoming attracted to, or disorientated by turbines at night or in poor weather. As a result, lit structures are predicted to have no residual impact to species of principle concern.
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Indirect effects (prey availability and roosting opportunities) 11.7.151 Secondary effects due to operational processes include alteration of the wave action surrounding the turbines which may change prey distribution, or result in the creation of substrate from turbine bases and power cables which may encourage shoaling of prey species or attachment of invertebrates (e.g. molluscs and crustaceans).
11.7.152 The presence of the monopiles and scour protection, and the absence of fisheries, is expected to have the most significant potential impact upon fish species. Noise and vibrations from the turbines and electromagnetic fields from cabling do not seem to have a major impact upon fish and other mobile organisms attracted to the hard bottom substrates for foraging, shelter and protection (Lindeboom et al. 2011).
11.7.153 The hard substrate may increase the opportunities for epifauna to settle and it may provide a substrate, which is more attractive to hard substrate communities than the pre-wind farm seabed. In turn, the naturally occurring species in a softer substrate which may have been present previously in the area will be out-competed and displaced. The establishment of epifauna and flora on the hard substrates may increase the food available to fish, which in turn could lead to an increase in the food available to birds.
11.7.154 The wind farm might affect the fish fauna due to noise and vibrations generated during operation, although it is possible that the fish will become habituated to the noise from the wind turbines. Changes in the water quality and the sedimentary environment caused by the construction and/or operation of the wind-farm may affect the fish population in the area. Sandeels and sprats are very dependent on the availability of suitable sediment, and are particularly sensitive to changes in the content of silt and fine sand (OSPAR Commission, 2004). The physical structure of the foundations and the scour protection may attract some fish species, e.g. because the physical structure provides protection against predation or because it provides protection against the prevalent current and thus saves the fish energy.
11.7.155 A possible reduction in fishing activity within the wind farm could increase prey stocks within and further attract prey and predators. In addition, turbine bases have been shown to create roosting opportunities for foraging birds or migrants (e.g. Leopold et al. 2010), and so there may be small benefits for some species.
11.7.156 The operational subsea transmission cables may result in a warming of the surrounding sediments (OSPAR Commission, 2004). Although the temperature increase will decrease rapidly with vertical and horizontal distance from the cable it may still be high enough to cause abiotic and biotic impacts in the sediments near the sea bottom. Potential impacts include alteration in the endobenthic community including colonisation by alien species and increased risk of botulism in eulittorial areas for wading birds and water birds. In reality, higher levels of heat exchange would only
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occur when the farm is at capacity, and since it is unlikely that the wind farm will run at full capacity 100% of the time, temperature is likely to fluctuate.
Potential impacts on all seabird species of principle concern 11.7.157 At present, although there is limited quantitative evidence of any effects of micro-habitat creation or alteration, the extent of such benefits or adverse impacts for seabirds are likely to be Negligible or Low compared to the size of the GWF site and wider Thames Strategic area. It is possible that the attraction of birds to the base of structures to forage may result in a small increase collision risk, which may cancel out any benefits. Overall, it is predicted that there may be a Negligible impact of all seabird species, with the exception of great skua, lesser black-backed gull and red- throated diver which, owing to their ‘Very High’ site-specific sensitivity, will have a predicted Minor adverse impact at any level.
Table 11.44 Predicted significance of direct disturbance from operational activities on species of principal concern
Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Arctic International Very Low Medium Negligible All levels Negligible skua
Common National Medium High Negligible All levels Negligible guillemot
Common Regional Low Low Negligible All levels Negligible gull
Fulmar Regional Very Low Low Negligible All levels Negligible
Gannet Regional Low Low Negligible All levels Negligible
Great National Low Medium Negligible All levels Negligible black- backed gull
Great International Very Low Medium Negligible All levels Minor adverse skua
Herring National Low Medium Negligible All levels Negligible gull
Kittiwake Regional Low Low Negligible All levels Negligible
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Species Conservation General Site- Magnitude Geographic Predicted value sensitivity specific level of Significance sensitivity impact magnitude
Lesser International Low High Negligible All levels Minor adverse black- backed gull
Razorbill National Medium High Negligible All levels Negligible
Red- International Very High Very High Negligible All levels Minor adverse throated diver
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.8 Potential Impacts during the Decommissioning Phase
11.8.1 As stated in Table 11.29, the final decommissioning proposals will be established prior to construction in agreement with the MMO and relevant SNCAs and stakeholders. Options at the end of the operational lifetime of GWF include removal of all infrastructure, leaving cables in situ but removal of all foundation structures and scour protection (or repowering which would be considered under a separate consenting process). As a precautionary worst case scenario for the purposes of this assessment it is assumed that all GWF infrastructure will be removed as this would lead to the highest number of boat movements, duration of activity and disturbance to the seabed.
Direct disturbance from increased vessel traffic, human presence and machinery operation 11.8.2 A degree of temporary disturbance and displacement is likely to occur throughout the decommissioning phase. The intensity of any impacts are likely to be of a similar scale to those presented for the construction phase in Table 11.31.
11.8.3 Overall, the long term effect of this would be to return the area to its former state and the impact on regional populations of principle concern would be neutral with no impact over the long term.
Impact on subtidal ecology 11.8.4 It has been assumed that decommissioning will include the removal of all offshore structures, GBS foundations will be fully removed and piled foundations will be cut off at or just below the seabed. The removal of this infrastructure will necessitate the use of a heavy lift vessel. It is expected that burial depth will be an important factor in helping to determine the
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appropriate course of action for removal of cables and will therefore be closely monitored throughout the project life-cycle. A typical cable removal programme will include the following
Identify the location where cable removal is required; Removal of cables, feasible methods include: o Pulling the cable out of seabed using a grapnel; o Pulling an under-runner using a steel cable to push the electrical cable from the seabed; or o Jetting the seabed material. Transport cables to an onshore site where they will be processed for reuse/recycling/disposal.
11.8.5 Chapter 12 Marine Intertidal and Subtidal Ecology suggests that the will be similar to those described for the construction phase (physical disturbance, smothering and re-mobilisation of contaminants), although these are likely to be lower in magnitude. Given the low sensitivity of the habitats within the cable array footprint to disturbance and the low magnitude of indirect effects likely to occur on foraging seabirds of principle concern, the significance of the impact overall would be negligible.
11.8.6 In addition there will be the loss of any complex habitats developed on the hard substrate provided by the infrastructure, whilst over time the original habitats lost in the footprint of the infrastructure will redevelop. Overall, the long term effect of this would be to return the area to its former state and the impact would be neutral with no impact on any species of principle concern over the long term.
11.9 Inter-relationships
11.9.1 The inter-relationships between the offshore ornithology and other physical, environmental and human parameters are inherently considered throughout the assessment of impacts (Sections 11.6 and 11.7) as a result of the receptor lead approach to the assessment. For example, offshore ornithology has the potential to be influenced by increases in suspended sediments and changes to the abundance and distribution of prey species as a result of effects on physical processes from the proposed development. The potential impacts as a result of this indirect effect have been discussed within this chapter based on the findings of the assessments made in Chapter 9 Physical Environment, Chapter 10 Marine Water and Sediment Quality and Chapter 12 Marine Intertidal and Subtidal Ecology, Chapter 15 Commercial Fisheries, Chapter 16 Shipping and Navigation and Chapter 18 Military and Civil Aviation.
11.9.2 Similarly any impact on the ornithology from the proposed development has the potential to impact on a number of other receptors, such as fish resource and marine intertidal and subtidal benthic communities. The information provided in this Chapter is used in turn by these relevant
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receptor lead Chapters to establish the potential for and significance of inter-related impacts.
11.9.3 Table 11.45 summarises those inter-relationships that are considered of relevance to offshore ornithology and, identifies where within the ES these relationships have been considered.
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Table 11.45 Offshore ornithology inter-relationships
Inter-relationship Section where addressed Linked Chapter
Construction
Influence of loss of prey Section 11.6 Influencing parameters: resource and or habitat Chapter 12 Marine and Intertidal Ecology and Chapter 13 Fish and Shellfish Resource
Indirect displacement/ Section 11.6 Influencing parameter: disturbance from general Chapter 15 Commercial construction activity Fisheries
Operation
Indirect impacts form the Section 11.7 Influencing parameters: attraction to lit structures Chapter 16 Shipping and Navigation and Chapter 18 Military and Civil Aviation
Indirect impact from prey Section 11.7 Influencing parameters: aggregation effects and Chapter 13 Fish and increased roosting Shellfish Resource opportunities
Decommissioning
Indirect impacts due to loss Section 11.8 Influencing parameters: of benthic prey resource and Chapter 9 Physical changes to seabed habitat Environment and Chapter 12 Marine and Intertidal Ecology
11.9.4 Chapter 29 Assessment of Inter-relationships provides holistic overview of the multiple potential impacts on the project.
11.10 Cumulative Impacts
11.10.1 This CIA takes full account of the COWRIE report “Developing Guidance on Ornithological Cumulative Impact Assessment for Offshore Wind Farm Developers” (King et al. 2009). The process involves a sequence of events, an outline of which is provided below:
Species selection (based on the collected GWF baseline data),
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where selection depends on conservation importance, species whose population within the survey area at any time exceed 1% of the national or regional population as well as species’ sensitivity to offshore wind farm developments (e.g. Garthe and Hüppop 2004, Maclean et al. 2009, Langston 2010); Site selection, which considers all protected sites (SPAs, Ramsar, component SSSIs) within the entire zone of possible influence for each species; Selection of other relevant developments and activities within the predefined zone of possible influence, with the exception of the developments and activities that lack robust baseline information, usually unregulated by an EIA process; Establish the potential effects of each of these developments and activities upon the relevant ornithological features; The significance of cumulative effects is then assessed by summing the impacts from each component development. The exception to summing will be in assessing the cumulative impacts of disturbance and barrier-effects where the impacts accrue in a non- linear manner (King et al. 2009). It is proposed that these are first considered in a qualitative manner making best use of available information. If the cumulative impacts are subsequently thought to be significant, then a more detailed quantitative study may be required; and. The significance of cumulative impacts is initially assessed using the same matrix approach as that routinely used for EIA (Tables 11.6-Table 11.10). This should be supported by detailed discussion of the predicted impact to substantiate the conclusion of a significant or non-significant effect, as recommended by IEEM (2010) and King et al. (2009). Species under consideration 11.10.2 The species that have been included in the CIA are the species of principal concern identified in Section 11.4. Following consultation with the JNCC, NE and RSPB (Table 11.2) it was established that some widely-ranging migratory species that originate from SPAs further north, particularly gannet and skua, may pass through the GWF site and encounter a number of other East coast wind farms along the way. Therefore, for gannet and skua species, additional offshore wind farm projects along the east coast of Britain will be considered, for collision risks and barrier effects only.
Reference populations 11.10.3 For a detailed account of the reference populations under consideration within the CIA, refer to Section 5b of Technical Appendix 11.A.
Wind farm projects under consideration 11.10.4 Following consultation with the JNCC and Natural England (meeting on 6th July 2010), Table 11.2, agreement was reached that projects considered
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would be limited to the Thames Strategic Area, and that Round 3 projects would be excluded from the CIA due to the lack of published data currently available for analysis. During more recent consultation, Table 11.2, it was highlighted by the JNCC that some data were potentially available for the Round 3 East Anglia Offshore Wind Project (ONE). As surveys are on- going for this project, only preliminary collision risk data on lesser black- backed gull were made available from the developer (as of July 2011), in addition to the information available in the EAOne Scoping Report (EAOW, 2010).
11.10.5 Following comments received from the JNCC and Natural England on the Section 42 material, Table 11.2, it was recommended that inclusion of other projects for the CIA should be based on each species’ foraging range, rather than limiting the scope to the Thames Strategic Area.
11.10.6 Depending on foraging range, all, or some of the following Round 1, 2 and 2.5 proposed, consented or operational offshore wind farms within the Thames Strategic Area were considered relevant to the CIA for the species of principal concern:
GGOWF; London Array (phases I and II); Gunfleet Sands I, II and III; Kentish Flats (including extension); and Thanet.
11.10.7 In addition, the following projects were considered for certain relevant species:
East Anglia ONE: available data is limited to the scoping report, although preliminary collision risk results for lesser black-backed gull were made available by the developer; Scroby Sands - although not within the Thames Strategic Area, it partly overlaps with the Outer Thames SPA boundary, and is within foraging range of more wide-ranging species. It has been operational since 2004 and so its effects are incorporated into the baseline survey results for GWF from 2008-10. As a small site some 50km+ north of the GWF, its impacts are expected to be negligible and therefore does not require inclusion in the CIA; and Projects within the Greater Wash Strategic Area and east coast of Britain (Table 61) which are within the foraging range and migratory route for gannet, and also along the migratory flyway for other species such as skuas. Assessment using these sites will be limited to collision risk only.
11.10.8 Details of these projects are presented in Table 11.46.
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Table 11.46 Details of offshore wind farms under consideration in the CIA
Offshore Wind Farm Distance from Number of Status Dates of Construction GWF turbines Galloper - 140 In planning Construction to commence 2014-2016 (nominally 2015). Greater Gabbard 0km 140 Under Construction First foundation was installed in March 2011. Completion by 2012 London Array Phase I c.30km 175 Under Construction First foundation was installed in March 2011. Completion by 2012 London Array Phase II c.25km 166 Approved After 2012 Thanet 37km 100 Operational Operational since May 2010 Gunfleet sands I, II and 41km 48 (+2 for phase Operational Phase I and II operational since March 2010 III III) Kentish Flats 61km 30 Operational Phase 1 operational since June 2005 Kentish Flats extension 61km 51 In planning Extension planned 2013-2014 East Anglia ONE* >4km Not known Concept/early planning 2014 at the earliest Scroby Sands* 71km 30 Operational Operational since December 2004 Westermost Rough* 230km 80 Submitted Approximately 2014 Humber Gateway* 210km 83 Approved Consent granted Feb 2011 –construction estimated to take 2 years. Lincs* 162km 75 Under Construction Construction began in March 2011, due to be completed in 2012 Lynn and Inner 160km 54 Operational Operational since March 2009 Dowsing*
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Offshore Wind Farm Distance from Number of Status Dates of Construction GWF turbines Sheringham Shoal* 133km 88 Under Construction To be completed in 2011 Teeside* 350km 27 Approved To be completed in 2012 Race Bank* 157km 88 Submitted An application for consent was submitted in 2009. Beatrice Demonstrator* c.750km 2 Operational Operational since 2008 Note: *projects outside of the Thames Strategic Area
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11.10.9 As detailed in Sections 11.6-11.8 the main effects for birds of the construction, operation and decommissioning of the proposed GWF lie in the indirect loss of habitat through disturbance, displacement and/or disruption of flight-lines within an area around turbines, and the risk of collision mortality. The development of other wind farms in the region may act cumulatively on any of these aspects.
11.10.10 Cumulative direct loss of habitat due to placement of turbine foundations and other infrastructure is not considered this CIA as it is likely to be very small in relation to the availability of habitat in the Thames Strategic Area and thus of Negligible Significance for all species at a regional scale.
Non-wind farm projects 11.10.11 Regarding non-wind farm projects in the area, guidelines by King et al. (2009) recommend that only regulated projects subject to EIA should be included and that unregulated or unplanned activities such as shipping and fishing are usually integrated into baseline results and not required for consideration. A quantitative approach to assessing the potential impacts of non-wind farm activities was however not possible and a qualitative approach was instead considered. Other activities in the area that may have a direct or indirect impact on birds include the following types of project, identified in the Thames Strategic area by the JNCC/Natural England (2010):
Oil and gas exploration and production; Gas interconnectors; Pipelines for carbon dioxide for storage; Cables; Commercial fisheries; Shipping (including dredging of channels); and Recreation.
Cumulative impacts during construction 11.10.12 The potential cumulative effects of construction and decommissioning are considered to be:
Disturbance and potential displacement due to construction activities including boat traffic and construction noise; and Indirect impacts on local habitat conditions and prey (invertebrates and fish) stocks.
Cumulative direct disturbance effects 11.10.13 The predicted significance level of impact on GWF species of principal concern for disturbance during the construction period was taken from each of the wind farm project’s Environmental Statement (Table 11.47). Where no
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level of significance was specifically given for a particular species, a corresponding value was attributed based on evidence of peak counts recorded during baseline surveys, or when there were comments such as “all other species would be of minor significance”. It should be noted that Table 11.47 presents a scenario if all construction activity were taking take place at the same time. Based on the information in Table 11.46 this will not happen, and so impacts are assessed based on a more realistic worst case scenario.
11.10.14 The effect of disturbance arising from short term increases in vessel traffic and construction activity was assessed as Minor significance for the majority of species at other offshore wind farms, Table 11.47, and thus no further action other than the adoption of best practice (for example, a Site Environmental Management Plan) at individual sites was proposed in the respective ES.
11.10.15 In general, the effects of construction activities may well be smaller than assuming total displacement from the wind farms or their buffer zones. The assessment presented in Section 11.6 indicates that the majority of species which dominate the species assemblage within the Greater Thames, notably the gull, are tolerant to human presence and noisy works.
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Table 11.47 Potential significance of cumulative disturbance (during construction and operation) Greater Gabbard Gabbard Greater I and II London array Gunfleet Sands I & II Flats Kentish Flats Kentish Extension Thanet East Anglia ONE Overall Impact Species Species Galloper
Red-throated Minor Negligible Major Minor Minor n/a Minor n/a Major diver
Fulmar Minor Minor Minor Negligible Minor n/a Minor n/a Minor- moderate
Gannet Minor Minor Minor Negligible Minor n/a Minor n/a Minor- moderate
Great skua Minor Negligible Negligible Negligible Minor n/a Minor n/a Minor
Arctic skua Negligible Negligible Negligible Negligible Minor n/a Minor n/a Minor
Common gull Negligible Negligible Minor Negligible Minor n/a Minor n/a Minor
Lesser black- Minor Minor Minor Negligible Minor n/a Minor n/a Minor- backed gull moderate
Herring gull Minor Minor Minor Negligible Minor n/a Minor n/a Minor-
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Species Species Galloper Gabbard Greater I and II London array Gunfleet Sands I & II Flats Kentish Flats Kentish Extension Thanet East Anglia ONE Overall Impact moderate
Great black- Minor Minor Minor Negligible Minor n/a Minor n/a Minor- backed gull moderate
Kittiwake Minor Minor Minor Negligible Minor n/a Minor n/a Minor- moderate
Common Minor Minor Minor Negligible Minor n/a Minor n/a Minor- guillemot moderate
Razorbill Minor Minor Minor Negligible Minor n/a Minor n/a Minor- moderate
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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Red-throated diver 11.10.16 Table 11.47 suggests that red-throated diver is the only species of principle concern likely to encounter potentially significant levels of cumulative impact due to disturbance. This may be an artefact from the large flock of 4,000 diver recorded in flight during a single survey at London Array (RPS, 2005). This flock was encountered around the time of the spring migration and likely reflects an aggregation of birds from various overwintering locations prior to migration northwards. Therefore, this flock does not necessarily reflect the importance of the wind farm study area and adjacent waters. No other sites, including GWF, were likely to significantly contribute to disturbance effects.
11.10.17 The predicted cumulative Major significance, Table 11.47, is considered very unlikely. As construction effects are likely to be short term in nature, any cumulative impacts will only occur if the construction phases of wind farm projects are coincidental. Using the information in Table 11.46, it is evident that most offshore wind farms in the Thames Strategic Area will be operational by the time that GWF is in-construction, including the first phase of the London Array project (where higher numbers of red-throated diver were recorded). The main possibility of overlapping construction activity is with the planned London Array Phase II extension. There is a lesser possibility that construction of the GWF may coincide with East Anglia ONE.
11.10.18 During periods of adverse weather conditions it is probable that construction activities take place at a lower intensity over the winter months (when the majority of divers are present, Table 11.27). It is therefore considered unlikely that cumulative disturbance of red-throated diver will result in more than a cumulative Minor adverse impact at a regional population level and a non-significant impact at the SPA level, see Section 11.3.60 and the HRA Report.
Other species of principle conservation concern 11.10.19 No additional cumulative impact due to construction disturbance for any other species of principle conservation concern.
Cumulative indirect disturbance impacts 11.10.20 Indirect disturbance impacts may occur through the effect of specific construction activities, e.g. on prey or on habitats, however no potential for significant residual cumulative disturbance impacts on receptors during construction was identified in Chapters 9 (Physical Environment) or Chapter 13 (Fish and Shellfish Ecology). Any impacts on bird behaviour are expected to be short-term only (as detailed in Section 11.6), with limited potential for spatial overlap of impacts caused by GWF construction. Given the above considerations potential for significant impacts is limited, and would be anticipated to be of Negligible to Minor adverse significance at worst, and thus no further action other the adoption of best practice (applied through the Project Environmental Management and Monitoring Plan (EMMP)) at individual sites is required..
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11.10.21 This (Negligible to Minor adverse significance) is in line with the significance of the impact on the majority of species as assessed within other relevant ESs from the Outer Thames Estuary Strategic Area and thus no further action other the adoption of best practice (applied through the Project EMMP) at individual sites is required.
Cumulative impacts during operation 11.10.22 Potentially significant cumulative operational impacts of offshore wind farms on birds are associated with (i) disturbance due to maintenance activities; (ii) displacement of birds around turbines; (iii) barrier effects limiting or preventing free movement; (iv) direct collision of birds with turbines, and (v) indirect cumulative effects on distribution of prey.
Cumulative disturbance due to maintenance activities 11.10.23 In comparison to the construction phase, maintenance activities are likely to be of a lower intensity by involving fewer, smaller boats and shorter visits, reducing the magnitude of any impact. Although the actual levels of maintenance required cannot be accurately predicted, they will be of a longer duration than construction, but likely more localised at any one time. Assuming that each turbine has to be checked at least once a year plus one or two extra visits per turbine to deal with technical problems, Exo et al. (2003) predicted that there may be more or less daily boating activities within a wind farm area.
11.10.24 In general, any maintenance activity impacts are likely to be integrated into the assessment of displacement effects as they will be no greater than the effect caused by the presence of the wind farm (see following section). It may only be in relation to effects outside of the wind farm area (e.g. movements of vessels to and from shore, maintenance along export cable routes) where separate consideration of maintenance activities needs to occur. As disturbance effects will persist over the operational lifetime of the respective wind farms, some overlap in maintenance activity between sites is very likely to occur. In general, other ESs did not evaluate the potential effects of operational disturbance separately, although the significance of the potential impacts at each site is considered based on the significance of impacts during the construction period shown in Table 11.47.
11.10.25 As the spatial magnitude of disturbance effects will likely be lower, the cumulative effect of disturbance from operational disturbance was considered to be Minor adverse cumulative impact for all species of principle concern.
Cumulative displacement and avoidance of turbines 11.10.26 The cumulative displacement effects of WTGs during operation was assessed by estimating the proportion of relevant regional populations found within each offshore wind farm (peak population estimates) and working out the total proportion of birds in the Greater Thames that may be affected by displacement (Table 11.48). Numbers for GWF and GGOWF combined
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were taken from the peak GWF survey area monthly population estimate from 2008-10 boat-based surveys (see Section 11.4).
11.10.27 The potential for significance cumulative displacement impacts was then considered based on the magnitude and general species’ sensitivities to displacement (Table 11.48).
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Table 11.48 Proportions of regional populations within offshore wind farms of the Thames Strategic Area that may be affected by operational displacement
Species Kentish Flats Kentish Flats Extension Kentish + 500m) (wind farm area) (survey Thanet East Anglia ONE results) (preliminary Total Regional population Regional (B/M/W) estimate and Gabbard Greater area) Galloper (survey II Phase I and London array 1km) + (wind farm Gunfleet Sands I & II (wind + 2km) farm
Red-throated diver 7,998 (W) 2.5% 35-85% 3% 0.8% 1% 0.2% 4.6% 47-97%
(204) (2,775- (209) (62) (89) (16) (370 – Zone 5 6,775) aerial surveys)
Fulmar 4,051 (W) 64% 3% 0% n/a 0.05% 1% No 68.0% information (2,619) (130) (0) (2) (33) available
Gannet 40-60,000 2-3% 0.3-0.4% <0.05% n/a <0.005% <0.09% 3-4% 5-7% (M) (1,325) (162) (19) (37) (1,678)
Arctic skua n/a 27 n/a n/a n/a n/a n/a No ? information available
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Species Total Total Regional population Regional (B/M/W) estimate and Gabbard Greater area) Galloper (survey II Phase I and London array 1km) + (wind farm Gunfleet Sands I & II (wind + 2km) farm Flats Kentish Flats Extension Kentish + 500m) (wind farm area) (survey Thanet East Anglia ONE results) (preliminary
Great Skua 27,200 (M) 1% 0.05% 0% n/a 0% 0% No 1% information (313) (15) (0) (0) (0) available
Common gull 20,527 (W) 1% 0.08% 1% n/a 0.06% 1% No 3.1% information (318) (18) (222) (13) (292) available
Lesser black- 11,614 (S) 19% / 8% 10% / 4% 2% / 0.8% n/a <0.07% 1% / 1.3% (S) 33% (S) backed gull 28,788 (W) 0.5% (2,238/2,399) (1,151) (250) (8) (152) 15% (W) (153)
Herring gull 2,362 (S) 1.8% / 2% 42% / 2% 39% / 1% n/a <1% 9% / No 93% (S) 64,172 (W) 0.3% information (85 / 1,083) (1,005) (912) (22) available 6.3% (W) (203)
Great black-backed 25,117 (W) 5% 2% 0.1% n/a 0.01% 0.1% No 7.2% information
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Species Total Total Regional population Regional (B/M/W) estimate and Gabbard Greater area) Galloper (survey II Phase I and London array 1km) + (wind farm Gunfleet Sands I & II (wind + 2km) farm Flats Kentish Flats Extension Kentish + 500m) (wind farm area) (survey Thanet East Anglia ONE results) (preliminary gull available (1,308) (624) (33) (3) (24)
Kittiwake 1,476 (S) 37% / 9% 29% / 1% 16% / 0.8% n/a <0.5% 3% / No 85.5% (S) 30,467 (W) 0.1% information (543 / 2,706) (436) (244) (7) available 11.4% (W) (44)
Common guillemot 29,291 (W) 25% 5% 0.5% n/a 0% 0.7% <19% <50% (193 – all (7,204) (1,581) (162) (0) auks) (5,694 auks – Zone 5 aerial surveys)
Razorbill 6,161 (W) 35% 2% 0% n/a 0% <3% <<92% 40% (193 – all (<132%) (2,187) (139) (0) (0) auks) (5,694 auks – Zone 5 aerial surveys)
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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Red-throated diver 11.10.28 The peak proportion of red-throated diver recorded within offshore wind farms in the Thames Strategic Area initially appears very high – in a worst case the number approaches the entire regional value, Table 11.48. This was mainly due to the peak count of red-throated divers within the London Array Wind Farm plus 1km buffer in February 2004, where a single flock of 4,000 birds was recorded flying through the area, although there was no indication that they were specifically using the boat survey area (other than over-flying it. (RPS, 2005). This unusual case was likely to reflect birds aggregating more closely in larger flocks before their spring migration, and so likely included birds that would not have been present in the Thames Strategic Area during winter months, Section 5.28, Technical Appendix 11.A. This would likely lead to a large overestimate in regional or SPA numbers and actual risks involved. It is noted that London Array Ltd have been working with Henrik Skov (DHI) to undertake a habitat association modelling assessment for red-throated diver within the Greater Thames Estuary which should help to provide greater certainty behind the numbers present at the site. However, the outputs from this work will not be available until November 2011 (Keith Henson, LAL, pers comm.) and therefore, assessments have been based on information that is available at the time of writing.
11.10.29 The migratory Dover strait population of 10-15,000 individuals may be the more realistic worst-case population, with the major peaks at GWF, GGOWF and London Array occurring during February and March. In this case, a range of 24-37% would be potentially affected, excluding the large flock recorded at London Array. If the whole flyway population (75,000 birds) is considered, then around 5% may be affected.
11.10.30 In reality, peak numbers are likely to coincide with birds passing through that are found mainly in the important wintering area for Scandinavian divers in the eastern North Sea along the continental coasts and Helgoland Bight (Stone et al. 1995), as well as further south.
11.10.31 When considering the total area within the Greater Thames potentially lost to displacement, it should be noted that the London Array will account for the large majority of the population, but only a relatively small area. Other Round 2 wind farms close to the shore recorded low numbers and so displacement effects will be low. As outlined previously, the GWF site, and likely the GGOWF site is sub-optimal for the species compared to areas further inshore, and so displacement effects will not be as great as otherwise may have been the case. It is therefore likely that based on cumulative area potentially affected, a Low magnitude impact is predicted. The overall magnitude of cumulative effect based on population affected and area lost is therefore considered to be Medium on the total regional population, and the significance is considered to be a Moderate but tolerable adverse impact, since although numbers are relatively large, the peak populations within the
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area coincides with migratory periods, and so any effects are short-term in nature and this will not affect any individual’s fitness to a significant extent.
11.10.32 Regarding any SPA connectivity, it has been shown that only the Outer Thames SPA population is likely to be affected to any recordable extent by wind farms in the area, although birds that are found in SPAs along the coasts of Belgium and France may pass briefly through the site on migration. Although cumulative numbers are very high compared to the Outer Thames SPA population estimate, the GWF, as explained previously, is unlikely to contribute to a significant extent to the SPA population’s foraging range, with numbers generally very low throughout the winter (peak of 24 birds within the GWF study area in January 2009, which is less than 1% of the SPA population). Birds displaced will therefore be migratory individuals not associated with the SPA. GWF will not significantly contribute to any effects of habitat loss caused by London Array and therefore no significant cumulative effects will occur as a result of the construction of the GWF.
11.10.33 Birds from continental SPAs may pass through the GWF site briefly on migration, but impacts are not considered significant, since the site will be of little importance to these individuals. As presented earlier, the site is likely to be sub-optimal for the species, with widespread similar, or superior habitat in the region. No significant impacts on any SPAs are predicted.
Fulmar 11.10.34 For fulmar, although a High cumulative magnitude of effect was predicted compared to the quoted regional residential winter population (4,051 individuals), this figure is likely to be a large underestimate of actual fulmar numbers, which is a very wide-ranging species, particularly during the winter when peak densities are recorded in the Thames Strategic Area. Total numbers are likely to be somewhere between this estimate and the total flyway population of 10m individuals. No cumulative effects on any breeding population are considered likely, with the southernmost North Sea area providing relatively low densities of birds in the breeding season, and better quality food resources likely to be found closer to northern colonies, for example at the Flamborough Front and Dogger Bank (Stone et al. 1995). Cumulative effects are therefore considered Minor adverse significance at worst.
Gannet 11.10.35 Cumulative gannet displacement was 5-7% of the migratory population, Table 11.48, which was considered to be the most accurate reference population due to the distinct peaks in activity during migration, particularly in autumn, throughout wind farm sites in the Thames Strategic Area and the east coast. Displacement is considered to be Moderate adverse impact. This predicted impact is predicted to be tolerable, as although gannets do avoid wind farms, the cumulative area of habitat loss will be small compared to overall foraging ranges, especially as the species is flexible in its habitat choice (Garthe and Hüppop 2004). The GWF site’s contribution to overall
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displacement area is not considered to be of a significant level compared to other wind farms along the east coast which are closer, or within core foraging ranges of breeding colonies. Any displacement by GWF is likely to be widely-ranging non-breeders or migrants and so will be of negligible impact to such individuals’ fitness levels.
Skuas 11.10.36 For Arctic skua, the regional reference population is unknown. However, in relation to collision mortality, 27 collisions per year represents 0.6% of the national population, which mostly migrate through the North Sea. With evidence in the literature suggesting that skua show no strong avoidance behaviour of wind farms (Krijgsveld et al. 2010), a cumulative Minor adverse impact is predicted. When the UK SPA population is considered, up to 1.7% may be affected, although this is likely to be an overestimate, based on the larger migratory population and proportions of non-breeders, and therefore a Non-significant impact on the UK SPA population is predicted, see Section 11.3.60.
11.10.37 For great skua, 1% of the migratory population was recorded within the GWF and GGOWF combined, with London Array OWF contributing an additional 0.05%, Table 11.48. Great skua was only recorded within the GWF survey area during the autumn migration, Section 11.4, it is therefore considered that the impact magnitude of cumulative displacement is Low in relation to the migratory population. Resulting in a Minor adverse impact on the migratory population. When the UK SPA population is considered as a precaution, Up to 2.6% may be affected assuming all birds are breeding adults. As many of these birds are likely to be non-breeders, part of the larger migratory population and unlikely to be present for any length of time within the GWF study area, it is predicted that cumulative displacement will result in a Non-significant impact on the UK SPA population, see Section 11.3.60.
Lesser black-backed gull 11.10.38 Lesser black-backed gull are of Low sensitivity to displacement- as evidence from studies at operational wind farms suggest they are tolerant of man- made structures (e.g. Leopold et al. 2010; Krijgsveld et al. 2010 and vantage point surveys at GGOWF, Blyth Harbour and Haverigg, 2011).
11.10.39 In total, up to 15-30% of the regional breeding and wintering populations would be affected, Table 11.48. This is seen as very much a worst-case scenario, as compared to the foraging range available of the species, both offshore and onshore, at worst a Low magnitude loss would be shown. The predicted significance was therefore a Minor adverse impact on regional populations due to the species’ evident tolerance of human structures. The cumulative population only forms a fraction of the Alde-Ore Estuary SPA breeding population, Table 11.48, with effects likely being limited to the core
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foraging range (40km) from the SPA. Evidence in Thaxter et al. (2011) and from the RSPB GPS-tagging data showed that, during the breeding season, the foraging range of tagged birds from the Alde-Ore SPA overlapped with GWF, GGOWF and East Anglia ONE. There is little evidence to suggest that any of the Greater Thames wind farm sites are of particular importance to lesser black-backed gull, with many birds foraging along the coast, rivers, inland agricultural areas and also further offshore, refer to the Information to Inform AA within the HRA Report for more details. No significant cumulative impacts on the SPA population are therefore predicted.
Other gull species of principle conservation concern 11.10.40 Similar to other gull species, great black-backed gull are also of Low sensitivity to displacement, and again, due to a Medium magnitude impact, the predicted significance would be at worst a Minor adverse impact on the regional and national populations.
11.10.41 A similar level of impact is predicted for common gull, with low numbers recorded in most sites (Low magnitude).
11.10.42 Although in comparison with the regional summer and winter kittiwake populations the cumulative magnitude of impact is Very high and medium respectively, Table 11.48, it is previously been shown that the population estimates are likely to be a large underestimation of actual numbers present throughout the year in the North Sea. This is particularly the case of the breeding population, which only considers birds within the foraging range of GWF. When all wind farms in the Thames Strategic Area are accounted for, the breeding population will be much larger. A Medium-High magnitude is therefore more likely. The species is wide ranging and has flexible foraging strategies, also shows little avoidance behaviour of wind farms (Krijgsveld et al. 2010), at worst a Moderate impact on the regional population is predicted.
11.10.43 Although a Very High impact magnitude is predicted for the summer herring gull population. This considers birds within the foraging range of GWF only, the Thames Strategic Area breeding population will be much higher. Cumulative effects on the breeding population are most likely to be limited to coastal Round 2 sites, with those such as GWF and GGOWF adding very little impact magnitude since they are beyond the core foraging range (see Section 11.4, Technical Appendix 11.A). Birds present at GWF and GGOWF are likely to be non-breeders, or part of the large migratory population influx from the continent during the winter. Like other gulls, herring gull is clearly tolerant of man-made structures and so significant displacement effects are very unlikely. The impact magnitude is therefore likely to be no worse than Low, resulting in a Minor adverse impact on the regional population.
11.10.44 As mentioned, the GWF and GGOWF site is likely beyond the main foraging range of the Alde-Ore Estuary SPA population, with RSPB 2011 tagging data suggesting that birds are confined to foraging along the coast and inland
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(further details in Information to inform an Appropriate Assessment in the HRA Report), but combined a peak of around 5-6% of the population may be affected. This is considered very unlikely, as birds will be able to continue foraging within the GWF survey area, only potentially being displaced immediately around turbines. Considering the variety of habitats and food sources available to the species, plus the proportions of non-breeders likely present, a Non-significant impact on the Alde-Ore SPA herring gull population is predicted, see Section 11.3.60 and the HRA Report.
Auks 11.10.45 Although a high proportion of common guillemot and razorbill were found within wind farm sites, the species’ sensitivity to displacement is Medium. This would result in a Moderate but tolerable adverse impact as from studies in the southern North Sea, it is apparent that birds range widely in winter and that no particular area is likely to hold great importance to the species. It can therefore be concluded that there will be no significant cumulative displacement effects on common guillemot and razorbill.
Cumulative barrier effects
11.10.46 There is a lack of evidence in the scientific literature as to whether seabird movement is affected by the presence of wind farms, with any impacts being subtle and difficult to measure on individuals’ fitness or reproductive success. It has been shown that some species (for example, diver and scoter) avoid wind farms and take evasive detours, thereby potentially increasing energy expenditure (Petersen et al. 2005; 2006). Although this effect may be negligible when passing around one wind farm, if a series of wind farms are arranged to present a continuous barrier that requires one large detour or many smaller detours, then an individual’s longer trip duration will reduce time spent foraging or roosting, or increase its migration length.
11.10.47 Effects are likely to be greater on birds that regularly commute around a wind farm compared to passage migrants that pass the site once per season. Therefore, for a species such as great skua, although barrier effects are considered to be moderate for the GWF in isolation (see Section 11.7), the proximity and layout of other wind farms in the Thames Strategic Area suggests that there is unlikely to be cumulative barrier effects as a result of the GWF.
11.10.48 The London Array ES predicted a major-moderate impact of barrier effects on red-throated diver, as the site lies within the main foraging range of the species within the Outer Thames Estuary. For all other sites, minor impacts were predicted. Given the relatively low densities of the species recorded within GWF in comparison to other Thames sites, it is not expected that the GWF would have a significant cumulative effect of a barrier to movement as it lies outside of the species’ preferred habitat range and distribution in the Outer Thames Estuary.
11.10.49 Only the GWF and GGOWF reported a possible barrier effect on lesser
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black-backed gull, which is expected since the adjacent wind farms both lie within foraging range of the breeding colonies in the Alde-Ore Estuary SPA on the Suffolk coast. Although the species is highly manoeuvrable and likely to pass between WTGs, it is a possibility that due to the large number of flights during the breeding season, small incremental reductions in a breeding pair’s and therefore juvenile gulls’ fitness may build up. Based on the relative WTG layouts of the two sites however, the GWF would likely account for a negligible increase in flight length, since birds heading to and from the colony would already take evasive action due to the presence of GGOWF turbines. As such, the GWF and GGOWF sites combined may pose a barrier effect to the SPA population, although the GWF site would be considered to significantly increase the levels experienced through the presence of the existing GGOWF site.
11.10.50 The risk to gannet, which may include a proportion of breeding birds which could theoretically make repeat movements through the region due to the large foraging range, might be greater than that of migrants. However, the wide ranging behaviour of this species means that relatively large deviations should not be associated with any significant cost in energetic terms. Consequently no significant cumulative barrier impacts would be anticipated.
Cumulative collision risk 11.10.51 Direct comparison of the collision risks predicted by the wind farms that are operational or in construction in the Thames Strategic Area is problematic due to the differing assumptions made in the calculations used in the different studies, and limited amount of species data presented in ES chapters (see Maclean et al. 2009). Nevertheless, in response to the advice from the SNCAs (Table 11.2), GWFL have undertaken a combined quantitative assessment of the cumulative impacts posed by the GWF in conjunction with the East coast wind farm sites identified in Table 11.49 below.
11.10.52 It should be noted that although this data is presented as a summation in the table below, the interpretation of these predictions, notably for lesser black- backed gull and herring gull, should be augmented with the findings of the tagging data both in terms of overall site usage and SPA connectivity.
11.10.53 For a detailed account of the project details and collision risk assessments provide by the other wind farm projects, refer to Sections 5.63-5.83 of Technical Appendix 11.A.
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Table 11.49 Estimated annual collision rates (realistic avoidance rates) of seabirds at constructed, consented and proposed OWFs for which ES data was obtained Species Species rate Avoidance Galloper Gabbard Greater I and Array London II I & Sands Gunfleet II Flats + Kentish Extension Thanet East Anglia ONE Overall Mortality
Red-throated diver 98% 0.6-1.1 0 n/a <1 1 + 0.1 2 n/a 4.7-5.2
Common gull 99% 1.9-9 n/a n/a <1 n/a + 43 17 n/a 62.9-70.0
Lesser black- 99% 225-330 120 n/a <1 n/a + 2 32 29-33 408-517 backed gull* (374-483)
Herring gull 99% 24-54 n/a n/a <1 n/a + 4 49 n/a 78-108
Great black-backed 99% 38-52 12 n/a <1 n/a + <1 1 n/a 53-67 gull
Kittiwake 99% 46-74 n/a n/a <1 n/a + 2 1 n/a 50-78
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
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11.10.54 For a detailed account of the project details and collision risk assessment s provide by the other wind farm projects, refer to Sections 5.63-5.83 of Technical Appendix 11.A.
Lesser black-backed gull 11.10.55 Evidence from GPS tagging data of lesser black-backed gulls within the SPA (RSPB, Thaxter et al. 2011), HRA Report, suggests that there was temporal and spatial overlap with only some consented Round 1 and 2 wind farms in the Thames Strategic Area which are under construction, as well as the proposed extension sites (including GWF) and the Round 3 East Anglia ONE site, Plot 11.29.
Plot 11.29 Example offshore foraging distribution of lesser black-backed gulls #334 in relation to offshore wind farms, using (a) all data, and (b) ‘foraging’ area (encompassing resting and foraging).
Note: Purple = Round 2 zones, light blue = Extensions and Round 3 zones, blue= Round 1 zones. The example details the percentage of the 95% (total) kernel density estimate (KDE) conducted. Source: Thaxter et al. (2011).
11.10.56 Thaxter et al. (2011) showed that for birds that did forage offshore, the only wind farm sites within 95% Kernel Density Estimate (KDE – used to represent total home range) were GWF, GGOWF, East Anglia ONE and Scroby Sands. The largest overlaps of offshore foraging areas with wind farms were with East Anglia ONE. As Round 1 and Round 2 sites were smaller, these sites generally comprised less than 3% of the KDE for each bird’s offshore foraging range. With the extension sites (the vast majority of records likely to be GWF), again these comprised less than 3% of the KDE of the offshore foraging range.
11.10.57 From the RSPB GPS-tagging data in 2010 and 2011, foraging range of captured birds was comparable to those studied by Thaxter et al. (2011). Only one flight of one bird briefly transacted the corner of London Array, and
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it was not considered of sufficient extent to be included in cumulative CRM results.
11.10.58 At a national level, a cumulative loss of 374-483 birds (when considering GWF, GGOWF and East Anglia ONE) would result in an increase in the mortality rate of the breeding population of 1.7-2.2%, assuming a background mortality of 10%. This would increase the magnitude of impact above that of the GWF alone to Low, which equates to a Minor adverse impact on the national population, and so there will be no additional cumulative effect, and is not significant in terms of the EIA Regulations.
11.10.59 The PVA in the Information to Inform an Appropriate Assessment in the HRA Report shows that cumulative mortality of birds from the Alde-Ore Estuary SPA will not reverse the likely positive growth of the population in the long- term, due to a combination of refinements to the predictions of annual mortality rates on SPA breeding birds outlined previously, and the existing management measures at the SPA. At a 99% avoidance rate, a growth of 1.048 (4.79% per year) is predicted, resulting in a Non-significant impact on the Alde-Ore SPA population.
11.10.60 It should be considered that the SPA holds a smaller (although significant) proportion of the regional breeding population, which is itself made up of lesser black-backed gull colonies within 80km of GWF, Information to Inform an Appropriate Assessment in the HRA Report. GPS tagging data have shown that there is a regular mixing of populations from large colonies in the Netherlands and Belgium during summer months. When the PVA results are accounted for, cumulative effects are therefore more likely to be of a Medium magnitude and therefore a Moderate adverse impact on the regional breeding population is predicted. As the GWF and GGOWF wind farms are adjacent to each other, actual mortality rates would likely be lower than the combined mortality rates provided here, based on the methods of the directional version of the Band et al. (2007) model. As the model does not take into account overlapping rotors, and also assumes that risks are additive (i.e. that a turbine area with 280 turbines will have 280 times the risk of a single turbine) this cumulative impact is likely to overestimate actual collision rates of GWF and GGOWF combined. For a similar reason, a rise to 3-4% additional mortality on the wintering migratory population is also considered to have a Moderate adverse impact on the regional wintering population.
All other species of principle concern 11.10.61 For the other species listed, no cumulative impacts are predicted above the levels of significance presented for GWF alone. Cumulative red-throated diver collision mortality would remain below a 1% additional mortality, resulting in a negligible impact on the regional and SPA populations, and the increase to great black-backed gull and common gull mortality is negligible.
11.10.62 No other sites produced CRM results for kittiwake due to the small peak numbers recorded within, and it follows that cumulative collision risks would
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be non-significant.
11.10.63 Cumulative mortality for herring gull may increase above levels for GWF alone due to figures from Thanet, because of the distance between the two sites, the regional breeding population is likely to be much larger than that used for calculations here, and so significant additional mortality is unlikely. In addition, numbers at Thanet (as well as at GWF) peaked during winter months, indicating that populations comprised mainly migratory birds that do not form part of the regional or SPA populations.
11.10.64 Cumulative gannet, Arctic skua and great skua collision mortality calculations were extended to cover a wider area along the east coast of Britain, due to the species’ extensive foraging ranges. All OWFs were therefore considered, from Beatrice in the Moray Firth to the north, to those in The Wash and the Thames Strategic Areas in south-east England, Table 11.50. In many cases for skuas, CRM calculations were not conducted, and so a more qualitative assessment is required.
Table 11.50 Estimated annual collision rates (98% avoidance rate) of gannet and skuas at constructed, consented and proposed OFWs for which ES data was obtained
Wind Farm Number of Gannet Arctic skua Great skua turbines
Galloper >140 91-112 0-3.6 0-27
Greater Gabbard 140 n/a n/a 0-80
London Array I and II 175 + 166 n/a - -
Gunfleet Sands I, II and III 48 (+2 for n/a - - phase III)
Kentish Flats and extension 30 + 51 6 - -
Thanet 100 2 - -
Westermost Rough 80 1 - -
Scroby Sands 30 n/a n/a n/a
Humber Gateway 83 8 1 -
Lincs 75 9 - -
Lynn and Inner Dowsing 54 <1 - -
Sheringham Shoal 88 31 - -
Teeside 27 12 - -
Race Bank 88 198 - -
Triton Knoll 333 271 4 -
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Wind Farm Number of Gannet Arctic skua Great skua turbines
Dudgeon 168 145 - -
Docking Shoal 83-177 75 7 -
Beatrice Demonstrator 2 4 - -
Total at 98% avoidance 848-869 15.6 53 (107)
Total at 99% avoidance 424-434 7.8 27 (53)
% additional mortality of national breeding 1.0-1.9% 1.0-2.1% 1.1-2.2% pop.
% additional mortality of migratory pop. 3.6-7.2% ? 0.7-1.5%
% additional mortality of flyway pop. 0.5-0.9% <0.04% <0.7-1.5%
Source: RPS, GWF Ornithological Technical Report (September, 2011), Technical Appendix 11.A
11.10.65 Further to the advice from the RSPB, NE and the JNCC (Table 11.2), GWFL have ensured that the cumulative assessment of collision mortality for key migrant and widely-ranging species (namely gannet and skua) captures all East coast wind farm sites within the species’ migratory or maximum foraging range.
Cumulative assessment of collision mortality- Gannet 11.10.66 As a worst-case estimate, the total cumulative annual gannet mortality predicted from sites where CRM figures were available rose from 91-112 birds at GWF alone, to 848-869 for the entire east coast, using 98% avoidance figures. This reduces to 424-434 birds at a more realistic 99% avoidance rate.
11.10.67 For sites with no quantitative CRM information available, a qualitative assessment is required. At London Array, no conventional CRM was undertaken, although the mean count of flying gannets at PCH within the wind farm and the 1km buffer was 3.4 individuals. It was predicted that a significant effect on the regional population (equating to 12 individuals) would result when an avoidance rate of between 99.5% and 99.9% was used. It is therefore unlikely that London Array will add significantly to the cumulative impact of the much larger SPA population, particularly due to its near-shore location being sub-optimal for the species, and resultant low activity levels recorded.
11.10.68 At GGOWF, the peak estimate of gannets within the entire survey area was 276 individuals in December 2005, which is considerably lower than recorded at GWF. It was concluded that the effects of collision risk would be of negligible magnitude, since birds predominantly fly at heights of 10-20m, below rotor height. The site is further inshore than GWF so likely to be less suitable, reflecting the lower numbers recorded.
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11.10.69 At Gunfleet Sands, although the first year post construction monitoring report recorded no gannets flying at PCH within the risk zone, and only eight individuals within the boat survey area between October 2007 and March 2008 (RPS, 2008). Mortality rates are therefore likely to be very low.
11.10.70 In summary, if the annual collision mortality at all east coast wind farm projects was around 850 birds, this would increase the national breeding population mortality above the background rate by 1.9% and above the east coast breeding population mortality by 7.2%, resulting in a Low and Medium impact magnitude respectively. These values are a worst-case prediction and are considered very unlikely. When a more realistic 99% avoidance rate is used, impacts are effectively halved, reducing the magnitudes to Low. This level of impact is considered more likely, based on the species’ clear avoidance of operational wind farms (Petersen et al. 2006; Krijgsveld et al. 2010).
11.10.71 Many birds present are likely to be non-breeding individuals that do not form part of the breeding population - as seen in Figures 33 and 34, during peak migratory periods in autumn, 60-70% of birds identified at GWF were sub- adults. Nelson (1966) found that at the gannetry on Bass Rock, there was a considerable population of adult non-breeders, both as a proportion of birds that do not attempt to nest, and those that were nest or site holders; the latter comprise about a sixth of the adult population. Only 17% of pairs reared young in four successive seasons and 41% in three successive seasons, suggesting intermittent breeding is common. Thus it seems likely that there is a considerable reserve of breeding power in gannetries.
11.10.72 There were approximately 519,000 breeding and non breeding individuals in British and Irish waters during the summer months, based on Seabird 2000 survey results (Mitchell et al. 2004). Breeding numbers since then have increased, and therefore, based on Wetlands International’s (2006) methods of accounting for all gannet individuals in a population (scaling breeding colony counts by 1.5), the current total British population is likely to be around 650,000 individuals, and the east coast population being around 176,000 individuals. During the post breeding period (August onwards) and during the passage periods and winter months the numbers of many seabird species increase considerably in the North Sea area as a whole. This is certainly the case with gannet. It is likely that at least a proportion of the overall passage and wintering gannet populations from various locations in Europe may pass through or use the GWF and other sites (as seen at Dudgeon and Triton Knoll for example), thus elevating the baseline number of birds against which to assess the level of cumulative impact.
11.10.73 Nevertheless, an annual mortality of around 430 birds would result in an additional mortality of 0.7% of the national population and 2.4% of the east coast population. With a currently favourable breeding population within the UK, it is therefore considered that the effects of additional mortality are likely to be a Minor adverse impact on the national breeding population and a
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Moderate but tolerable adverse impact on the east coast breeding population.
11.10.74 Significant cumulative impacts caused by the GWF on the closest colony to east coast wind farm sites at Flamborough Head and Bempton Cliffs SPA are considered unlikely. Evidence from tagged gannet at Bempton Cliffs (Figure 103 in Technical Appendix 11.A from Langston, 2011) suggests that breeding individuals are likely to be confined to waters closer to the colony (50-100km) than the majority of wind farms in the area. Here, only two small wind farms (Westermost Rough and Humber Gateway) are within core foraging range. Similarly, Camphuysen (2011b) showed that most foraging from the Bass Rock colony was within 100km.
11.10.75 As an example, in the Triton Knoll Technical Report (draft version, RPS, 2010), where the site is 85km from Flamborough Head and Bempton Cliffs SPA, it was reported that most gannets pass through the site during the spring and autumn representing a passage population, which could be part of several UK breeding colonies including the Bass Rock and other more northerly East Coast colonies. It was also concluded possible that birds from the west coast of the UK may even be encountered in the North Sea, Appendix D of the HRA Report.
11.10.76 Another site with high predicted mortality rates, Dudgeon, is 150km from the SPA. It was again observed that there was little evidence that birds from the SPA forage here in summer, with most birds being recorded on spring and autumn passage (Dudgeon ES, 2009).
11.10.77 These patterns of gannet usage within the North Sea therefore suggest that in summer months, breeding birds from SPA colonies are likely to be mainly confined within at most 100km of the colony. Westermost Rough and Humber Gateway would be within that distance, as would part of Triton Knoll. As observed at Triton Knoll, birds were not often recorded foraging during summer months, which corresponds with the tracking points of SPA birds, and so SPA mortality is likely to be lower than predicted during CRM calculations, if all deaths are assumed to be SPA birds. In general, offshore wind farm sites reported greatest numbers during migratory periods, when the flyway population swells to 892,000 individuals, and therefore Flamborough Head and Bempton Cliffs SPA birds, and others from east coast Britain breeding colonies will only form a small part of this total of birds on migration down the east coast. Birds present within the GWF site are likely to originate from across most of northern Europe, even on occasion those from colonies in western and southern Britain, as well as Norway and France (the implications of this from a transboundary perspective are discussed in Chapter 31 Transboundary Effects). With such high numbers, few collisions will be birds from the Flamborough Head and Bempton Cliffs SPA, which will likely be present on migration only, (see Appendix D of the HRA Report).
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11.10.78 The Band-based CRM model probably overestimates the number of flights of migratory birds through a site – for example in September 2008, 27 gannet flights were recorded in Area A during snapshots. The CRM predicts that this would result in over 52,000 flights at rotor height during the month within Area A, which equates to over twice the entire Bempton Cliffs population (assuming all birds make one flight through this area). It is therefore unlikely that the GWF will contribute significantly to cumulative mortality on gannets, and no additional cumulative impacts are predicted
11.10.79 In conclusion, the GWF site is just under 300km from the Flamborough Head and Bempton Cliffs SPA and barely within the mean maximum foraging range (BirdLife International, 2010). Therefore, the vast majority of birds found in the GWF that originate from the SPA are only likely to pass through once per season on migration. With the colony showing great expansion since the Seabird 2000 census (up from 2,700 pairs), the true level of significance of cumulative collisions on the Bempton Cliffs SPA population is likely to be Moderate adverse, with GWF contributing very little to these figures.
Skuas 11.10.80 Arctic skua and great skua are present along the east coast of Britain on passage only, with most records occurring during the main autumn southerly migration in August and September.
11.10.81 The majority of other East coast wind farm EIAs did not consider Arctic or great Skua to be of concern in relation to collision mortality. The species’ absence from the collision risk calculations of the other wind farms presented in Table 11.50 is a reflection of the low densities for both species recorded during the baseline surveys. This negated the need for collision modelling to be carried out within the respective ES.
11.10.82 It follows that mortality rates are likely to be very low for both species: even though peak periods of passage may have been missed by surveys, the evidence from all wind farm study areas within the Greater Thames suggests that the area is used only briefly over the entire migration period. Skua may pause in coastal areas whilst on migration, in order to obtain food from small gulls or terns, the data at GWF and GGOWF does not suggest any areas of consistent or sustained kleptoparasitism, Section 11.4.
11.10.83 In general, migration occurs in offshore waters >20km from land (Stone et al., 1995). Therefore most of the Round 1 and 2 sites will not be part of the migratory corridor. This may explain the presence of birds only at further offshore sites such as GWF, GGOWF and Triton Knoll. It is therefore concluded that no site that lacks quantitative mortality estimates will significantly add to the cumulative mortality totals for either species.
11.10.84 When considering a cumulative mortality of 15 Arctic skua per annum, Table 11.50, this would equate to a 2% increase in the baseline mortality of the UK breeding population. It is not clear what proportion this equates to
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when comparing with the migratory population. However, with the Norwegian population being an estimated 9,000 to 14,000 pairs, it is likely that larger numbers will migrate through the North Sea during passage, and that, at worst, a Minor adverse cumulative impact on the national breeding population is predicted. Although SPA populations make up a considerable proportion of the UK population, if the UK and Norwegian populations are included, there would likely be a Non-significant impact on any SPA population, see Section 11.3.60 and Appendix D of the HRA Report
11.10.85 Great skua mortality was not predicted at any other East Coast wind farm site other than the GWF and GGOWF. At GGOWF, a total of 27 strikes per month (converted to 98% avoidance) during the summer was predicted from surveys in 2004/05. With great skuas present for up to three months on migration in this period, this equates to an annual mortality of 80 birds, as no collisions were predicted in spring. Collision rate in 2005/06 was zero. A combined mortality of on average 53 collisions per year means that there would be a 2% increase in baseline mortality, which would result in a Low magnitude on a High overall sensitivity species, and at worst a Minor adverse impact on the national breeding population. When UK SPAs are accounted for (6,262 pairs), this would equate to a 3.2% increase on baseline mortality at worst, assuming all birds killed are part of the SPA breeding population. This scenario is considered highly unlikely and as such, when accounting for the total North Sea migratory population of 27,200 individuals (0.7%-1.5% additional mortality), a Non-significant adverse impact on any SPA population is predicted, see Section 11.3.60.
Interactions with non-wind farm activities 11.10.86 The identified possible non-wind farm activities occurring in the Thames Strategic Area also must be considered when accounting for all possible cumulative effects on species. Such assessments are problematic due to the differences in level of data capture and so often only a qualitative assessment is possible. Much of the information included in this section is taken from the impact assessment of the Outer Thames SPA undertaken by the JNCC/Natural England (2010).
Oil and gas exploration and production 11.10.87 The Outer Thames Estuary area has not been an area of historical petroleum industry activity, with the focus in the southern North Sea being further north between the North Norfolk Sandbanks and the Dogger Bank (MALSF, 2009). The most recent announcement of the 26th Licensing Round for Oil and Gas Exploration (27th October 2010) shows that although 144 licences have been issued (DECC, 2010), this is a reduction in the peaks shown before 2008. There are no current active licence blocks located within or in close proximity to the GWF project and there are no active or abandoned well sites within the GWF site (Chapter 19 Other Human Activities). The nearest active licence block is located over 70km to the north east of GWF. It is likely that oil and gas activities in this area are far enough away from the GWF to reduce the likelihood that these projects could act in-combination on species of principle
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concern that travel between coastal and offshore areas. . As such, there would be no significant cumulative impacts between these licence blocks and the GWF development during construction, operation or decommissioning.
Gas interconnectors and CO2 pipelines 11.10.88 The Bacton-Zeebrugge gas interconnector runs through the southern part of the North Sea. This pipeline is used to export gas to Europe via Belgium and import gas from Europe. Vessels used to maintain the existing gas interconnector in the site, and the proposed pipeline transporting carbon dioxide (CO2) from Kingsnorth power station in Kent for storage in the Hewett gas field to the north Greater Thames, could potentially disturb and displace red-throated divers belonging to the Outer Thames SP or other more sensitive species such as razorbills. However, vessel activity is likely be infrequent and any impacts would be confined to the winter period only, when numbers of these species are highest. It is not possible to accurately determine the level of maintenance required in future years, but no significant cumulative impacts are predicted.
Subsea cables 11.10.89 A number of operational telecommunication cables pass through the southern North Sea. Existing buried cables in the site have a negligible impact on the habitat supporting seabirds, although repair of cable breakages may impact on the seabird population through direct disturbance to the birds during maintenance activity. Any effects are however considered to be localised and short-term, with no significant cumulative impacts predicted for any species.
Shipping (including dredging of channels) 11.10.90 Shipping assessments in preparation for the GGOWF EIA from August to November 2004, suggest that over 90% of vessel tracks in the vicinity of the GGOWF and GWF were commercial shipping (cargo 56%, passenger 13%, tanker 12% and dredger 7%) and 8% were made by fishing vessels (Anatec, 2005, in GGOWFL, 2005). Results showed that the general surrounding area was busy in terms of shipping, in particular to the west of GGOWF. The average number of tracks per day was 115. The GGOWF and GWF sites tend to be avoided by vessels as they avoid the shallow sandbanks in the area.
11.10.91 The GWF site is located close to a number of known marine aggregate extraction areas. Between 1998-2007, 230.19km² of licensed area was surrendered, in comparison only 9.05km² of new area was licensed. During 2007, the total area of seabed that was dredged was 11.93km², (Crown Estate, 2010).
11.10.92 Any shipping activities are unlikely to cause any cumulative impacts on gulls, skuas or gannets due to their low sensitivity to human activity disturbance and flexibility of habitat choice (Garthe and Hüppop, 2004). Dredging activity
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accounts for around 7% of associated vessel movements, and does have the potential to cause disturbance and displacement of red-throated diver and razorbill during peak densities over the winter months, Section 5.117 of Technical Appendix 11.A.
11.10.93 It follows that existing populations of all species are habituated to some extent to the other commercial vessel movements in the area, and so any effects of shipping are incorporated into the GWF baseline survey data. It is expected that any increase in cumulative displacement effects from other human activities would only be potentially significant when there was a concentration of activity in a single year within the main foraging areas for a species. Therefore the cumulative impact of shipping disturbance is considered to be at worst a Minor adverse impact.
Commercial fisheries 11.10.94 A 500m safety zone will be applied for around construction plant and associated acitivity. This will temporarily restrict access to the fishing grounds located within the GWF area. Off the southern half of the Suffolk coast, Essex and Kent, single and multi-rig otter trawlers target Dover sole, as well as cod, whiting, thornback rays, herring, sprat and various other flatfish (JNCC/Natural England, 2010). Fishing vessels with passive gear, such as drift netting, are therefore unlikely to use the area during construction. These usually target pelagic fish / shoals, such as bass, cod and skate. Beam trawling, (for bottom and demersal fish) is also likely to be affected by construction activities, Section 5.112 of Technical Appendix 11.A.
11.10.95 Construction of the GWF cable trench is likely to reduce potting (for shellfish) in the area, which may ease pressure on prey stocks. It is expected that this will resume post construction so any benefits would be short-term. No formal restrictions to fishing vessels once the GWF is operational are planned, apart from a 50m ‘safety zone’ buffer that will be applied for around each structure. An increase in collision risk for vessels may however deter vessels from entering the area. Trawlers, such as beam and otter, may not use the GWF area due to issues with their gear getting tangled / increased likelihood of collision with fixed structures and other vessels. Beam and otter trawls target bottom and demersal fish. A general decrease in fishing activity within the GWF is therefore predicted. Evidence from vantage point surveys at the constructed GGOWF in 2011, Annex 4 of Technical Appendix 11.A, and from OWEZ (Camphuysen, 2011) suggest that gull feeding activity will decrease, or be displaced, if fishing activities cease within the wind farm. Although it is not expected that survival rates will be affected by such conditions.
11.10.96 It should also be considered whether, due to possible displacement of fishing vessels, increased fishing would occur within the Outer Thames SPA. Leading to an increase in the disturbance and displacement of red-throated divers in the areas where there are more productive fisheries that are not
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constantly fished. Information in Chapter 15 Commercial Fisheries suggests that each nationality of fishing fleet has well-defined fishing boundaries within the Gabbard and Galloper areas, and therefore a reduction in activity in the wider area is more likely.
11.10.97 Other species such as gulls and gannets are likely to follow fishing vessels away from the turbine areas, and so a positive impact may result from a lowering of potential collision risk, since a food source (discards) is removed from the area. No significant cumulative impacts are therefore predicted for fishing activities.
Recreation 11.10.98 There is a high level of recreational activity (for example sailing and other water sports) within inshore waters of the Thames Estuary, Chapter 24 Tourism and Recreation. At the current level of activity, there is a low risk that recreational activities will impact on the seabird assemblage, particularly in the offshore waters of the GWF site. No significant cumulative impacts are predicted.
Conclusions of cumulative impacts 11.10.99 There are no predicted significant changes in the levels of impact on any species of principle concern as a result of the cumulative impact assessment, with the possible exception of increases in mortality rates of lesser black- backed gull when considering the GWF and GGOWF combined, and also gannet when considering all east coast sites in combination.
11.10.100 Where a Moderate (or Major) significance of effect has been predicted for the GWF alone, other projects in the area do not contribute notably to the predicted significance level. Conversely, where other projects, either alone or in-combination may have effects that result in a higher level of predicted impact significance, the GWF site is of negligible influence on the overall impact level.
11.11 Transboundary Effects
11.11.1 This Chapter has considered the potential for transboundary effects to occur on offshore ornithology as a result of the construction, operation or decommissioning of the proposed GWF project. In all cases it is concluded that the potential impacts arising, by virtue of the predicted spatial and temporal magnitude of the effects, would not give rise to significant transboundary effects on the environment of another European Economic Area (EEA) member state. A summary of the likely transboundary effects of the proposed GWF is provided in Chapter 31 Transboundary Effects.
11.12 Monitoring
11.12.1 Monitoring will be required where it is conditioned in the Marine Licence. The purpose and objectives of monitoring Round 2.5 projects will need full consideration and consultation with relevant stakeholders prior to
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implementation. Ornithological monitoring will follow methods which enable the comparison of the pre-, during and post-construction relative abundances and distribution for priority species across the wind farm footprint and wider study area. Walker and Judd (2010) reviewed offshore wind farm monitoring data and developed recommendations for project developers that should be relevant to FEPA Licence Conditions. A further detail of the proposed monitoring is provided in Section 6 of Technical Appendix 11.A.
11.12.2 It should be noted that there is an opportunity for GWFL to develop a wider- scale, targeted, monitoring strategy in-combination with the other adjacent wind farms, namely Greater Gabbard (GGOWL) and London Array (LAL). An ornithological monitoring plan will be developed in conjunction with the SNCAs once the project design has been finalised, at least four months prior to the need for any pre-construction monitoring work to commence.
11.13 Summary
11.13.1 Table 11.51 provides a summary of predicted impacts for each species of principle concern, based on their GWF site-specific sensitivity, the predicted magnitude of effect, the subsequent theoretical level of significance (and the modified level if applicable), followed by the rationale behind the decision. The residual significance level is shown based on the predicted impact of any relevant mitigation measures outlined in Section 11.11.
11.13.2 It is evident that from analyses of the results of baseline surveys that the majority of effects of the GWF on species of principal concern will be of Minor or Negligible significance, particularly when relevant mitigation measures are considered. The highest residual impact significance was considered to be of a Moderate-Major level, and this was as a result of the predicted impacts of additional mortality due to collisions of lesser black-backed gulls, at an SPA level. From the results of the PVA carried out specifically to measure long-term trends in the population when additional mortality is considered alongside SPA site management plans (see Information to Inform an Appropriate Assessment in the HRA Report), it was evident that the SPA population is likely to increase in the future, and therefore impacts are considered to be Moderate but tolerable. Mortality rates will also be moderated by the expected reduction in commercial fishing activities in the area of the wind farm.
11.13.3 The cumulative impact assessment in Section 11.10 shows that when considering other projects within the Thames Strategic Area, there will be no significant changes in the predicted level of effects on any species due to the possible cumulative addition of effects. All potentially-significant cumulative effects of displacement and collision risk can be reduced to a moderate but tolerable level when mitigation measures are considered.
11.13.4 It can therefore be concluded that when mitigation measures are implemented to minimise the risk of potentially significant effects on species’ populations, there will be no significant impacts to any species at an
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international, national or regional scale, nor on any Natura 2000 site, caused by the GWF, either alone or in-combination with other projects or activities.
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Table 11.51 Summary of impact predictions and residual significance
Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Red- Construction: Very High Minor adverse Less than 1% of habitat within GWF will None Minor throated Habitat loss be lost adverse Regional and diver (regional and SPA SPA)
Construction: Very high Minor adverse Site is unimportant to species for Project EMMP will minimise Minor Direct feeding, within regional context. Birds disturbance impacts on birds and adverse Regional and disturbance likely only briefly passing through their prey (regional) SPA Not significant (SPA)
Construction: Very High Minor adverse No birds recorded feeding within GWF – Project EMMP applied prior to Minor Indirect most likely passing through on migration offshore construction activities adverse Regional and disturbance so site of low importance commencing (regional and SPA SPA)
Operational: Very High Minor adverse GWF site is relatively unimportant to None Minor species compared with Thames region adverse Displacement Regional and and SPA. It is likely that the GWF buffer (regional) SPA
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity would be able to support any displaced Not birds. 100% displacement is unlikely – significant with most temporary displacement (SPA) concentrated around the immediate GWF and out to, at most, 2km.
Operational: Very High Minor adverse Disturbance due to maintenance None Minor vessels and activities will be of lower adverse Disturbance Regional and extent and intensity than construction (regional) Not SPA disturbance significant (SPA)
Operational: Very High Minor adverse / Only a small number of birds likely to be None Minor Barrier effects not significant affected due to species behaviour adverse (regional) Not Regional and significant SPA (SPA)
Operational: Very high Negligible Risks of migrating birds becoming Wherever possible and in keeping Negligible Attraction to lit attracted to, or disorientated by turbines with legal requirements, lighting (regional and Regional and structures at night or in poor weather will be minimised (particularly SPA) SPA those configurations directed
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity outwards)
Operational: Very High Negligible No birds recorded feeding within GWF – None Minor most likely passing through on migration adverse In-direct Regional and so site of low importance (regional) effects SPA Not significant (SPA)
Operational: Very High Minor adverse / Species generally flies below rotor Wherever possible and in keeping Minor Collision risk not significant height with legal requirements, lighting adverse will be minimised (particularly (regional) Regional and those configurations directed SPA Not outwards) significant (SPA)
Gannet Construction: Low Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
Construction: Low Minor adverse Species is wide ranging Project EMMP to minimise Minor Regional disturbance impacts on birds and adverse Direct
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity disturbance their prey (regional)
Construction: Low Minor adverse Species is wide ranging Project EMMP applied prior to Negligible Regional offshore construction activities (regional) Indirect commencing disturbance
Operation: Low Negligible Benefits or adverse impacts due to Wherever possible and in keeping Negligible Attraction to lit micro-habitat creation or alteration with legal requirements, lighting structures around turbines are likely to be will be minimised (particularly negligible in magnitude compared to those configurations directed overall habitat requirements. outwards)
Operation: Low Minor adverse Species is wide ranging None Minor Displacement Regional adverse (regional)
Operation: Low Negligible Disturbance due to maintenance None Negligible Disturbance vessels and activities will be of lower extent and intensity than construction disturbance
Operation: Low Negligible Species is wide ranging and changes None Negligible flight direction only very close to
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity turbines Barrier effects
Operation: Medium Minor adverse Many birds are likely to be part of flyway Wherever possible and in keeping Minor migratory population rather than with legal requirements, lighting adverse Collision risk Regional and regional winter, or SPA breeding will be minimised (particularly (regional) SPA population those configurations directed Not outwards) significant (SPA)
Fulmar Construction: Low Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
Construction: Low Minor adverse Species is wide ranging and tolerant of Project EMMP to minimise Minor Regional human activities disturbance impacts on birds and adverse Direct their prey (regional) disturbance
Construction: Low Minor adverse Species is wide ranging Project EMMP applied prior to Negligible Regional offshore construction activities (regional) Indirect commencing disturbance
Operation: Low Negligible Predominant flight of fulmar will be Wherever possible and in keeping Negligible
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity below rotor height and be at negligible with legal requirements, lighting Attraction to lit risk of collision or disorientation. will be minimised (particularly structures those configurations directed outwards)
Operation: Low Minor adverse Species is tolerant of wind turbines and None Minor Displacement Regional wide ranging adverse (regional)
Operation: Low Negligible Disturbance due to maintenance None Negligible vessels and activities will be of lower Disturbance extent and intensity than construction disturbance
Operation: Low Negligible Species is likely be able to pass None Negligible between or under turbines; wide Barrier effects ranging
Operation: Low Minor adverse <1% of flights at collision height Wherever possible and in keeping Negligible Regional with legal requirements, lighting (regional) Collision risk will be minimised (particularly those configurations directed
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity outwards)
Arctic skua Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
Construction: Medium Negligible Species recorded briefly on migration in Project EMMP to minimise Negligible low numbers disturbance impacts on birds and Direct their prey disturbance
Construction: Medium Negligible Migratory species that kleptoparasitises Project EMMP applied prior to Negligible other birds. Found in low numbers offshore construction activities Indirect commencing disturbance
Operation: Medium Minor adverse / Migratory species in low numbers None Minor not significant adverse / not Displacement Migratory and significant SPA (migratory and SPA)
Operation: High Minor adverse / Few birds recorded in flight over short Wherever possible and in keeping Minor Attraction to lit not significant period only. Predominant flights below with legal requirements, lighting adverse / not structures rotor height and be at low risk of will be minimised (particularly significant Migratory and
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity SPA collision or disorientation. those configurations directed (migratory outwards) and SPA)
Operation: Medium Negligible Disturbance due to maintenance None Negligible Disturbance vessels and activities will be of lower
extent and intensity than construction disturbance
Operation: Medium Minor adverse / Species is likely be able to pass None Minor not significant between turbines; low numbers adverse / Not Barrier effects Migratory and significant SPA (migratory and SPA)
Operation: High Negligible Few birds recorded in flight over short Wherever possible and in keeping Negligible period only with legal requirements, lighting (migratory) Collision risk Migratory and will be minimised (particularly Not SPA those configurations directed significant outwards) (SPA)
Great skua Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Construction: Medium Minor adverse Although high numbers recorded, this Project EMMP to minimise Minor was only briefly on migration. Species disturbance impacts on birds and adverse Direct National and tolerant of activities. their prey (national) disturbance migratory Not significant (migratory)
Indirect Medium Negligible Migratory species that kleptoparasitises Project EMMP applied prior to Negligible disturbance other birds offshore construction activities commencing
Operation: High Minor adverse/ Few birds recorded in flight over short Wherever possible and in keeping Minor Attraction to lit not significant period only. Predominant flights below with legal requirements, lighting adverse/ not structures rotor height and be at low risk of will be minimised (particularly significant Migratory and collision or disorientation. those configurations directed SPA (migratory outwards) and SPA)
Operation: Medium Minor adverse/ Although high numbers recorded, this None Minor Displacement not significant was only briefly on migration. adverse/ not significant Migratory and
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity SPA (migratory and SPA)
Operation: Medium Negligible Disturbance due to maintenance None Negligible Disturbance vessels and activities will be of lower
extent and intensity than construction disturbance
Operation: Medium Minor adverse Species is likely be able to pass None Minor between turbines; only present briefly adverse Barrier effects National and during long-distance migration (national) SPAs Not significant (SPA)
Operation: High Negligible Many birds are likely to be part of flyway Wherever possible and in keeping Negligible migratory population rather than with legal requirements, lighting (migratory Collision risk Migratory and regional winter population will be minimised (particularly and SPAs) SPAs those configurations directed outwards)
Common Construction: Low Negligible Less than 1% of habitat within GWF will None Negligible
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity gull be lost Habitat loss
Construction: Low Negligible Species is tolerant of human activities Project EMMP to minimise Negligible and mainly coastal numbers recorded. disturbance impacts on birds and Direct their prey disturbance
Construction: Low Minor adverse Species recorded in low numbers, Project EMMP applied prior to Negligible regional mainly coastal offshore construction activities (regional) Indirect commencing disturbance
Operation: Low Negligible Species is tolerant of wind turbines. None Negligible Displacement Found in low numbers in GWF site.
Operation: Low Negligible Low number of birds in flight throughout Wherever possible and in keeping Negligible Attraction to lit year with legal requirements, lighting structures will be minimised (particularly those configurations directed outwards)
Operation: Medium Negligible Disturbance due to maintenance None Negligible Disturbance vessels and activities will be of lower
extent and intensity than construction
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity disturbance
Operation: Low Negligible Species is likely be able to pass None Negligible between turbines due to small size; low Barrier effects numbers recorded
Operation: Low Negligible Low number of birds in flight throughout Wherever possible and in keeping Negligible Regional year with legal requirements, lighting (regional) Collision risk will be minimised (particularly those configurations directed outwards)
Lesser Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible black- be lost Habitat loss backed gull Construction: High Minor adverse Ability of species to tolerate intense Project EMMP to minimise Minor Regional and human activities. Alternative habitat disturbance impacts on birds and adverse Direct SPA available their prey (regional) disturbance Not significant (SPA)
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Construction: Medium Minor adverse Wide ranging and variety of foraging Project EMMP applied prior to Minor strategies to cope with prey disturbance offshore construction activities adverse Indirect Regional and commencing (regional) disturbance SPA Not significant (SPA)
Operation: Medium Minor adverse Species not found on large, nocturnal Wherever possible and in keeping Minor Attraction to lit migration with legal requirements, lighting adverse Regional and structures will be minimised (particularly (regional) SPA those configurations directed Not outwards) significant (SPA)
Operation: High Minor adverse Disturbance due to maintenance None Minor Disturbance vessels and activities will be of lower adverse Regional and extent and intensity than construction (regional) SPA disturbance Not significant (SPA)
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Operation: Medium Minor adverse Species forages widely often in None Minor Displacement association with fishing vessels. GWF adverse Regional and site itself unlikely to be important to (regional) SPA species. Observed to be tolerant of Not human activities. Reduction of fishing significant vessels in GWF will move foraging (SPA) activity but not reduce it.
Operation: Medium Minor adverse Species is likely be able to pass None Minor Regional and between turbines due to high adverse Barrier effects SPA maneuverability (regional)
Not significant (SPA)
Operation: Medium Moderate Reduction of shipping activity will reduce Wherever possible and in keeping Moderate but Regional and food resource and flight activity levels with legal requirements, lighting tolerable Collision risk SPA within wind farm. will be minimised (particularly (regional) those configurations directed SPA management measures are Not outwards) underway to help improve breeding significant
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity conditions and from evidence of higher (SPA) Current management programme productivity in 2011, magnitude of at SPA will help encourage long- impacts based on the 2010 population term shift to favourable condition estimate is unrealistic. for breeding lesser black-backed gull
Herring Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible gull be lost Habitat loss
Construction: Medium Minor adverse Species is tolerant of human activities Project EMMP to minimise Minor disturbance impacts on birds and adverse Direct Regional and their prey (regional) disturbance SPA Not significant (SPA)
Construction: Medium Minor adverse Species is wide ranging, mainly coastal Project EMMP applied prior to Minor offshore construction activities adverse Indirect Regional and commencing (regional and disturbance SPA SPA)
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Operation: Medium Negligible Species is tolerant of wind turbines. None Negligible Found in low numbers in GWF site. (regional) Displacement Regional and SPA Not significant (SPA)
Operation: Medium Negligible Disturbance due to maintenance None Negligible vessels and activities will be of lower (regional) Disturbance Regional and extent and intensity than construction SPA Not disturbance significant (SPA)
Operation: Low Negligible Species not found on large, nocturnal Wherever possible and in keeping Negligible Attraction to lit migration with legal requirements, lighting (regional) Regional and structures will be minimised (particularly SPA Not those configurations directed significant outwards) (SPA)
Operation: Low Negligible Species is likely be able to pass None Negligible between turbines due to high (regional) Barrier effects Regional and
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity SPA maneuverability Not significant (SPA)
Operation: Low Negligible High maneuverability; found in relatively None Negligible low numbers during breeding season (regional) Collision risk Regional and SPA Not significant (SPA)
Great Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible black- be lost Habitat loss backed gull Construction: Medium Minor adverse Species is tolerant of human activities Project EMMP to minimise Minor disturbance impacts on birds and adverse Direct Regional their prey (regional) disturbance
Construction: Medium Minor adverse Species is wide ranging, range of Project EMMP applied prior to Minor feeding strategies offshore construction activities adverse Indirect National and commencing (national and disturbance regional regional)
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Operation: Medium Minor adverse Species is tolerant of wind turbines and None Minor wide ranging adverse Displacement National and (national and regional regional)
Operation: Medium Negligible Disturbance due to maintenance None Negligible vessels and activities will be of lower Disturbance extent and intensity than construction disturbance
Operation: Low Negligible / not Species is likely be able to pass None Negligible not significant between turbines due to high significant Barrier effects maneuverability National and (national and regional regional)
Operation: Low Negligible Species not found on large, nocturnal Wherever possible and in keeping Negligible Attraction to lit migration with legal requirements, lighting structures will be minimised (particularly those configurations directed outwards)
Operation: Low Minor adverse High maneuverability; found in relatively Wherever possible and in keeping Minor
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity low numbers with legal requirements, lighting adverse Collision risk National and will be minimised (particularly (national and regional those configurations directed regional) outwards)
Kittiwake Construction: Low Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
Construction: Low Minor adverse Species is wide ranging and quite Project EMMP to minimise Minor Regional tolerant of human activities disturbance impacts on birds and adverse Direct their prey (regional) disturbance
Construction: Low Minor adverse Species is wide ranging Project EMMP applied prior to Negligible offshore construction activities Indirect commencing disturbance
Operation: Low Minor adverse Species is tolerant of wind turbines and None Minor Displacement wide ranging adverse
Operation: Low Negligible Disturbance due to maintenance None Negligible vessels and activities will be of lower Disturbance extent and intensity than construction
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity disturbance
Operation: Low Negligible Species not found on large, nocturnal Wherever possible and in keeping Negligible migration with legal requirements, lighting Attraction to lit will be minimised (particularly structures those configurations directed outwards)
Barrier effects Low Negligible Species is likely be able to pass None Negligible between turbines due to high maneuverability; wide ranging
Collision risk Low Minor adverse High maneuverability; found in relatively Wherever possible and in keeping Minor Regional low numbers at collision risk heights with legal requirements, lighting adverse will be minimised (particularly (regional) those configurations directed outwards)
Common Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible guillemot be lost Habitat loss
Construction: High Moderate Short-term loss unlikely to be significant Project EMMP to minimise Moderate but as species ranges widely and site not disturbance impacts on birds and tolerable
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity important for species (low feeding rates their prey (regional) Direct Regional recorded) disturbance
Construction: Medium Minor adverse Species is wide-ranging in winter Project EMMP applied prior to Minor months offshore construction activities adverse Indirect Regional commencing (regional) disturbance
Operational High Moderate Species is wide-ranging in winter None Moderate but displacement months tolerable Regional (regional)
Operational: High Negligible Disturbance due to maintenance None Negligible vessels and activities will be of lower Disturbance extent and intensity than construction disturbance
Operation: Medium Negligible Birds likely to avoid vicinity around Wherever possible and in keeping Negligible turbines and will not be at risk of with legal requirements, lighting Attraction to lit attraction. Species predominantly flies will be minimised (particularly structures below rotor height those configurations directed outwards)
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Operation: High Minor adverse Birds range widely but no regular None Minor migratory movement patterns adverse Barrier effects Regional (regional)
Operation: Medium Negligible <1% of flights at collision height Wherever possible and in keeping Negligible with legal requirements, lighting Collision risk will be minimised (particularly those configurations directed outwards)
Razorbill Construction: Medium Negligible Less than 1% of habitat within GWF will None Negligible be lost Habitat loss
Construction: High Moderate Short-term loss unlikely to be significant Project EMMP to minimise Moderate but as species ranges widely and site not disturbance impacts on birds and tolerable Direct Regional important for species (low feeding rates their prey (regional) disturbance recorded)
Construction: Medium Minor adverse Species is wide-ranging in winter Project EMMP applied prior to Minor months offshore construction activities adverse Indirect Regional commencing (regional) disturbance
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity
Operation: High Moderate Species is wide-ranging in winter None Moderate but Displacement months tolerable Regional (regional)
Operation: High Negligible Disturbance due to maintenance None Negligible Disturbance vessels and activities will be of lower extent and intensity than construction disturbance
Operation: Medium Negligible Birds likely to avoid vicinity around Wherever possible and in keeping Negligible Attraction to lit turbines and will not be at risk of with legal requirements, lighting structures attraction. Species predominantly flies will be minimised (particularly below rotor height those configurations directed outwards)
Operation: High Minor adverse Birds range widely but no regular None Minor migratory movement patterns adverse Barrier effects Regional (regional)
Operation: Medium Negligible <1% of flights at collision height Wherever possible and in keeping Negligible with legal requirements, lighting Collision risk will be minimised (particularly
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Species Impact Site- Predicted Rationale Relevant mitigation Residual specific Significance Significance sensitivity those configurations directed outwards)
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