GALLOPER WIND FARM ORNITHOLOGICAL TECHNICAL REPORT
HRA SCREENING
FINAL
28 July 2011
Planning & Development
QUALITY MANAGEMENT
Prepared by: Rafe Dewar
Authorised by: Rhys Bullman
Date: 28 July 2011
Project Number/Document SGP6514 Galloper HRA Report Reference:
DISCLAIMER
The opinions and interpretations presented in this report represent our best technical interpretation of the data made available to us. However, due to the uncertainty inherent in the estimation of all parameters, we cannot, and do not guarantee the accuracy or correctness of any interpretation and we shall not, except in the case of gross or wilful negligence on our part, be liable or responsible for any loss, cost damages or expenses incurred or sustained by anyone resulting from any interpretation made by any of our officers, agents or employees.
Except for the provision of professional services on a fee basis, RPS does not have a commercial arrangement with any other person or company involved in the interests that are the subject of this report.
RPS cannot accept any liability for the correctness, applicability or validity for the information they have provided, or indeed for any consequential costs or losses in this regard. Our efforts have been made on a "best endeavours" basis and no responsibility or liability is warranted or accepted by RPS.
COPYRIGHT © RPS
The material presented in this report is confidential. This report has been prepared for the exclusive use of Galloper Wind Farm Ltd and shall not be distributed or made available to any other company or person without the knowledge and written consent of Galloper Wind Farm Ltd or RPS.
Planning & Development
1 INTRODUCTION
1.1 A Habitat Regulations Assessment (HRA) is required under Council Directive 92/43/EEC on the conservation of natural habitats and of wild flora and fauna (the ‘Habitats Directive’) wherever a project that is not directly connected to, or necessary to the management of a Natura 2000 site1 has the potential to have a significant effect on the qualifying species populations or habitats within the site.
1.2 A HRA comprises sequential steps, the first being ‘Screening’: identifying the likely impacts of the project upon a Natura 2000 site, either alone or in-combination with other plans or projects, and considers whether these impacts are likely to be significant. This step is the precursor to an Appropriate Assessment (AA) which is required where, as a result of screening, it is concluded that a development proposal may have a significant effect on a Natura 2000 site. The AA is conducted by the relevant Competent Authority, based on all information presented, and aims to determine whether any significant impacts identified will have an adverse impact on the Conservation Objectives, and therefore the integrity of the Natura 2000 site.
1.3 The procedures that must be followed when considering developments affecting European sites are specified in Article 6 of the Habitats Directive.
1.4 Under Regulation 61 of the Conservation of Habitats and Species Regulations 20102, a competent authority must undertake an AA where a plan or project:
• Is likely to have a significant effect on a European site (either alone or in combination with other plans or projects); and
• Is not directly connected with, or necessary to, the management of the site.
1.5 If the screening stage clearly identifies that there are not likely to be any significant impacts upon a Natura 2000 site, then an AA will not be required.
1.6 The initial screening step, is focused on the ‘likely significant effect’ (LSE) test. The aim of the LSE test is to determine whether the plan either alone, or in-combination with other plans and projects and activities is likely to result in a significant effect on a Natura 2000 site. The process seeks to understand whether there are any mechanisms for identified impacts arising from the wind farm project to adversely affect a Natura 2000 site (i.e. a cause-effect pathway). The key questions asked are:
° Can significant effects be excluded on the basis of objective information?
1 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.
2 The Conservation of Habitats and Species Regulations 2010 consolidate all the various amendments made to the Conservation (Natural Habitats, &c.) Regulations 1994 in respect of England and Wales. The 1994 Regulations transposed Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora (Habitats Directive) into national law.
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° If not, would the identified effect(s) undermine the Conservation Objectives for the SPA?
1.7 It is a requirement of Article 6(3) of the Habitats Directive that HRA examines the potential for plans and projects to have a significant effect either individually or ‘in combination’ with other projects and activities. The HRA assessment process should take account of reasonably foreseeable impacts (as opposed to every conceivable effect).
1.8 Results of baseline studies, and consultation undertaken on the Galloper Wind Farm (GWF) project to date with the Statutory Nature Conservation Bodies (SNCBs), as well as the formal comments provided by these bodies as part of the GWF Scoping Opinion, indicate that there may be potential for significant effects on the red-throated diver (Gavia stellata) population of the Outer Thames Estuary Special Protection Area (SPA), and on the lesser black-backed gull (Larus fuscus) population of the Alde-Ore Estuary SPA, both alone and/or in-combination with other projects. More recent comments provided by the Joint Nature Conservancy Committee (JNCC) and Natural England on the draft version of this report (letter dated 23 June 2011) also highlight the possibility of cumulative effects of collision risk on northern gannet (Morus bassanus, hereafter referred to as “gannet”) from the nearest colony at Flamborough Head and Bempton Cliffs SPA. This will also be addressed.
1.9 This Report therefore provides the necessary supporting information to enable the Competent Authority (currently the Infrastructure Planning Commission, IPC) and its SNCBs to undertake an HRA screening on the potential for significant effects of the GWF on the qualifying species of Natura 2000 sites.
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2 THE OUTER THAMES AND ALDE-ORE ESTUARY SPAS
a) Outer Thames SPA
2.1 Red-throated diver qualifies under Article 4.1 of the EU Birds Directive (79/409/EEC) for inclusion in the Outer Thames SPA (Figure 1). Over winter the area regularly supports 6,466 individuals, or 38% of the population in Great Britain (peak mean over the period 1989-2006/07) (JNCC SPA citation). The seabed and waters of the Outer Thames area provide an important foraging habitat in the non-breeding season for red-throated diver.
Figure 1: Location of GWF site, Outer Thames and Alde-Ore Estuary SPAs
2.2 The wintering population estimate was generated from aerial survey data commissioned by a number of organisations including the UK Government and a consortium of wind energy companies (DTI, 2006a; BERR, 2007; DECC, 2009). Other data were collected by the JNCC Marine SPA Team, and by the Natural Environmental Research Institute (NERI), Denmark. Data were obtained between the months of October to March in 1988/89, and 2002-2007. Population estimates within the boundary were calculated using spatial analysis to estimate red-throated diver density in 1km grid squares.
2.3 The overriding Conservation Objective of the Outer Thames SPA, as outlined in JNCC/Natural England (2009) is:
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2.4 “Subject to natural change, maintain in favourable condition the internationally important populations of the regularly occurring Birds Directive Annex I species [red-throated diver] and its supporting habitats and prey species [shallow coastal waters and areas in the vicinity of sub-tidal sandbanks]”
2.5 Table 1 further defines favourable condition of the interest feature.
Table 1: Indication of attributes to be used in defining favourable condition for the Outer Thames SPA (from JNCC/Natural England, 2009) Attributes Targets Population size Maintain population on the site subject to natural fluctuations. There should be no permanent decline, only non-significant fluctuation around the mean to account for natural change: where the limits of natural fluctuations are not known (as currently in this case), maintain the population above 50% of that at designation; loss of 50% or more unacceptable Habitat extent Maintain the area of sandbanks in the site subject to natural change: No reduction in extent of sublittoral, shallow (<20m) sandbank habitat. Prey species Maintain the abundance and distribution of red-throated diver prey species subject to natural fluctuations
b) Alde-Ore Estuary SPA
2.6 Lesser black-backed gull qualifies for inclusion in the Alde-Ore Estuary SPA (Figure 1) under Article 4.2 of the EU Birds Directive (79/409/EEC) by supporting a breeding population of European importance of:
2.7 21,700 pairs representing at least 17.5% of the breeding Western Europe/ Mediterranean/ Western Africa population (count as at 1998).
2.8 Since the citation date, the population has suffered a notable decline in numbers, down to 6,000 pairs in 2003 (JNCC Seabird Monitoring Programme data), and most recent counts in 2010 have recorded approximately 1,603 pairs in the Orfordness and Havergate Island colonies combined (Landguard Bird Observatory/RSPB data). The reasons for this decline are not fully understood, but are likely to be due to a combination of increased mammalian predation (M. Marsh, Landguard Bird Observatory pers. comm.), increased human disturbance, reduction in habitat quality, and the reduction of a major inland food source in the free-range pig units in the area, which suffered from outbreaks of swine fever and foot and mouth disease in 2000-01, meaning fewer pigs and thus fewer feeding opportunities for gulls (National Trust, 2010). The creation of these sub-optimal conditions is likely to have caused a reduction in recruitment to the population of young birds from nearby colonies, which would have exacerbated the effects on the breeding population.
2.9 The overriding Conservation Objective relating to qualifying species of the SPA is :
2.10 “Subject to natural change, maintain in favourable condition the habitats for the internationally important populations of regularly occurring migratory bird species, under the Birds Directive, in particular:
• Intertidal mudflats
• Saltmarsh
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• Communities
• Shallow coastal waters”
2.11 The favourable condition, Table 2, supplied by Natural England provides a basis to inform the scope and nature of any AA that may be needed.
Table 2: Indication of attributes to be used in defining favourable condition for the Alde-Ore Estuary SPA Attribute Measure Target Comments Disturbance Reduction or displacement of birds. No significant reduction in numbers or displacement from an established baseline, subject to natural change. Extent of Area (ha) measured once during No decrease in extent from an distribution of reporting cycle. established baseline, subject to habitat natural change. Food Presence and abundance of fish, Presence and abundance of prey Voles, waders, sandeel, availability mammals, birds, ground-surface species should not deviate cod, herring and and aquatic invertebrates measured significantly from an established invertebrates are an periodically, frequency to be baseline, subject to natural important food source for determined. change. lesser black-backed gulls during the breeding season.
c) Flamborough Head and Bempton Cliffs SPA
2.12 Gannet qualifies under Article 4.2 of the EU Birds Directive (79/409/EEC) as part of a seabird assemblage of international importance. During the breeding season, the area regularly supports 305,784 individual seabirds. The SPA holds the only mainland-breeding gannet colony in the UK.
2.13 The most recent count available from JNCC’s Seabird Monitoring Programme database, showed that there were 7,859 occupied sites in 2009 at Bempton Cliffs. The population has shown a steady increase over the last ten years, from 2,552 occupied nests in 1999.
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3 DATA TO INFORM HRA SCREENING FOR RED-THROATED DIVER
3.1 The proposed GWF application site is over 5km from the Outer Thames SPA, although the proposed export cable routes pass through the SPA (Figure 1). In the winter, divers may range widely in the southern North Sea (e.g. DTI, 2006a; BERR, 2007; O’Brien et al., 2008; DECC, 2009), and consequently an unknown proportion of birds that pass through the wind farm areas may be connected to the SPA. It is acknowledged that a lack of information is available on red- throated diver ranging behaviour in the Thames Strategic Area and, therefore, it is not immediately clear whether the impacts of GWF will significantly affect the red-throated diver population of the Outer Thames SPA, nor whether an AA is subsequently required to evaluate the potential effects of the GWF either alone, or in-combination, on the Conservation Objectives of the SPA.
3.2 The following sections therefore present the available information gathered to date on red- throated diver populations, trends and distribution within the GWF, Outer Thames SPA and the wider Thames Strategic Area.
a) Distribution in the Southern North Sea
3.3 Between 13-20% of the biogeographic population of red-throated divers are found within the southernmost North Sea area during a given year, 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.
3.4 An estimated 17,000 red-throated divers winter around Britain, with around 60% of that total off southeast and east Britain, between Flamborough Head and Kent (O’Brien et al. 2008). This population comprises birds from the UK breeding population (the majority from the north of Scotland, particularly Shetland), supplemented by numbers from Scandinavia and a smaller number from Greenland (Maclean et al. 2007). Only data in January and February were used by O’Brien et al. (2008) for estimating the British population, to reflect peak numbers and reduce the amount of birds recorded on passage, as well as double-counting due to the species’ mobility. Actual numbers in the North Sea during winter months are therefore likely to be considerably higher, if migrating birds are considered (the total flyway population is considered to be 75,000 birds – Stienen et al. 2007).
b) Aerial Surveys
3.5 Aerial surveys conducted within the Thames Strategic Area were mainly undertaken during winter months when red-throated divers are present in the area. Three surveys have taken place which cover at least part of the GWF site (DTI, 2006a; BERR, 2007; DECC, 2009). In addition, surveys by WWT Consulting (2009) covered the Round 3 Zone 5 areas to the north of GWF in spring 2009. All followed similar methodology developed in Denmark by the National Environment Research Institute (NERI) (Kahlert et al. 2000; see also Camphuysen et al 2004) and are, therefore, directly comparable.
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3.6 The most comprehensive aerial surveys are by DTI (2006a) and BERR (2007). DTI (2006a) initially found divers at the eastern extremity of the survey extent, after which the survey area was expanded east for the following winter to include blocks TH6 and TH7 in BERR (2007). A summary of all surveys is shown in Table 3 and Figure 2. The GWF site is within block TH3, whereas the Outer Thames SPA is contained within further inshore survey blocks TH1, TH2 and TH4 (Figure 3).
Table 3: Summary of aerial surveys within the Greater Thames area. Densities Survey areas Year calculated DTI (2006a) TH1-TH5 2004/05 Yes
BERR (2007) TH1-TH7 2005/06 Yes
DECC (2009) TH1, GG1-4 2007/08 Yes
WWT Consulting (2009) NS1-NS3 (-NS7) Feb-Apr 2009 No
Survey blocks prefixed TH refer to Round 2 survey blocks, NS refers to Round 3 Zone 5 blocks, and those prefixed GG refer to the GGOWF developments.
Figure 2: Aerial survey sectors within the Thames Strategic Area. Top left: 2004/05 surveys (DTI, 2006); Top right; 2005/06 surveys (BERR, 2007); Bottom left; 2007/08 surveys (DECC, 2009). The GWF is within sectors TH3 and GG1-2 (which is similar in extent to GG3-4, covered in the second survey in 2008 – not shown here).
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Figure 3: GWF in relation to aerial survey sectors. The Greater Gabbard sector is shown in red, with the TH3 sector partially overlapping in extent.
3.7 The species (or species-group where specific identification was not possible), number, behaviour and distance band from aeroplane were recorded during surveys. Only those individuals that were observed clearly were identified to species level; otherwise, birds were identified as being in a species group, e.g. diver (Gavia spp.). The vast majority of divers recorded were considered in DTI (2006a) and BERR (2007) to be red-throated divers as only very small numbers of black- throated divers (Gavia Arctica) were recorded on aerial surveys, even among those birds close to the plane. DECC (2009) however does not make this claim, and so for the GWF EIA, all birds recorded during the 2007/08 surveys are assumed to be red-throated divers.
i. Thames Strategic Area Aerial surveys 2004/05 (DTI, 2006a)
3.8 Aerial surveys in 2004/05 estimated a total red-throated diver population in the Thames Strategic Area of 5,634 individuals (DTI, 2006a). Divers were found widely distributed throughout most of the aerial survey area. Although some concentrations appeared to be found close to shore and around the mouths of estuaries in some survey blocks, birds were consistently encountered over 40km from shore, albeit in low densities. Very few divers were recorded in and around the GWF study area east of the GGOWF, those seen being with the northern Inner Gabbard turbine area of the GGOWF (Figure 4).
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Figure 4: Summed red-throated diver distribution in winter 2004/2005, showing GGOWF boundaries. GWF is directly to the east. From Banks et al. (2006), adapted from DTI (2006a).
3.9 Divers were present in large numbers from survey Period 2 (November-December) onwards in the Thames, with consistently around 1,000 birds (combining all species and unidentified birds). The vast majority are likely to have been red-throated divers. The number of divers increased in the inner part of the survey area (TH1 and TH2) and decreased in the outer survey area (TH4 and TH5) through Periods 2-4 (mid-late winter).
3.10 The highest densities were in mid channel in the outer part of the Thames 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 in the waters between Kent and Essex.
3.11 In TH3 (the block that overlaps with GWF), numbers of divers peaked at 22 birds during Period 3 (January-February), which is low compared to those further inshore at TH1, TH2 and TH4, where 429, 172 and 295 birds were recorded respectively. Distance estimates by Banks et al. (2006) produced a peak population of 98 birds in TH3 in Period 3 (January-February) of 2004-05, which is around 1.5% of the SPA population. This equates to a peak density of 0.1 birds per km2. Estimates for TH1 and TH4 were 2,194 and 1,167 birds respectively in Period 3 (18 and 34% of the SPA population respectively).
ii. Thames Strategic Area Aerial surveys 2005/06 (BERR, 2007)
3.12 Aerial surveys in 2005/06 estimated a total red-throated diver population in the Thames Strategic Area of 7,998 individuals (BERR, 2007). Again, highest concentrations of divers occurred off the mouths of estuaries and in inshore areas. Low densities of birds were encountered a long way from shore, and extended up to the outer limits of the survey areas in the Thames Strategic Area. Small numbers of divers were recorded in the Thames Strategic Area in early winter, rising
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rapidly through mid winter then stabilising with almost identical counts in Periods 3 and 4 of around 1,360. The increase in numbers during the latter two Periods was partially due to increased coverage (TH6 and TH7) during this time, though numbers increased substantially in TH2.
3.13 The highest concentrations of divers in the Thames Strategic Area occurred in mid channel, often up to 30km offshore and in inshore areas off Great Yarmouth. Smaller numbers were found widely distributed throughout the area, extending to the outer limits of the survey area. Birds often occurred in flocks of more than ten individuals, near channels and sandbanks, mid way between Kent and Essex.
3.14 Although the main concentrations were in roughly the same areas throughout the winter, there was some variation in distribution between months. In mid to late winter fewer birds were found in the south and in offshore parts of the north of the survey area, as birds appeared to concentrate in central areas, and move inshore in the north.
3.15 In TH3, raw count numbers peaked at 114 birds in Period 4, rising from 86 birds in Period 3. This was low compared to other blocks, e.g. 403 in TH2, 396 in TH1 and 251 in TH4, which are more inshore than TH3. TH1 and TH2 held an estimated 4,167 birds during period 3, using Distance estimates, compared to a peak of 729 birds (density of 0.69 birds per km2) in TH3 during Period 4 (February-March) of 2005-06 (Banks et al. 2006), which is 11.2% of the SPA population. In comparison, TH1 and TH2 held 64% of the SPA population during this period, and densities reached 2 birds per km2.
iii. Thames Strategic Area Aerial surveys 2007/08 (DECC, 2009)
3.16 Aerial surveys were undertaken in 2007-08 in the Greater Gabbard Area (GG1-4) and further inshore in the Thames (TH1) (DECC, 2009). Surveys in the Greater Gabbard Area were conducted during Periods 3 and 4 (mid-late winter, January to March) which coincide with the main red-throated diver activity period. Moderate numbers of divers were recorded in the north of the area (Figure 5). Surveys in the Thames (TH1) were conducted during all winter periods. TH1 held comparatively large numbers of divers distributed over shallow intertidal sand banks around the estuary mouth.
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Figure 5: Relative density of divers (Gavia spp.) recorded in the TH1 & Greater Gabbard areas during aerial surveys, 2007/08 in Period 3 (left) and Period 4 (right). Source: DECC (2009).
3.17 A total of 41, 635, 346 and 127 divers were recorded in TH1 during Periods 1-4 (early to late winter, late October to March) respectively. In all periods the diver records were widely distributed through the Thames Estuary. There was an apparent pattern of distribution, particularly in Periods 2 and 3, with the south-west to north-east trending bathymetric features of the Thames Estuary (Figure 6).
Figure 6: Bathymetry of the GWF and GGOWF sites
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3.18 The Greater Gabbard blocks were surveyed in Periods 3 and 4 in the winter, with 51 (GG1 and GG2 combined) and 124 (GG3 and GG4 combined) divers recorded respectively. In Period 3 these were mostly located in the north and west of the area, between Kentish Knock and The Galloper sandbank, and north of the Inner Gabbard sandbank (Figure 6). In Period 4 most observations were in an area around the Outer Gabbard sandbank and stretching north and west. The 2km grid cell in Period 3, and the two in Period 4, showing relative densities over five birds per km in Figure 7 respectively are due to only partial coverage of these cells. These cells only contained three or fewer divers each.
Figure 7: GWF boat-based survey transects 2008-10
3.19 Distance sampling estimated 1,714 individuals (1,238-2,373 confidence interval) for the combined TH and GG areas in Period 3, and 1,469 individuals (1,125-1,867) in Period 4 (DECC, 2009).
3.20 For the purposes of the GWF EIA, Distance calculations carried out on GG1-4 survey blocks estimated a peak population of 253 divers (all species, but considered to be all red-throated divers) in March, which equates to 3.9% of the SPA population, and a density of 0.11 birds per km2. Numbers were lower during the first survey in February, with an estimated 152 birds (2.3% of SPA population and a density of 0.07 birds per km2).
3.21 WWT Consulting (2009) surveyed the Round 3 Zone 5 areas to the north of GWF in March 2009. A peak number of 121 birds were recorded in both survey blocks NS1 and NS3, with 71 birds in NS1. Although the GWF site was not sampled, the figures do provide a recent snapshot of numbers of divers within the nearby Zone 5.
3.22 A summary of Distance-calculated estimates for each aerial survey, and survey block (where presented) is shown in Table 4.
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Table 4: Estimates of diver numbers for each period for survey blocks holding significant numbers of divers. Areas with insufficient data to allow estimates to be calculated were excluded. Source: DTI (2006a), Banks et al. (2006), BERR (2007), DECC (2009). Lower Confidence Upper Confidence % of SPA Year Period Block Estimate Interval Interval population 2007/8 2 TH1 2129 1524 2909 32.9%
2004/5 3 TH1 2194 1723 2652 33.9%
2005/6 3 TH1 1913 1562 2341 29.6%
2005/6 4 TH1 1724 580 2469 26.7%
2005/6 3 TH2 2254 1301 3907 34.9%
2004/5 4 TH2 1196 510 2141 18.5%
2005/6 4 TH2 1441 512 2076 22.3%
2004/5 1 TH3 0 0 0 0.0%
2004/5 2 TH3 14 5 41 0.2%
2004/5 3 TH3 101 58 175 1.6%
2004/5 4 TH3 96 50 188 1.5%
2005/6 1 TH3 20 2 63 0.3%
2005/6 2 TH3 40 19 87 0.6%
2005/6 3 TH3 582 466 728 9.0%
2005/6 4 TH3 729 593 895 11.3%
2004/5 2 TH4 1779 1068 2374 27.5%
2004/5 3 TH4 1167 702 1716 18.0%
2004/5 1 TH5 642 476 807 9.9%
2004/5 2 TH5 840 552 1279 13.0%
2005/6 1 TH6 292 178 430 4.5%
2007/8 1 TH & GG 268 177 355 4.1%
2007/8 3 TH & GG 1714 1238 2373 26.5%
2007/8 4 TH & GG 1469 1125 1867 22.7%
2007/8 3 GG 1-2 152* 77 302 2.4%
2007/8 4 GG 3-4 253* 88 732 3.9% *estimates calculated by RPS for the purposes of the GWF EIA.
3.23 Tables 5 and 6 show Banks et al.’s (2006) estimated densities of red-throated diver during the winter aerial survey periods in 2004/05 and 2005/06, within each survey sector. The results show that survey sectors that are closer to the coast, particularly TH1 within the mouth of the Thames Estuary, hold highest numbers of red-throated diver. The outer sectors, particularly TH3
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and TH7 hold relatively low densities of individuals. Sector TH3 shows a clear increase in densities in Periods 3 and 4 (February-March) which correspond with boat-based survey results below.
Table 5: Estimates of red-throated diver densities within each survey block, from 2004/05 aerial surveys in the Thames Strategic Area TH1 TH2 TH3 TH4 TH5 Period 1 0.05 0.07 0.00 0.06 n/s Period 2 1.05 0.54 0.01 1.56 0.66 Period 3 1.56 0.64 0.10 1.09 0.39 Period 4 1.24 1.08 0.09 0.45 0.11 Average 0.97 0.58 0.05 0.79 0.39 From Banks et al. (2006). Figures highlighted in red exceed the 0.62 birds per km2 threshold for Outer Thames SPA inclusion
Table 6: Estimates of red-throated diver densities within each survey block, from 2005/06 aerial surveys in the Thames Strategic Area TH1 TH2 TH3 TH6 TH7 Period 1 0.00 0.04 0.02 0.29 0.02 Period 2 2.16 0.35 0.04 0.46 0.74 Period 3 2.14 2.36 0.55 0.15 0.28 Period 4 2.08 1.98 0.69 0.28 0.07 Average 1.59 1.18 0.32 0.30 0.28 From Banks et al. (2006). Figures highlighted in red exceed the 0.62 birds per km2 threshold for Outer Thames SPA inclusion
c) Boat-based surveys
3.24 The following boat-based survey data have been used to inform the HRA screening assessment:
• 2004-06 surveys conducted to inform the EIA for the GGOWF. It should be noted that the transect survey area only partially overlapped with the GWF site (Figure 7);
• June 2008 to May 2009 preconstruction survey year 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, although construction activity had commenced in the former site at the end of August 2009.
3.25 Tables 7a and 7b and Figure 8 provide a summary of the population estimates for the constituent survey areas in each boat-based survey during 2008-10. It should be noted that some of the constituent survey areas’ sample sizes were relatively low, and so caution should be expressed while interpreting these population estimates. Distance sampling was conducted separately for the entire survey area, and that is why occasionally totals for constituent parts add up to more than the population estimate for this larger area.
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Figure 8: Red-throated diver population estimates from boat-based surveys within the GWF survey area in 2008/09 and 2009/10, showing 1% SPA population (64 individuals). Although the majority of surveys were conducted in regular monthly intervals, some months were missed due to poor weather conditions. In these cases, catch-up surveys were conducted during the first week of the following month. To allow direct comparisons between years, these surveys have been allocated the month of the originally-planned survey dates, e.g. the survey conducted in early November 2008 has been allocated as the October 2008 survey. No survey was conducted which equates to the month of November 2009.
Tables 7a and 7b: Monthly red-throated diver population estimates for GWF survey area and component parts
2008-09 Area Jun Jul Aug Sep Nov (1) Nov (2) Jan (1) Jan (2) Feb Mar Apr May Area A 0 0 0 0 0 0 0 0 0 21 0 0 0-4km buffer 0 0 0 0 7 5 11 5 16 11 0 0 Area B 0 0 0 0 0 0 0 0 0 60 0 0 0-4km buffer 0 0 0 0 0 0 13 0 20 20 7 0 Total Survey Area 0 0 0 0 6 52 58 15 204 70 5 0
2009-10 Area Jun Jul Aug Sep Oct Nov Dec Feb (1) Feb (2) Mar Apr May Area A 0 0 0 0 0 n/a 0 8 1 0 0 0 0-4km buffer 0 0 0 1 0 n/a 0 13 6 15 0 0 Area B 0 0 0 0 0 n/a 0 0 22 18 0 0 0-4km buffer 0 0 0 0 0 n/a 0 7 29 32 2 0 Total Survey Area 0 0 0 1 12 n/a 0 33 43 71 2 0 Blue shading denotes >1% SPA population
3.26 As expected, most red-throated divers in the survey area were found in winter months. In February and March 2009 the estimated numbers of red-throated divers within the entire survey area exceeded 1% of the SPA population (up to 3.1% of the SPA population in February,
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although numbers within the GWF turbine areas A and B were considerably lower). During March 2009, numbers within GWF turbine areas A and B exceeded 1% of the SPA population. A peak density estimate of 0.18 birds per km2 was recorded in February 2009 in the whole survey area. Numbers in 2009/10 were lower, with a peak density of 0.06 birds per km2 in March 2009. The peak population estimate for the entire survey area was 71 individuals in March (1.1% of the SPA population), and may have reached 1% when considering the two turbine areas plus 4km buffers.
3.27 In general, during GGOWF surveys in 2004-06, red-throated diver numbers were lower than in 2008/09 surveys, but similar to those in 2009/10. Corrected population estimates of the entire GGOWF study area (BTO, 2006) peaked at 77 birds in March 2004 and 120 birds in January 2006 (1.1% and 1.8% of the SPA population respectively). Highest numbers within the GGOWF site were again in February and March.
d) Distribution and behaviour
3.28 The GWF site is around 27km from the shore at its closest point, which is outside the main distribution area of red-throated divers recorded during aerial surveys in southeast England, established as being mainly 10-20km from the shore (e.g. DTI, 2006a; DECC, 2009; Webb et al. 2009). This suggests that the GWF site is sub-optimal habitat for the species. Evidence from the aerial surveys above confirms that the GWF and GGOWF sites are relatively unimportant to the species, compared with areas further inshore in the Thames Estuary. Figures 9 and 10 show there are no obvious regular focal areas of activity within the study area, but birds are more prominent in western waters nearer the coast, and perhaps this is distribution is accentuated by the presence of shallower sandbanks within the GGOWF (Figure 6). The GWF turbine areas appear to be relatively unimportant for the species compared to the GGOWF and surrounding survey area further inshore as a result. Population estimates from boat-based surveys in 2008- 10 suggest that for the majority of the winter the GWF survey area holds smallish numbers of divers (<1% of the SPA population), except during the main spring migratory period in February and March when birds are more widespread. It is therefore more likely that at least some of these birds do not overwinter in the Outer Thames SPA, but in areas further south.
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Figure 9: Red-throated diver boat survey counts, 2008/09
Figure 10: Red-throated diver boat survey counts, 2009/10
3.29 Although relatively unimportant for the species, it is evident that red-throated divers do regularly use the GWF site. Of the 111 birds recorded in transect during boat-based surveys in 2008/09,
Planning & Development 17
103 were recorded on the sea. Of these birds, only 11 remained on the water throughout, and it is considered likely that the vast majority of the remainder were flushed by the survey vessel, given observed behaviour. Of the 47 birds recorded in transect in 2009/10, only 4 remained on the water throughout. Collision risk modelling may therefore overestimate numbers in flight due to the reaction of birds to the survey vessel, although this may be balanced by the under recording of birds that dive below the surface, or fly off, in advance of the vessel.
3.30 Behaviour of observed birds was recorded during boat-based surveys, and although this category may be less of a priority for surveyors than count and species identification for example, it was evident that no birds were observed feeding in either 2008/09 or 2009/10. Although it is acknowledged that recording red-throated diver feeding behaviour may be difficult since birds dive beneath the surface to capture prey, or they may be disturbed by the boat’s presence, it is still unlikely that the study area is an important foraging site for the species in comparison to inshore waters.
e) Interpretation of results
3.31 In the South and East North Sea survey sector, Stone et al. (1995) recorded highest densities during December to March, peaking in January (0.93 diver spp. per km2, and abundance of 0.14 red-throated divers per km-1). Birds ranged widely, with highest numbers off the coast of the Netherlands. In the Greater Thames area, densities reached up to 0.49 birds per km2 (lower than more recent surveys). During GWF boat-based surveys, peak densities within the GWF survey area only reached 0.18 birds per km2 in February 2009, suggesting the site has no particular importance for divers during the winter, within the context of the wider southern and eastern North Sea. In comparison, Gill et al. (2004) calculated a peak 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 in winter 2003, which is located within the SPA and closer to the shore.
3.32 The Outer Thames SPA boundary drawn by JNCC represents the optimal solution between protecting a significant proportion of the red-throated diver population across a wide area (given their distribution) and avoiding the inclusion of areas which are apparently of lesser importance to the species. 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/Natural England, 2010). Densities recorded during aerial, boat-based surveys within TH3, GG1-4 and the GWF survey area do not generally reach these levels. Densities of red-throated divers recorded in the TH3 sector were relatively low, with a peak estimate of 0.1 birds per km2 in January-February 2005, although a peak of 0.69 birds per km2 was recorded in February-March 2006, which did exceed the SPA threshold value. In comparison however, densities during the remainder of the winter fell below the threshold value, and ranged from 0.02-0.55 birds per km2.
3.33 Peak count estimates for the smaller GWF study area (turbine areas plus 0-4km buffers) were 112 individuals in February 2009, and 65 individuals in March 2010. These exceed the 1% threshold value of significance with respect to proportions of the SPA population that may be affected by disturbance and displacement effects, assuming that all birds recorded are associated with the SPA, and all birds are affected out to 4km from turbines (as per Maclean et al. 2009).
Planning & Development 18
3.34 It should be remembered that the study area is of greater extent than the GWF turbine boundaries, and so likely effects associated with both turbine areas alone would be smaller. Considering the GWF turbine areas A and B only, monthly numbers peaked at 81 birds (1.3% of the SPA population) in 2008/09, and 23 birds (0.4%) in 2009/10 (Tables 7a and 7b). Of the individual component parts of GWF, density only exceeded the SPA threshold in one month (March 2009) within Area B, reaching 0.78 birds per km2. This figure should, however, be treated with caution due to the relatively small size of site compared to the overall survey area, which may result in skewed density estimations.
3.35 Aerial surveys across Britain recorded 44% of all wintering red-throated divers in the Thames Strategic Area, with highest numbers in block TH2 which is south of the GWF site and within the SPA. One third of the total GB population occurred in this block plus block TH1 south west of GWF, which is also within the SPA, although there was great inter-annual variability in numbers (O’Brien et al. 2008). Population estimates at London Array, which is further inshore than GWF and entirely within the SPA, peaked at 7,844 individuals, due to a large flock of 4,000 individuals aggregating together prior to migration (RPS, 2005).
3.36 Evidence from the boat-based and aerial surveys show that the whole GWF survey area was recorded hosting >1% of the SPA population during the months of February and/or March only, and so may be of some importance if some of those birds overwinter in the SPA. The large population off southeast England is however close to large concentrations off the Belgian and Netherlands coasts, and it is likely that there is regular interchange between these areas, and changes in food availability or weather may result in differences in the British component of the population between years (O’Brien et al. 2008).
Numbers within the GWF itself tended to peak in March 2009, and this corresponds with the northwards spring migration of red-throated diver through the Dover strait, back to breeding areas in northern Europe, and so it is likely that many birds encountered during this peak month will be from other wintering areas off Western Europe (i.e. non-Outer Thames SPA birds).
3.37 It is therefore likely that the GWF study area is relatively unimportant for the species compared to the Outer Thames SPA. Within the GWF survey area, it is apparent that there is an east-west trend in increasing abundance, with relatively few birds being recorded within the eastern parts of the proposed turbine arrays, compared with those recorded in the GGOWF turbine areas further west. This coastal trend is likely, at least in part, to be due to the bathymetry and resultant prey availability in the Thames Strategic Area, although these aspects are indistinguishable between GWF and GGOWF sites, except potentially in the small sandbank areas. In the UK, wintering red-throated diver are associated with shallow (between 0-20m deep and less frequently in depths of around 30m) inshore waters, often occurring within sandy bays, although open coastline is also frequently used (Stone et al., 1995). In contrast, the GWF survey area is located in open sea some 27km from shore, generally in depths of 30-40m, reaching 50m in places (Figure 6).
f) Red-throated diver flight activity and predicted collision risk mortality rates
3.38 Table 8 shows that that during boat-based surveys in 2008-10, between 1.1% and 4.9% of all red-throated divers in flight within the whole GWF study area were recorded within collision risk height bands (>20m). During surveys for the GGOWF, the average proportion was lower, at 0.6%. It should be noted that in the GGOWF ES, although the estimated collision risk was zero
Planning & Development 19
(i.e. no birds flew within the rotor swept area), this was based on calculations for all birds observed at or above 30m. However, only one bird was recorded in flight at 20-30m, and so mortality rates are likely to be negligible.
Table 8: Summary of red-throated diver flight activity during survey periods Species 2004-2006 June 2008- May 2009 June 2009- May 2010
Total Total Total Total Total Total number % at number % at number % at number number number at risk risk at risk risk at risk risk observed observed observed height height height
Red-throated diver 1 150 0.6 15 306 4.9 3 261 1.1
Does not include diver sp. Records
3.39 A summary of flight activity is presented in Table 9.
Table 9: Summary of red-throated diver population and activity 2008-09 and 2009-10 within entire survey area Numbers / Activity detail Year Percentages Total Birds in Flight (all records) 2008-09 306 2009-10 261 Total Snapshots flights within GWF 2008-09 5 2009-10 3 Peak monthly snapshot flights within GWF 2008-09 5 2009-10 2
3.40 Collision Risk Modelling (CRM) calculations were undertaken for the GWF EIA for red-throated diver, in order to estimate additional mortality to the SPA, regional and national populations, caused by individual collisions with turbines. The methodology, based on the Band et al. (2007) model, will be fully presented in the Ornithological Technical Report, and has been summarised in the Galloper Wind Farm - Lesser Black-Backed Gull Collision Risk Modelling Note, submitted to JNCC and Natural England on 29 June, 2011.
3.41 An average proportion of 2% of flights at Potential Collision Height (PCH) was used in the model, based on results from 2004 to 2010. This is reasonably consistent with the mean of 4%, calculated from studies at 15 wind farms by Cook et al. (in prep.). The mean flight height recorded during theses surveys was 4.5m above mean sea level (ABMSL), with a range of 0- 21m, which are both below lower rotor height for the worst-case turbine types considered at GWF. Table 10 below presents the results of the CRM, and shows that even when using a precautionary 95% avoidance rate, an average of only 2.9 collisions will occur each year in turbine areas A and B, which results in an increase in baseline mortality (assuming the Outer Thames SPA adult survival rate is similar to the 0.85 recorded in Garthe and Hüppop, 2004) of 0.3%. When using a 4% flight height at PCH value found by Cook et al. (in prep), mortality rises to 5.5 birds per year, or 0.5% increase in baseline mortality.
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Table 10: Collision risk modelling results for red-throated diver Avoidance rate 2008/09 2009/10 Area A 95% avoidance 2.6 1.4 98% avoidance 1.0 0.6 99.0% avoidance 0.5 0.3 99.5% avoidance 0.3 0.1 99.9% avoidance 0.1 0.03 Area B 95% avoidance 0.34 0.0 98% avoidance 0.14 0.0 99.0% avoidance 0.07 0.0 99.5% avoidance 0.03 0.0 99.9% avoidance 0.01 0.0 Total annual mortality at 99.0% 0.6 0.3
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4 DATA TO INFORM HRA SCREENING FOR LESSER BLACK- BACKED GULL
4.1 The Alde-Ore Estuary SPA is over 27km from the boundary of the GWF. However, as nationally- important numbers of lesser black-backed gulls were recorded within the whole GWF survey area during baseline surveys, it is considered that a formal screening process is required, with respect to assessing the possible impacts of the GWF, alone and in-combination with other wind farms and activities on the SPA population.
4.2 Boat-based surveys will be the primary focus of the assessment for lesser black-backed gull, since aerial surveys were only undertaken during winter months, thereby missing breeding season activity associated with the SPA population.
a) Distribution in the southern North Sea
4.3 The southernmost part of the North Sea is an important corridor for lesser black-backed gulls, 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). From April to August, highest concentrations of birds were recorded by Stone et al. (1995) near colonies along the Dutch coast (2-5 birds per km2), with moderate densities across the southern North Sea (<1.0 bird per km2), reflecting distribution of breeding colonies in Britain and abroad. Until relatively recently the lesser black-backed gull was a complete migrant with only small numbers of birds over-wintering in the UK. Over the latter half of the 20th century, large numbers remained in Britain in winter, mainly in the southwest (Lack 1986). In winter, birds are more commonly found inland than on the coast. From July and August, birds begin the migration to wintering areas in the Bay of Biscay and west Africa, although the distribution is still widespread off continental coasts.
4.4 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 southeast coast of England with in total 7,381 coastal pairs (Mitchell et al. 2004).
b) Aerial surveys
4.5 It is often not possible to identify gulls down to species level during standard aerial seabird survey methodology (e.g. DTI, 2006a; BERR, 2007; DECC, 2009), with lesser black-backed gulls often likely to be classified as ‘black-backed gulls’, ‘large gulls’ or ‘gulls’. Aerial surveys are therefore not likely to be as effective at recording this species as boat-based surveys. Nevertheless, raw counts of aerial surveys in the Thames Strategic Area are presented in Table 11 below.
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Table 11: Potential maximum lesser black-backed gull raw counts per period, Thames aerial surveys 2004/05 to 2007/08 Year Sector Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7
2004/05 TH3 54 (2) 104 (3) 605 (2) 43 (0) n/s n/s 10 (2)
2005/06 TH3 21 (2) 7 (0) 211 (3) 66 (1) n/s n/s n/s
2007/08 TH1 & GG n/s n/s 2,167 (26) 653 (16) n/s n/s n/s Main total includes lesser black-backed gulls, all unidentified gulls, ‘large gulls’ and ‘black-backed gulls’. Number in brackets signifies total of positively identified lesser black-backed gulls. Period 1 = early winter; 2 = Mid winter (1); 3 = Mid winter (2); 4 = Late winter; 5 = Breeding: incubation; 6 = Breeding: chick rearing; 7 = Post fledging/moult
4.6 Since coverage during summer months was very limited, it is difficult to make comparisons with boat-based survey results as to the importance of the wider area for breeding lesser black- backed gulls. Overall, numbers of gulls during winter months were generally likely to be similar to those recorded from boat-based surveys, with a high raw count of 2,167 individuals (including all large gull records) in mid-winter 2007/08 within the Greater Gabbard survey block.
c) Boat-based surveys
4.7 The surveys used to inform the HRA report are the same as those described in the previous section for red-throated diver.
4.8 Large numbers of lesser black-backed gull were recorded in the entire GWF survey area throughout the year, peaking during the late breeding season, in June and July Tables 12a and 12b and Figure 11). Nationally-important numbers of birds were recorded in both survey years, with a peak population estimate of 3,144 birds in June 2008, which would equate to almost all of the current SPA breeding population.
4.9 In winter, numbers hit a winter peak in early January 2009 with an estimated 2,027 individuals in Area B alone, although this number should be treated with some caution, as it is larger than the estimated GWF survey area population, and may be subject to problems of clustered records skewing densities within a small area.
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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 1,000
500
0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month
2008-09 2009-10 current SPA breeding population (1,603 pairs)
Figure 11: Lesser black-backed gull population estimates within the GWF survey area in 2008/09 and 2009/10, showing current SPA breeding population (3,206 individuals). Although the majority of surveys were conducted in regular monthly intervals, some months were missed due to poor weather conditions. In these cases, catch-up surveys were conducted during the first week of the following month. To allow direct comparisons between years, these surveys have been allocated the month of the originally-planned survey dates, e.g. the survey conducted in early November 2008 has been allocated as the October 2008 survey. No survey was conducted which equates to the month of November 2009.
Tables 12a and 12b: Monthly lesser black-backed gull population estimates for GWF survey area and component parts
2008-09 Area Jun Jul Aug Sep Nov (1) Nov (2) Jan (1) Jan (2) Feb Mar Apr May Area A 86 147 62 86 0 36 20 2 116 64 104 110 0-4km buffer 1,124 136 171 75 31 190 96 25 366 220 335 263 Area B 430 494 460 0 70 0 2,027 212 362 212 354 146 0-4km buffer 978 959 637 265 67 22 651 77 409 383 153 352 Total Survey Area 3,144 1,964 1,405 811 192 413 848 243 1,246 1,540 921 1,321
2009-10 Area Jun Jul Aug Sep Oct Nov Dec* Feb (1) Feb (2) Mar Apr May Area A 154 402 85 10 0 n/a 68 0 84 39 218 100 0-4km buffer 270 705 184 149 0 n/a 948 138 56 274 160 115 Area B 847 145 144 16 0 n/a 109 10 494 2 71 545 0-4km buffer 540 324 130 90 1 n/a 375 107 388 680 217 229 Total Survey Area 1,731 2,238 867 568 4 n/a 1,676 312 867 900 789 773 * Area B and 4km buffer are estimated, based on overall survey area density, as survey did not cover this area
4.10 During GGOWF surveys in 2004/05, summer numbers reached an estimated peak of 780 birds in June 2004, and 1,579 birds in May 2005. In winter months, numbers were similar to 2008-10, with peaks of 1,508 birds in March 2005, and of 2,399 birds in December 2005.
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d) Distribution and behaviour
4.11 Although only occasionally recorded to a species level, aerial surveys in the Greater Thames showed that lesser black-backed gulls are likely to be more common in inshore areas than offshore (DTI, 2006a; BERR, 2007). 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, e.g. discards from trawlers working in and passing through the survey area. There was no apparent pattern to the location of these aggregations (Figures 12 and 13).
Figure 12: lesser black-backed gull boat survey counts, 2008/09
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Figure 13: lesser black-backed gull survey counts, 2009/10
4.12 From positively-aged lesser black-backed gulls recorded during boat-based surveys in 2008/09 and 2009/10, it was evident that for most of the year, the majority of birds are adults (an average of around 90%), although the proportions of sub-adults evidently increase from the late breeding season, through to November (peaking at around 50% in October 2009), which coincides with the main protracted autumn exodus of juveniles from late June to November (Cramp and Simmons, 2004).
4.13 There was a slight increase in sub-adult proportions in April and May 2009. This may reflect return immigration into Britain which begins in mid-February and lasts to late May, with a large proportion of immatures among the later arrivals (Cramp and Simmons, 2004) (Figures 14 and 15).
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Lesser black-backed gull age coimposition per month - 2008/09 in GWF survey area
100%
80% Adult 4th Year 60% 3rd Year 2nd Year 40% 1st Year Immature Juvenile Proportion of age class 20%
0% ) ) g p 1 2 ) b r r Jul u e (1) 2 e a p Jun A S v ( v ( ( F M A o o n May N N Jan Ja Annual Month
Figure 14: Age composition of positively-aged lesser black-backed gull recorded during boat-based surveys within the GWF survey area in 2008/09.
4.14 Sample counts of wintering birds in Britain showed that 80–90% were adults, with immatures composed mainly of 2nd- and 3rd-winter birds (Cramp and Simmons, 2004). By the second autumn, birds begin to show a tendency to winter further north, migrating south in August– October, although reappearing in British roosts in rising numbers through December–February. With a growth of British colonies over the last 40 years, adults undertaking long migration are perhaps disadvantaged in competition for territories, hence the tendency to winter closer to breeding grounds.
Lesser black-backed gull age composition per month - 2009/10 in GWF survey area
100%
80% Adult 4th Year 60% 3rd Year 2nd Year 40% 1st Year Immature Juvenile
Proportion of age class 20%
0%
) ) r y Jul (2 a a Jun Aug Sep Oct Dec M Apr M nual Feb (1 Feb An Month
Figure 15: Age composition of positively-aged lesser black-backed gull recorded during boat-based surveys within the WF survey area in 2009/10.
4.15 Lesser black-backed gulls were recorded frequently both in flight and on the sea. Around 10% of all birds were recorded feeding. During boat-based surveys, large flocks of 50-100 birds were commonly recorded, reaching a peak of over 500 birds in June and August 2008. The August flock was recorded in transect and is likely to have played an important part in the total population
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estimates for that month. Survey notes observed that flocks were commonly associated with trawler activity (around 15%, although likely higher due to survey limitations), with scavenging of discards occurring behind the boat. There was also evidence that birds were occasionally attracted to the survey vessel, which may falsely increase population estimates. Observations of birds landing on wind farm infrastructure such as GGOWF turbine bases and meteorological masts, as well as on fishing vessels were also made.
e) Interpretation of results
It can be seen that, in general, lesser black-backed gull activity within the entire GWF survey area is relatively high during the breeding season, with a peak density estimate of 2.8 birds per km2 recorded in June 2008. Numbers in 2009-10 were lower, with a peak density of 2.0 birds per km2 in July 2009. Population estimates within each survey area component regularly exceed the 1% threshold with respect to proportions of the likely current SPA population, assuming that all birds recorded are part of a pair associated with the SPA.
4.16 Population densities recorded during winter months were consistently higher in the GWF compared to the larger South and East North Sea survey area (Stone et al. 1995), in both 2008/09 and 2009/10. It is not clear as to the origins of wintering birds, but it is likely that a combination of non-breeders and those from colonies in more northerly latitudes are found here, with SPA birds migrating south. During migratory periods there is likely to be an exchange of birds between continental Europe and Britain. 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).
f) Lesser black-backed gull flight activity and predicted collision risk mortality rates
4.17 Table 13 shows that that during boat-based surveys in 2008-10, between 14.2% and 20.0% of all lesser black-backed gulls in flight within the whole GWF study area were recorded within collision risk height bands (>20m).
Table 13: Summary of lesser black-backed gull flight activity during survey periods
Species June 2008- May 2009 June 2009- May 2010
Total Total Total Total number % at number % at number number at risk risk at risk risk observed observed height height
lesser black-backed gull 935 6,601 14.2 530 2,651 20.0
4.18 A summary of flight activity is shown below in Table 14.
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Table 14: Summary of lesser black-backed gull population and activity 2008-09 and 2009-10 within entire survey area Numbers / Activity detail Year Percentages Total Birds in Flight (all records) 2008-09 7,116 2009-10 2,658 Total snapshots flights in GWF 2008-09 391 2009-10 220 Peak monthly snapshot flights within WF 2008-09 111 2009-10 60
4.19 An average proportion of 17% of flights at PCH was used in the model, based on results from 2008 to 2010. This is reasonably consistent with the mean of 22% (range 4-46%), calculated from studies at 18 wind farms by Cook et al. (in prep.). The mean flight height recorded during theses surveys was 170m ABMSL (with a range of 0-313m), which is above nominal rotor tip height for the ‘worst-case’ turbines considered in the EIA for GWF. Table 15 below presents the results of the CRM, and shows that when using the recommended lower avoidance rate for lesser black-backed gull of 99.5% (Maclean et al. 2009), 113-165 collisions will occur each year in turbine areas A and B. Evidence from studies at operational wind farms (e.g. Winkelman 1992; Everaert and Kuijken, 2007) however suggests that avoidance rates are likely to be very high, and potentially around 99.9% (23-33 collisions per year), which results in a 7-10% increase in baseline mortality over the current SPA population, using the unlikely assumption that all collisions are by breeding SPA birds. In actuality, the proportion of mortality on SPA birds will be considerably lower.
Table 15: Collision risk modelling results for lesser black-backed gull
Avoidance rate 2008/09 2009/10 Area A 95% avoidance 821 690 98% avoidance 328 276 99.0% avoidance 164 138 99.5% avoidance 82 69 99.9% avoidance 16 14 Area B 95% avoidance 831 435 98% avoidance 332 174 99.0% avoidance 166 87 99.5% avoidance 83 44 99.9% avoidance 17 9
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5 DATA TO INFORM HRA SCREENING FOR GANNET
5.1 The Flamborough Head and Bempton Cliffs SPA is nearly 300km from the boundary of the GWF. However, as gannet have a mean maximum foraging range of 300km+ (Langston, 2010), they are at potential risk of collision from turbines within the GWF site. It was therefore considered by JNCC and Natural England that a formal screening process is required, with respect to assessing the possible impacts of additional mortality due to collisions at the GWF, in-combination with other offshore wind farms along the east coast of England, on the SPA population.
a) Gannet distribution in the North Sea
5.2 Typically, gannets from European colonies migrate southwards towards Iberia and western Africa at the end of the breeding season, particularly with first-years (Wanless, 2002). Large numbers of gannets 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.
5.3 As they get older, gannets tend to winter further north, although experienced adults may still reach as far as northern Africa. Most British and Norwegian birds migrate mainly via the North Sea, and birds from the Channel Islands colonies occur in waters all around Britain (Wanless, 2002). The winter population within the southernmost North Sea area is estimated to be around 10,000 individuals (Stienen et al. 2007).
5.4 Stone et al. (1995) recorded highest densities of gannets in the breeding season surrounding colonies further north in European waters. The southern North Sea area is relatively unimportant for the species, although birds are widely distributed due to its large foraging range. There is a large breeding population of gannets in Britain (around 218,546 AON – Wanless et al. 2005), and the remainder of the northwest European population is over 79,200 pairs (4,200 pairs in Norway, 2,000 in the Faroe Islands, 33,000 in the Republic of Ireland, 24,000 in Iceland, and 16,000 pairs in France; BirdLife International, 2004). Ringing recoveries (Wanless, 2002) suggest that all of these populations may use the southern North Sea at some stage of their life cycle, although most birds on migration down the east coast of England are likely to be from the British and Norwegian populations.
5.5 The closest breeding colonies to the GWF are at Bempton Cliffs (7,859 pairs – Table 16), and in Ortac and Les Etacs in the Channel Islands, where around 7,500 pairs of gannets nest at two long-established gannetries (Veron and Lawlor, 2009). Further afield, Camphuysen (2011a) showed that from ship-based surveys around the Bass Rock colony, with high densities near the colony, and low densities over vast areas 100-450km from the colony. The maximum foraging range was 540km from the colony, with a mean maximum distance of 232km.
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Table 16: Gannet breeding colonies in the East and Southern North Sea Colony Distance Site Survey Date count Count type from GWF Les Etacs 2005 4,862 Occupied nests c.420km Ortac 2005 2,547 Occupied nests c.420km Bempton Cliffs RSPB 2009 7,859 Occupied sites c.275km Troup, Pennan and Lion's Heads SPA 2010 2,787 Occupied nests c.700km Bass Rock 2004 48,065 Occupied nests c.530km
Total 66,120
5.6 Based on what is known about the species’ foraging range, during the breeding season, the GWF may be reachable by individuals from Flamborough Head and Bempton Cliffs SPA, and on occasion from Les Etacs and Ortac, and Bass Rock. For most of the year, it is likely that there is a greater mixture of birds, as gannets, particularly non-breeders, are spread throughout offshore waters, although the shelf edge and outer continental shelf are considered to be relatively important foraging areas (Stone et al. 1995).
b) Gannet foraging around Bempton Cliffs
5.7 In 2010, DECC funded the RSPB to carry out satellite tracking of 14 breeding gannets from Bempton Cliffs during the chick-rearing period, to investigate foraging ranges and destinations in relation to proposal sites for offshore wind farms (Langston, 2011). The tags lasted for 13-84 days, some into October, and showed that, during chick rearing in 2010, the majority of gannet locations were within 50-100km of Bempton Cliffs, overlapping with the proposed Hornsea Round 3 offshore wind farm area in particular (Figure 14). The average foraging range (straight-line distance from Bempton) was 63.6 ± 8.9km, whilst the average length of foraging trip (total distance covered during a foraging trip) was 158.6 ± 22.7 km. There was no evidence that any breeding birds reached the GWF site to forage during the breeding season.
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Figure 14 Satellite tracking locations of gannets from Bempton Cliffs. From Langston (2011).
c) Boat-based surveys
5.8 Gannets were recorded throughout the year within the GWF survey area, peaking at an estimated 1,325 birds in early November 2008. This equates to around 8.4% of the Flamborough Head and Bempton Cliffs SPA populations, assuming all are breeding birds from this colony. Numbers within the GWF site alone peaked at 266 individuals (1.7% of the SPA population) during the same month (Figure 15).
5.9 During summer months numbers were relatively low, normally near the 1% SPA threshold, although there was a peak in April 2010, with an estimated 677 individuals in the whole GWF survey area, which may coincide with peak movements of birds northwards through the English Channel to breeding colonies.
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Gannet Population Estimates per month: GWF Survey Area 2008-10
1,400
1,200
1,000
800
600
No. No. Individuals 400
200
0 l n u t y J c ar a Ju Aug Sep O Nov Dec Jan Feb M Apr M Month
2008-09 2009-10 1% SPA population (157 individuals)
Figure 15: Gannet population estimates within the GWF survey area in 2008/09 and 2009/10, showing 1% of the Flamborough Head and Bempton Cliffs SPA population threshold (157 individuals). Although the majority of surveys were conducted in regular monthly intervals, some months were missed due to poor weather conditions. In these cases, catch-up surveys were conducted during the first week of the following month. To allow direct comparisons between years, these surveys have been allocated the month of the originally-planned survey dates, e.g. the survey conducted in early November 2008 has been allocated as the October 2008 survey. No survey was conducted which equates to the month of November 2009.
5.10 From records of positively-aged gannets recorded during boat-based surveys in 2008/09 and 2009/10, it was evident 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, peaking at 60-70% in August to September (Figures 16 and 17). This likely coincides with the autumn migration southwards, when sub-adults often leave breeding areas some weeks earlier than adults (Cramp and Simmons, 2004).
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Gannet age composition per month - 2008/09 in GWF Survey Area
100% 90% 80% Adult 70% 5th Year 60% 4th Year 3rd Year 50% 2nd Year 40% 1st Year 30% Immature
Proportion of age class 20% Juvenile 10% 0% Jun Jul Aug Sep Nov Nov Jan Jan Feb Mar Apr May (1) (2) (1) (2) Month
Figure 16: Age composition of positively-aged gannets recorded during boat- based surveys within the GWF survey area in 2008/09.
Gannet age composition per month - 2009/10 in GWF Survey Area
100%
80% Adult 5th Year
60% 4th Year 3rd Year 2nd Year 40% 1st Year Immature
Proportion age of class 20% Juvenile
0% Jun Jul Aug Sep Oct Dec Feb Feb Mar Apr May (1) (2) Month
Figure 17: Age composition of positively-aged gannets recorded during boat- based surveys within the GWF survey area in 2008/09.
5.11 Throughout the winter the sub-adult proportion is low. Veron and Lawlor (2009) observed that after their second winter, immature birds from Channel Island colonies tend to summer in northern waters, often around different gannetries. By the time of the fifth year, gannets 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.
Immatures are widely dispersed in the North Sea between spring and autumn, increased later by post-fledging dispersal of juveniles (Cramp and Simmons, 2004), and this may explain the slightly higher proportions during later summer months.
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d) Gannet flight activity and predicted collision risk mortality rates
5.12 Table 17 shows that that during boat-based surveys in 2008-10, between 6% and 11% of all gannets in flight within the whole GWF survey area were recorded within collision risk height bands (>20m).
Table 17: Summary of gannet flight activity during survey periods Species 2004-2006 June 2008- May 2009 June 2009- May 2010
Total Total Total Total Total Total number % at number % at number % at number number number at risk risk at risk risk at risk risk observed observed observed height height height
Gannet 63 987 6% 165 1,961 8% 208 1,899 11%
Table 18: Summary of gannet population and activity 2008-09 and 2009-10 within entire survey area Numbers / Activity detail Year Percentages Total Birds in Flight (all records) 2008-09 1,961 2009-10 1,899 Total snapshots flights in GWF 2008-09 109 2009-10 101 Peak monthly snapshot flights within WF 2008-09 27 2009-10 42
5.13 An average proportion of 8% of flights at PCH was used in the model, based on results from 2004 to 2010. This is reasonably consistent with the mean of 14% (range 5-36%), calculated from studies at 22 wind farms by Cook et al. (in prep.). The mean flight height recorded during these surveys was 10m ABMSL (with a range of 0-200m), which would be below lower rotor tip height for the ‘worst-case’ turbines considered in the EIA for GWF. Tables 18 and 19 presents the results of the CRM, and shows that when using the recommended lower avoidance rate for gannet of 99.5% (Maclean et al. 2009), 23-28 collisions will occur each year in turbine areas A and B. This would result in an increase in baseline mortality of 1.8-2.2% (using an adult survival rate of 0.92, as per Wanless et al. 2006) over the current Flamborough Head and Bempton Cliffs SPA population, based on the unlikely assumption that all collisions are by breeding SPA birds. In actuality, mortality rates on SPA birds are be considerably lower, with gannets likely ranging widely throughout the year, and being associated with a variety of colonies in Northwest Europe. In addition, large numbers of birds present are likely to be wandering sub-adults or non-breeders that are not part of any breeding population.
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Table 19: Collision risk modelling results for gannet
Avoidance rate 2008/09 2009/10 Area A 95% avoidance 183.4 77.9 98% avoidance 73.4 31.2 99.0% avoidance 36.7 15.6 99.5% avoidance 18.3 7.8 99.9% avoidance 3.7 1.6 Area B 95% avoidance 96.0 150.1 98% avoidance 38.4 60.0 99.0% avoidance 19.2 30.0 99.5% avoidance 9.6 15.0 99.9% avoidance 1.9 150.1 Total annual mortality at 99.5% 27.9 22.8
5.14 The 99.5% avoidance rate used is considered to be a realistic, even conservative estimate of true avoidance rates for this species. Extensive post-construction monitoring results at Horns Rev and Nysted offshore wind farms in Denmark showed that gannets were seldom seen flying between turbines (‘macro avoidance’) (Petersen et al. 2006), whereas other species such as gulls showed little avoidance behaviour until close by (‘micro avoidance’).
5.15 At the Egmond aan Zee (OWEZ) Wind Farm in The Netherlands, distribution patterns suggested that gannets again avoided the entire wind farm (Krijgsveld et al. 2010) (Figures 18 and 19).
Figure 18: Flight paths of gannets (left) and gulls (right) flying in the wind farm area. Data observed visually from the met mast (star in centre graph). Squares depict the turbines, rings are placed at intervals of 1 NM=1.85 km; max distance from metmast to furthermost turbine is c. 5 km. From Krijgsveld et al. (2010).
5.16 Gannets changed their flight direction relatively close to the wind farm (down to 500m) compared to other sensitive species such as divers which generally avoided the wind farm at greater distances (>2-4km). They only very occasionally ventured briefly into the wind farm during foraging flights. Of the birds that did enter the wind farm, all species showed very strong avoidance of individual turbines (micro-avoidance). These surveys suggest that the overall avoidance rate for gannet (macro and micro avoidance combined) is likely to be very high.
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Figure 19. Relative distribution of several species within and outside the OWEZ wind farm, The Netherlands. Given the layout of the wind farm within the observed area, the proportion of birds inside the wind farm should be approximately equal when no avoidance occurs. Note that all species presented occurred in higher percentages outside the wind farm. From Krijgsveld et al. (2010).
5.17 Cumulative gannet collision mortality calculations were extended to cover a wider area along the east coast of Britain, due to the species’ extensive foraging range. All offshore wind farms were therefore considered, from the Beatrice Demonstrator to the north, to those in the Thames Strategic Area in southeast England (Table 20). In some cases, CRM calculations were not conducted for gannet, and so only a qualitative assessment was possible.
Table 20: Estimated annual collision rates (99.5% avoidance rate) of gannet at constructed, consented and proposed OFWs for which ES data was obtained
Wind Farm Number of Status Predicted Annual turbines Gannet Mortality
Galloper >140 Construction planned for 23-28 2014-2016
Greater Gabbard 140 First foundation was n/a installed in March 2011. Completion by 2012
London Array I and II 175 + 166 First foundation was n/a installed in March 2011. Completion by 2012. Phase II after 2012.
Gunfleet Sands I, II 48 (+2 for Operational since March n/a and III phase III) 2010
Kentish Flats and 30 + 51 Phase 1 operational since n/a extension June 2005. Extension planned 2013-2014
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Wind Farm Number of Status Predicted Annual turbines Gannet Mortality
Thanet 100 Operational since May 0.5 [5] 2010
Westermost Rough 80 Submitted – construction 0.1 [1.3] to begin in 2014
Scroby Sands 30 Operational since n/a December 2004
Humber Gateway 83 Consent was granted in 0.8 [8] February 2011 and the work is estimated to take about 2 years.
Lincs 75 Construction began in 2.1 [21] March 2011, due to be completed in 2012
Lynn and Inner 54 Operational since March 0.02 [0.2] Dowsing 2009
Sheringham Shoal 88 Under construction – to 7.8 [47*] be completed in 2011
Teeside 27 Approved - to be 3 [30] completed in 2012
Race Bank 88 An application for consent 49.5 [297*] was submitted in 2009.
Triton Knoll 333 Early planning – 68 [685] construction expected to start in 2017
Dudgeon 168 Operational by 2014-15 99 [994]
Docking Shoal 83-177 Consent application 18.3 [113*] submitted – operational by 2015
Beatrice 2 Operational since 2008 1 [10] Demonstrator
Total 273-278 Numbers in brackets refer to the original figures at 95% avoidance rate presented in ESs. * = 97% avoidance rate
5.18 The total cumulative annual mortality predicted from sites where CRM figures were available rose from 23-28 birds at GWF alone, to 273-278 for the entire east coast. It is worth emphasising that
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the collision risk estimates are based on year round activity so impacts on breeding birds are inflated by the additional activity modelled for wintering birds, more likely to come from other colonies. It was not however practicable to partition the collision risk by season for any of the sites, based on the data presented.
5.19 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.
5.20 In the draft ES for the Kentish Flats Extension phase, a mean count of <0.07 gannets were recorded within the wind farm risk area during surveys in 2005-07, and 2009-10. This inshore site is unlikely to contribute significantly to additive mortality rates (<1 bird per annum).
5.21 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.
5.22 No CRM data were available for Gunfleet Sands, although the first year post construction monitoring report recorded no gannets flying at PCH within the risk zone, and only 8 individuals within the boat survey area between October 2007 and March 2008 (RPS, 2008). Mortality rates are therefore likely to be very low.
5.23 No data were available for Scroby Sands, although due to its small size and proximity to the coast, gannet activity levels are likely to be very low. It has been operational since 2004 and so its effects were likely incorporated into the baseline survey results for GWF from 2008-10.
5.24 In summary, if the true annual collision mortality at all east coast wind farm projects was at least 280 birds (not including other sites where quantitative information was not available), this would increase mortality above the background rate to 22.0-22.5% on the Flamborough Head and Bempton Cliffs SPA breeding population, although only a 2.6% increase on the east coast Britain population, and a 0.8% increase on the national breeding population.
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6 ASSESSMENT OF LIKELY SIGNIFICANT EFFECTS
6.1 The nature of the potential effects of the GWF development, both alone and in-combination, are outlined in this section, in relation to construction and operation phases. Assessment of impacts specifically arising from the process of decommissioning have been scoped out since they are of a similar nature to construction issues, but often of a smaller scale and shorter duration. Based on reviews of the effects of offshore wind farms on birds, e.g. Drewitt and Langston (2006), Dierschke et al. (2006) and Langston (2010), the GWF has the potential to adversely affect SPAs as a result of:
• Habitat (bird and prey species) loss and fragmentation;
• Disturbance (noise, acoustic and visual);
• Displacement (effective habitat loss);
• Collision risk with turbines; and
• Barrier effects caused by the wind farm or individual turbines.
6.2 Each of these issues is considered in turn below for red-throated diver and lesser black-backed gull. Only collision risk is considered to be relevant to the gannet population within the GWF.
6.3 It is possible that in-combination effects may occur with other wind farms in the Thames Strategic Area, as well as non-wind farm activities in the area.
6.4 It is considered that the following plans and projects have the potential for in-combination effects with the GWF Project on red-throated diver and lesser black-backed gull:
• GGOWF;
• London Array (both phases);
• Gunfleet Sands I, II and III;
• East Anglia Offshore Wind Farm project ONE (East Anglia ONE)*;
• Kentish Flats (including extension);
• Thanet; and
• Scroby Sands*;
*not in the Thames Strategic Area
6.5 In response to comments on the draft report by JNCC and Natural England, the cumulative assessment of lesser black-backed gull considers plans and projects within the foraging range of the species, and is therefore not limited to the Thames Strategic Area. The first four projects listed above are within the core 40km foraging range of lesser black-backed gulls (e.g. Ratcliffe et al. 2000; Camphuysen, 2008) from the Alde-Ore Estuary SPA, and are therefore included. As a
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precautionary measure, the final three sites within the upper regular foraging range of 80km (e.g. Camphuysen, 2008; Shamoun-Baranes et al. 2010), and have also been considered, although are less likely to be used by SPA birds.
6.6 As surveys are on-going for the East Anglia ONE project, little relevant data have been made available to date which can be used in a cumulative assessment. Preliminary lesser black- backed gull collision mortality calculations were however obtained from the developer, which can be included in this assessment.
6.7 The following offshore wind farm projects have also been considered in the cumulative collision risk assessment for gannet: Teeside, Westermost Rough, Humber Gateway, Lynn and Inner Dowsing, Lincs, Docking Shoal, Race Bank, Triton Knoll, Sheringham Shoal and Dudgeon.
6.8 Based on assessments in DTI (2006b) and JNCC/Natural England (2010), the main non-wind farm threats to red-throated diver and lesser black-backed gull are considered to be:
• Loss of habitat due to dredging, dumping and aggregate extraction; and
• Fishing and shipping, through disturbance-displacement to individuals and prey.
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a) Potential Impacts on Red-throated Diver
i. Construction
Habitat Loss Potential Impacts Pathway: Loss of habitat for foraging or loafing birds associated with the SPA due to turbine construction. Sub-sea transmission cable installation may result in loss of SPA habitats associated with red-throated diver prey species Relevant Conservation Population Size Objectives Components Habitat Extent Prey Species Potential effects on SPA Widely-ranging birds from the SPA may lose areas of sea for foraging and, therefore, individuals’ fitness may be affected, ultimately resulting in qualifying species increased mortality or reduction in fecundity. Loss of seabed habitat for prey species along the export cable route would result in the loss of a food resource to red-throated diver in the SPA, reducing fitness and potentially increasing mortality of birds. Risk of Likely Significant Aerial surveys show that red-throated divers are wide-ranging within the Thames Strategic area, and the proportion of sea directly lost to turbine Effect (LSE) construction outside of the SPA and, therefore, main foraging areas, is negligible. No SPA sublittoral, shallow (<20m) sandbank habitat will be lost, which is the priority habitat for red-throated diver referred to in the Conservation Objectives. The loss in extent of suitable SPA habitat for divers from transmission cable installation will be both temporary, and negligible in magnitude. Any effects on SPA seabed habitat are likely to be less extensive than the dredging activity that currently takes place in the Thames area. DTI (2006b) report that there is considerable evidence in the southern North Sea to demonstrate that the highly dynamic, sediment-rich waters, together with largely opportunistic benthic species, lead to rapid re-establishment of the fauna, e.g. within months or by the following year, in response to seabed disturbance from dredging, dumping and aggregates extraction (e.g. Newell et al, 2004 and MMS, 1999). The red-throated diver population will therefore be unaffected by any temporary habitat loss.
Conclusion: No Likely Significant Effect Potential in-combination The available ESs for other offshore wind farms in the Thames Strategic Area (GGOWF, London Array, Gunfleet Sands, Kentish Flats and Thanet) all effects predict non-significant impacts on red-throated diver. Only small areas of habitat would be lost, amounting to a total of less than 0.5% of the SPA (DTI, 2006b). GWF alone, or in-combination with other wind farms, will therefore not contribute to any significant habitat loss as it lies outside of the SPA boundary. The transmission cable will be installed undersea and so any habitat loss would only be restricted to the short-term, during installation and re- colonisation of benthic fauna. As reported above, fauna are likely to re-establish themselves rapidly in response to other activities within the SPA such as dredging.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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Disturbance Potential Impacts Disturbance caused by construction operations such as vessel movements or piling activities may directly displace birds from foraging or loafing areas. Pathway: Secondary impacts include disturbance to the seabed and water column by construction activities, or disturbance to prey species. Relevant Conservation Population Size Objectives Components Prey Species Potential effects on SPA Although temporary in nature, it is possible that individual survival rates may be affected at least for one winter or following breeding season during qualifying species construction.
Disturbance to the seabed may disturb prey species and thereby potentially remove or reduce a food resource over the period of construction Risk of Likely Significant Garthe and Hüppop (2004) rated red-throated diver as being a species of the highest sensitivity to boat-based disturbance, and the general sensitivity Effect (LSE) of the species to disturbance was considered by Maclean et al. (2009) to be Very High.
Evidence from boat-based surveys at GWF suggests that red-throated divers near vessels would be displaced. This source of disturbance is however likely to occur currently due to the high volumes of boat traffic already present in the Thames Strategic Area. Despite this, the area is nationally important for the species, and numbers have remained stable, at least in recent years. It is, therefore, likely that any displacement effect would be temporary and that birds would return if the area was of sufficient quality for food resources.
Disturbance effects would likely be an issue only during construction and maintenance in winter months. 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 (peak of 11 birds).
As construction activities generally are concentrated on one or two turbines per day (as per GGOWF construction), it is likely to be localised in nature and occur over the short-term only, therefore removing any additive effects over the lifespan of the wind farm. Construction activity is likely to be less intensive during the winter due to adverse weather conditions, and therefore will reduce the likelihood of impacts in the period of highest diver activity.
In general, the effect of service boats is likely to be of a lesser magnitude than assuming total displacement of all birds from the wind farm area and 4km buffer. Although disturbance to peak numbers of 112 birds (1.7% of SPA population) within the GWF study area (including 4k buffer) is potentially significant in the context of the SPA population (albeit in the short-term only), the overall effect of displacement by the service boats on site integrity would be moderated as the population level effect is expected to be proportionally much smaller than the displaced area, occurring within up to 4km of the construction activity only. As numbers peak during the migratory period in March, it is unlikely that all birds are associated with the SPA, and therefore it is likely that less than 1% of the SPA population would be affected at any time.
Construction activity associated with the transmission route within the SPA would only potentially affect divers during winter months when birds are present. Nevertheless, it is considered unlikely that there will be a significant disturbance effect even if localised cable-laying activities were to take
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Disturbance place during this period. Any effects would be temporary and unlikely to affect individuals’ fitness to a significant extent over a whole winter, as birds are likely to naturally forage widely in response to prey movements. No potential LSE was highlighted in the GGOWF AA (DTI, 2006b) as a result of cable-laying activities, which were similar in nature and location to the proposed GWF route.
Conclusion: No Likely Significant Effect Potential in-combination By the time that GWF will reach its construction phase, the GGOWF will be fully operational and so disturbance caused by maintenance activities in effects the latter site will be less frequent and of low magnitude (assuming that birds continue to use the wind farm area and surrounding sea post construction). As such, the in-combination disturbance effects of GWF and GGOWF are unlikely to be significant within the context of the SPA population.
As construction effects are likely to be restricted to the short-term period of construction, any cumulative impacts will only occur if the construction phases of wind farm projects are coincidental. It is evident that most OWFs in the Thames Strategic Area will be operational by the time that GWF is in-construction. The only possibility of overlapping construction activity is with the planned London Array Phase II and East Anglia ONE projects. No data are available for these and so a cumulative disturbance assessment is not possible, although it is considered unlikely that any significant effects will result, due to the distance between sites and the localised effects of construction activities. The East Anglia ONE site is further offshore and unlikely to be used in any great numbers by the species. Red-throated divers are likely to be habituated to some extent to boat traffic in the Thames Strategic Area already.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
ii. Operation
Displacement Potential Impacts Long-term displacement of foraging or loafing birds in the vicinity of physical infrastructure associated with the wind farm Pathway: Secondary effects of displacement due to operational processes include alteration of the wave action surrounding the turbines which may change prey distribution. Relevant Conservation Population Size Objectives Components Prey Species Potential effects on SPA Effective loss of habitat equating to at most the entire turbine area plus a buffer zone of up to 4km (as per Maclean et al. 2009). qualifying species Vulnerability to displacement can be assessed against Garthe and Hüppop’s (2004) habitat flexibility scoring system, which rates red-throated diver as being among the most sensitive of species assessed, being reliant on specific habitat characteristics.
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Displacement Risk of Likely Significant Evidence from European studies of offshore wind farms at Horns Rev in Denmark (Christensen et al. 2004; Christensen and Hounisen, 2004) and Effect (LSE) Danish (Nysted) and German sites (Dierschke and Garthe 2006) suggests that divers do generally avoid wind farms, although may still be found near and within turbine areas if the habitat is of sufficient quality. At Horns Rev Offshore Wind Farm in Denmark, no divers were recorded in flight entering the wind farm area, although one diver was recorded foraging within the wind farm, and several were observed foraging at distances of 100-800m from the nearest turbine (Christensen et al. 2004). Although this area is a migration route rather than an overwintering site, the presence of divers within 800m does, however, show that birds may be able to forage relatively close to outermost turbines, even with little chance of habituation.
The Dutch Egmond aan Zee offshore wind farm (OWEZ) is situated in waters that are somewhat similar to Horns Rev, and divers often winter in the area in good numbers (Leopold et al. 2004). Some divers were seen within the perimeter of OWEZ during the first year post-construction surveys, but mostly near the edges of the wind farm (Leopold et al. 2010). Modelling results showed significant differences in numbers due to distance to coast, but effects related to the presence of the wind farms on the distribution pattern of local birds were mostly insignificant. This shows that any avoidance is less than 100% (contrary to the preliminary results of the studies at Horns Rev).
During monitoring studies of red-throated diver at the Kentish Flats Offshore Wind Farm in the Outer Thames in 2008-09, an observable shift away from the wind turbines was largely found within 500m (Percival 2009). It was suggested that the magnitude of this displacement may be decreasing through time, potentially due to habituation, although this was not statistically tested. No significant differences in numbers were recorded during post- construction monitoring at Burbo Bank offshore wind farm (CMACS, 2008).
Within two Appropriate Assessments for London Array and Gunfleet Sands 2, the buffer zone for red-throated diver was considered to be 1km. This was assumed to be sufficient to capture the significant proportion of the population of red-throated divers that would be displaced from the wind farm and the surrounding area (London Array Ltd Scoping Response to Galloper Wind Farm, July 2011).
Although it is likely that red-throated diver would be relatively sensitive to the presence of the wind farm as a whole, the displacement of up to 112 birds, or 1.7% of the SPA population from the GWF study area (out to 4km) is likely to be an overestimate of the likely magnitude of impacts as (i) displacement is likely to be less than 4km and therefore many birds would be able to make use of the GWF buffer zone outside of the SPA; and (ii) the GWF population is likely to consist of many overwintering non-SPA birds from outside of the region passing through on migration to breeding areas in northern Europe. Aerial survey results and data collected for the southern North Sea, suggest the GWF site is sub-optimal for the species, likely due to the distance from the coast and water depth found within. Distribution maps of the GWF survey area and Thames Strategic Area show that birds are found in higher concentrations further inshore, with highest densities likely found within the Outer Thames SPA. 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 associated with the SPA, thereby reducing the likelihood of significant effects on its population to below 1%.
Although birds may regularly redistribute across the Thames Strategic Area in response to food sources, during aerial surveys sector TH3 always held lowest diver densities in winter 2004/05 and only in Period 4 (February-March) in 2005/06 were numbers relatively high, when birds were on migration. Numbers were however very low in the similar period for Greater Gabbard aerial surveys in 2007/08, compared to in TH1. It is therefore likely that any
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Displacement displacement of low numbers of red-throated divers could be absorbed by a number of adjacent areas of apparently better habitat used regularly by red-throated divers, including those TH sectors further inshore, and also around The Wash area, just further north, which would dilute any displacement effects on the Outer Thames SPA to insignificant levels.
In general, any increases in mortality to the SPA or regional populations as a result of displacement will be insignificant (<1%), as (i) it would only be expected to affect any individuals during the short-term (during part of the spring migratory period); (ii) displacement would occur at distances of less than 4km and so birds would be displaced into the GWF buffer rather than the SPA; and (iii) the GWF population is likely made up of a large proportion of non-SPA birds on migration north.
Conclusion: No Likely Significant Effect Potential in-combination The proportion of the Outer Thames SPA population recorded within OWFs in the Thames Strategic Area was very high – indeed it cumulatively effects exceeded the citation figure. This high figure was mainly due to results of the February 2004 survey at London Array which recorded a single flock of 4,000 birds being seen flying through the area, with 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 have been present across the Thames Strategic area during winter months. This would likely lead to a large overestimation in numbers and actual risks involved (the site was used only briefly by such large numbers). Excluding this, numbers only reached 8.4% of the SPA population.
Cumulatively, GWF and GGOWF accounted for 3.1% of the SPA total, but as both are outwith the SPA boundaries, the proportion of SPA birds potentially displaced cannot accurately be calculated. The inter-annual variation of diver distribution within the Thames Strategic Area indicates that divers range widely and therefore utilise different areas. It is, therefore, unlikely that displaced divers will be lost to the population as the would be able to locate alternative suitable habitat elsewhere in the Thames or The Wash areas.
Due to the long-term dredging activity in the area and the wide-ranging nature of red-throated diver, it is likely that the current population is already adapted to such operations, and that effects would be short-term and temporary. It is expected that any increase in displacement effects would only be potentially significant when there was a concentration of activity in a single year within the main foraging areas for the species. It is, therefore, concluded that combining the offshore wind farms with the ongoing effects of dumping and extraction will not create in-combination effects that are significant.
Implementation of safety zones around wind turbines may reduce the fishing activity from taking place within the site. This may have a positive benefit for red-throated diver by reducing disturbance effects, although it is unclear whether increased fishing would occur within the SPA.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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Collision Risk Potential Impacts Collision of a bird with the turbine rotors is almost certain to result in the death of the bird and a loss to the population. Pathway: Relevant Conservation Population Size Objectives Components Potential effects on SPA The effect of an individual loss on a population is influenced by several characteristics of the affected population, notably its size, density, recruitment qualifying species 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, which includes divers.
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. Risk of Likely Significant Garthe and Hüppop (2004) list the red-throated diver’s annual survival rate to be 0.84, which would be classed as of medium sensitivity by Maclean et Effect (LSE) al. (2009). Although the species is relatively un-manoeuvrable in flight, it is evident that divers usually avoid offshore wind farms altogether (e.g. Christensen et al. 2004), thus resulting in still high predicted lower avoidance rates of 99.0% (Maclean et al. 2009).
An average of 2% of birds were recorded flying PCH (<20m) during baseline surveys in 2004-10. Collision risk modelling resulted in predicted annual mortality of 0.3-0.6 birds (99.0% avoidance), or 0.6-1.0 birds at 98% avoidance. Even when considering twice as many birds at PCH (as per Cook et al. in prep), additional mortality is still less than 1%. To reach a 1% rise in mortality rate, at least 9 birds would have to collide with turbines each year, assuming all are from the SPA. This is considered unlikely. As birds are found in large numbers outside of the SPA boundary, recruitment to the SPA population in response to any losses is likely.
The possibility of divers flushed by boats flying into the rotor swept area was raised by DTI (2006b) in the GGOWF AA, but it was noted at the London Array that the very large majority of individuals flew off below rotor height, by a low, direct flight, and Norman and Ellis (2005) concluded that disturbed birds are at a low risk of collision. This also appeared to be the case during GWF surveys.
All other wind farm studies undertaken to date indicate that the majority of divers fly below 20m above sea surface (e.g. Cook et al. in prep.). At London Array one out of over 500 divers studied was observed flying above 20m (Norman and Ellis, 2005) and between 95.5 and 97.5% of divers flew below 15m. Studies undertaken at Thanet indicated that a total of 45 red-throated divers per year might fly through the wind farm at rotor height (Royal Haskoning, 2005 and 2006). Other studies have indicated similarly low occurrences of divers flying at rotor height, including .
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Collision Risk Conclusion: No Likely Significant Effect Potential in-combination A review of collision risk estimates for all wind farms within the Thames Strategic Area (where data were available – GGOWF, Kentish Flats and effects Thanet) resulted in a cumulative mortality of 5.8-6.1 birds per year (<1% increase in SPA baseline mortality), which includes the GWF total, using a 99.0% avoidance rate. During London Array baseline studies, the mean count of flying red-throated divers at PCH within the wind farm and the 1km buffer was between 1.2 and 5.5 individuals, depending on whether the large flock of 4,000 individuals was considered. It was predicted that a significant effect on the regional population would result when a low avoidance rate of around 96% was used for the low value, and around 99.3% for the higher value. Additional mortality is therefore likely to be low, and remain <1%.
The low levels of predicted mortality due to collisions at other sites, reported above reflect the fact that the vast majority of flights in the Thames Strategic Area were recorded below collision height. Although collision risk data from other sites in the Thames area are often not directly comparable, such in-combination losses are not expected to reach significance in terms of the SPA population (<1%).
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
Barrier Effects Potential Impacts 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. Pathway: Relevant Conservation Population Size Objectives Components Potential effects on SPA 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, qualifying species this may result in greater energy expenditure. By implication, this will reduce the efficiency with which they accumulate reserves, potentially affecting their survival or later breeding success. During the lifetime of the offshore wind farm, there is evidence that some birds may habituate to the presence of turbines (e.g. Winkelman, 1992; Percival 2009), and so this effect is likely to be greatest in the short-term. Risk of Likely Significant 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 Effect (LSE) will act as a barrier. This is based on biological characteristics (e.g. wing loading) as well as the sensitivity of species to turbines. Red-throated diver was rated as being of “high” sensitivity to barrier effects by Maclean et al. (2009).
Overall, 71-86% at Horns Rev, and 78% at Nysted, of all bird flocks, including divers, scoters and eider, heading for the wind farm at 1.5-2.0km distance avoided entering into the wind farm between the turbine rows (Petersen et al. 2006). There was considerable movement of birds along the periphery of both wind farms, as birds preferentially flew around rather than between the turbines. 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. Such
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Barrier Effects avoidance was calculated to add an additional period of flight equivalent to an extra 0.5-0.7% on normal migration costs of eiders migrating through Nysted.
Although red-throated diver are likely to range widely within the Thames Strategic Area throughout the winter, there is no evidence from any of the surveys undertaken that there are clear patterns of movement. It is acknowledged that information on preferred foraging areas is incomplete, but there is no evidence to suggest that birds must commute in the vicinity of the GWF or GGOWF to reach important feeding areas. No such behaviour has been recorded at any of the other offshore wind farm locations in the Thames area, according to DTI (2006b). Winkelman (1992) reported on large-scale autumn migrations at a wind farm in Oosterbierum in the Netherlands, and noted that larger species (likely to include divers) reacted at the greatest distances compared to smaller passerines during daylight hours. .
A peak monthly snapshot count of five birds was recorded within the two GWF turbine areas, which equates to less than 1% of the SPA population. Using this figure (as per Maclean et al. 2009), it is evident that no significant barrier effects are likely.
Conclusion: No Likely Significant Effect Potential in-combination Birds may pass through the wind farm areas during the migration period and, therefore, the site may pose a barrier to migratory movements. Data effects from aerial surveys prior to, during and post construction of the Horns Rev offshore wind farm showed that divers showed almost complete avoidance of the wind farm area in the first three years post construction (Petersen et al. 2006). Although numbers were relatively low, concerns were expressed about the potential for cumulative impacts of multiple offshore wind farms along the flyway for divers.
Drewitt and Langston (2006) summarised data on barrier effects of offshore developments, and concluded that none of the barrier effects identified had significant impacts on populations. They identified example scenarios where a population level impact might be seen, including where several wind farms interact cumulatively to create an extensive barrier which could lead to diversions. These scenarios would not appear to be present in this case, and even if such an effect was present for migratory birds, it is unlikely that the majority would be from the SPA. Resting and foraging areas are both marine so resting/foraging journeys are unlikely to be comparable to a land-roosting bird.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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b) Potential Impacts on lesser black-backed gull
i. Construction
Habitat Loss Potential Impacts Loss of habitat for foraging or loafing birds associated with the SPA due to turbine construction. Pathway: Relevant Conservation Disturbance Objectives Components Extent of Distribution of Habitat Food Availability Potential effects on SPA Widely-ranging birds from SPA may lose areas of sea for foraging and therefore individuals’ fitness may be affected, ultimately resulting in qualifying species increased mortality. Risk of Likely Significant The GWF area is not within the SPA boundary. Lesser black-backed gull are wide-ranging within the Thames Strategic Area, and the amount Effect (LSE) of sea directly lost to turbine construction outside of the SPA and, therefore, main foraging areas, is negligible. Lesser black-backed gull is rated as being of “Very Low” sensitivity to habitat loss by Maclean et al. (2009).
Conclusion: No Likely Significant Effect Potential in-combination GWF alone, or in-combination with other offshore wind farms, will not contribute to any habitat loss as they lie outside of the SPA boundary. effects The opportunistic, wide-ranging nature of the species means that cumulative habitat loss for SPA-associated birds will be negligible within the context of upper regular foraging range of up to at least 80km (Camphuysen et al. 2008; Shamoun-Baranes et al. 2011).
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
Disturbance Potential Impacts Disturbance caused by construction operations such as vessel movements or piling activities may directly displace birds from foraging or Pathway: loafing areas.
Secondary impacts include disturbance to the seabed and water column by construction activities. Relevant Conservation Disturbance Objectives Components Food Availability Potential effects on SPA Although temporary in nature, it is possible that survival rates may be affected at least for one winter/breeding season during construction. qualifying species Disturbance to the seabed may disturb prey species and thereby potentially remove or reduce a food resource over the period of construction
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Disturbance Risk of Likely Significant It was evident from surveys that most gull species, including lesser black-backed gull, remain undisturbed by the presence of boats even Effect (LSE) when in close proximity. This is likely reflected in the species’ foraging strategy of taking discards close to fishing vessels. As such, 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 by Maclean et al. (2009) to be Low.
Within the GWF site, numbers during the breeding season peaked at 1,001 birds in June 2009, representing 2.3% of the cited Alde-Ore Estuary SPA population. It is considered that this level of disturbance is unlikely to occur as it was evident from GWF surveys that lesser black-backed gull are not affected by the presence of human-related activities, often being actively attracted to fishing vessels in search of food. Gulls are also even expected to tolerate pile-driving activities, as birds have rapidly colonised industrial sites across the UK despite high intensity machinery operations, for example at landfill sites and quarries. Visual observations by Leopold and Camphuysen (2007) before and during three pile driving sessions at OWEZ in the Netherlands did not detect any noticeable reactions of gulls to construction activities.
The GGOWF annual report for 2009/10 (construction year) reported a decline in lesser black-backed gull numbers compared to the previous year (pre-construction). A more in-depth assessment of monthly population estimates however show that numbers were lower in June and August surveys in 2009, compared to the previous year (Figure 11). This cannot be due to disturbance effects as construction only commenced after the August 2009 survey. Similarly, in some winter months in 2009/10, no construction activity took place on the same day as boat-based surveys, yet populations were regularly lower in the second year. A General Linear Mixed Model for the GWF Ornithological Technical Report showed no evidence to support the theory that there were any reductions in numbers due to construction activities.
It can therefore be concluded that any temporary displacement of birds will have no observable impact on any individual’s fitness or breeding success, due to the species’ tolerance of human activities, and birds’ flexible foraging strategies.
Although lesser black-backed gull may forage for fish within the offshore wind farm, which may be displaced by construction-related disturbance events, there is no evidence to indicate that these prey items will not return to the area once construction is complete, and so any effects will be short-term and temporary in nature.
Conclusion: No Likely Significant Effect Potential in-combination By the time that GWF will reach its construction phase, other wind farms (with the possible exception of the London Array Phase II and East effects Anglia ONE) will be fully operational and so disturbance is unlikely to be significant within the context of the SPA population. Cumulative disturbance due to maintenance activities is considered very unlikely due to the species’ tolerance for human activity.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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ii. Operation
Displacement Potential Impacts Long-term displacement of foraging or loafing birds in the vicinity of physical infrastructure associated with the wind farm Pathway: Secondary effects of displacement due to operational processes include alteration of the wave action surrounding the turbines which may change prey distribution. Relevant Conservation Disturbance Objectives Components Food Availability Potential effects on SPA Effective loss of habitat equating to, at most, the entire turbine area plus a buffer zone of up to 4km (as per Maclean et al. 2009). qualifying species Risk of Likely Significant Maclean et al. (2009) rates lesser black-backed gull as being of ‘Negligible’ sensitivity to habitat limitations, due to the wide ranging nature of Effect (LSE) the species.
Lesser black-backed gulls were often seen within the perimeters of the operational Dutch offshore wind farms by Leopold et al. (2010), sometimes resting on the water or on the monopole structures, or feeding in the tidal wakes of the monopiles. The largest impact of the wind farms was considered to be the exclusion of fishing vessels within their boundaries. Large, fishing-vessel related concentrations of gulls therefore by definition occur only outside the wind farms and this could result in apparent avoidance of the turbines. This, however was not found in the modelling results.
Post-construction monitoring of the OWEZ wind farm by Krijgsveld et al. (2010) showed that gulls showed no avoidance of the entire wind farm (macro avoidance), and were commonly recorded foraging within. Of the birds that did enter the wind farm, all species showed very strong avoidance close to individual turbines (micro-avoidance). Figures 18 and 19 demonstrate that gulls are far less inclined to avoid wind farms than most other species, and regularly pass between individual turbines without obvious directional changes. This corresponds with findings at Horns Rev, where gulls ignored the turbines or even were more abundant around them, possibly being attracted to potential feeding opportunities near maintenance vessels or in turbulent waters, the lee side of the monopiles (Petersen et al. 2006).
Monitoring surveys of operational offshore turbines in UK waters have also shown that lesser black-backed gulls show no obvious displacement effects. At North Hoyle post-construction monitoring in 2006/07, there was no evidence of change in density or distribution between construction and operational phases for any gull species, including lesser black-backed gull. At Kentish Flats, gulls in general seemed not to be influenced by the wind farm and certainly continued to use it after construction in 2004/05. There were no statistically significant changes in gull abundance at the wind farm and buffer. Although there was an indication that lesser black-backed gull may have declined slightly, herring gull may have increased slightly, and there was little effect upon common gull. These differences may be due to foraging strategies of gulls, where lesser black-backed gulls are more likely to be associated with fishing vessels. The creation of a safety zone around turbines would reduce fishing activity within the wind farm and therefore likely lesser black-backed gull numbers.
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Displacement It is therefore unlikely that displacement will take place out to the recommended precautionary 4km buffer and would realistically be confined, at worst, to the GWF turbine areas alone. The peak breeding season population estimate for the GWF site was 1,001 birds in June 2009, which represents one third of the current Alde-Ore Estuary SPA breeding population. This predicted level of impact is considered unlikely: lesser black-backed gulls forage widely and through analysis of ship-based surveys, Schwemmer and Garthe (2005) and Camphuysen et al. (2008) found a significant association between offshore distribution and commercial fisheries. This pattern was commonly observed during GWF boat-based surveys and so in the future, birds are likely to follow fishing vessels in the wider area after fishing activities are excluded from parts of the operational GWF site. No individual’s fitness is therefore likely to be significantly affected. The DTI (2006b) report also concluded that although many of the gulls feeding within the GGOWF area may be from the nearby Alde-Ore Estuary SPA, there is no evidence to suggest that there will be a loss of feeding grounds likely to cause an adverse affect on the population of lesser black-backed gull breeding within the Alde-Ore Estuary SPA.
Conclusion: No Likely Significant Effect Potential in-combination Data from aerial surveys indicate that the lesser black-backed gull is relatively evenly distributed throughout the Thames Strategic Area, effects although gulls in general were more common nearer to the coast.
As GWF and GGOWF are outwith the SPA boundary, the proportion of SPA birds potentially displaced cannot easily be calculated. Lesser black-backed gulls forage extensively and, therefore, can utilise different areas. Results of radio-tagged birds from both Orfordness within the SPA, and Texel, The Netherlands have shown that individuals have a variety of feeding strategies, including at inland sites, coastal fringes and offshore. The SPA Conservation Objectives (Table 2) also highlight the variety of habitats and food resources available to lesser black- backed gulls. It is, therefore, unlikely that any displaced birds will be lost to the population even if effects are recorded at GWF. With a variety of alternative foraging locations apparently available to individuals, no significant in-combination displacement effects are predicted.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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Collision Risk Potential Impacts Collision of a bird with the turbine rotors is almost certain to result in the death of the bird. Pathway: Potential effects on SPA The effect of an individual loss on a population is influenced by several characteristics of the affected population, notably its size, density, qualifying species 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, which includes lesser black-backed gull. Relevant Conservation Disturbance Objectives Components Risk of Likely Significant The lesser black-backed gull annual survival rate was listed as around 0.90 by Maclean et al. (2009), equating to high sensitivity. Effect (LSE) Reproduction and survival rates within the SPA may currently be low due to high levels of mammalian predation and human disturbance in at least one of the breeding colonies. Around 17% of all flights recorded were at PCH during boat-based surveys Although gulls are more manoeuvrable than divers, they are more likely to forage within or close to offshore wind farms, especially if vessels are present.
The collision risk modelling predicted that 23-33 birds would be lost each year (at 99.9% avoidance rate), which reduces to 16 during the 2009 breeding season (April to August). This would result in an increase in baseline mortality of 5.1% on the current SPA population. The highest mortality was predicted to occur in the late breeding season and subsequent migration period, and is likely to include a large proportion of adults from breeding pairs within the SPA and southeast England region, which are within the upper 80km foraging range for the species. Radio-tagged birds from Texel also show that birds that use the GWF site for feeding are also likely to come from a variety of colonies throughout northwest Europe.
The assumption that all birds that collide with turbines are from SPA would almost certainly not be the case, and it is reasonable to assume that many birds recorded in the GWF site do not breed in the SPA, and may come from southeast England and major colonies in the Netherlands and Belgium, which are within maximum foraging range. Not all birds found at breeding colonies are likely to be breeders, and although no information is available for the SPA colony, Calladine and Harris (1997) estimated that 34% of lesser black-backed gulls at the Isle of May colony in 1993, and 40% in 1994 did not breed. This was considered to be a normal period, unaffected by culling. It could therefore be concluded that only around two thirds of all SPA deaths are likely to be to breeding adults, assuming that all birds from the SPA use the site equally. Evidence on foraging behaviour of birds at the Texel colony, reported by Camphuysen (2011b), showed that non- breeders and failed breeders tend to forage more widely, and for longer periods than breeders, and therefore many birds recorded within the GWF site are likely not to be part of the SPA breeding population.
The level of impact on the current breeding SPA population is difficult to predict due to the large change in population as a result of factors unrelated to offshore foraging areas, and the uncertainty of future population sizes. Although avoidance rates in the Band et al. (2007) model are designed to take into account birds avoiding the wind farm as a whole at distance as well as avoiding individual turbines, this assumes that the habitat quality within the turbine area remains unchanged and that birds would still show the same potential activity levels as before, if the turbines were not in place. A change in habitat quality that is not directly related to the physical presence would however alter the
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Collision Risk attractiveness of the site to birds, and therefore reduce activity levels below the current baseline. This would be the case when the GWF is operational, since fishing vessels will be excluded from the turbine areas, and an important food resource (fish discards) will be reduced. Evidence shows that lesser black-backed gull flocks are often associated with trawlers. Lower fishing activity levels, not directly due to turbine presence, would therefore reduce future collision risks by moving foraging activity to outside of the wind farm. It is therefore considered that collision risk in the future could pose a lower impact on the SPA population than predicted through modelling. The confidence level of these predictions is however low, and therefore, the effects on the ‘Disturbance’ component of the Conservation Objectives would likely require investigation in an AA.
Conclusion: Likely Significant Effect Potential in-combination Estimates of lesser black-backed gull mortality at other offshore wind farm sites within the upper 80km foraging range of the species ranged effects from 0.5 at Thanet, to approximately 12 at GGOWF (converted to 99.9% avoidance rate). Preliminary CRM for the East Anglia ONE estimated 3.3 collisions per annum (converted to 99.9% avoidance) when turbines are 90% operational. It is not known where these birds have originated from, although it is possible that birds may have flown from a number of colonies in Essex, Greater London or Kent, as well as the Netherlands, Denmark and Germany.
During the Seabird 2000 monitoring programme, the regional breeding population was estimated as being 7,381 by Mitchell et al. (2004), which includes coastal colonies in Suffolk, Essex, Greater London and Kent. Orforndness, within the SPA, accounted for 5,500 pairs at that time, with 750 in Lowestoft. Therefore, an unknown proportion of birds occurring during the breeding season may have originated in the Alde-Ore Estuary SPA (Mitchell et al. 2004. Lower peak counts occurring during the winter months are more likely to involve birds from colonies outwith the Thames Strategic Area.
It is likely that an unknown proportion will have originated from other colonies in Norfolk, East Sussex and from major concentrations in western Europe, all of which are within foraging range. The possible provenance of all birds recorded found within the study area should be considered in an AA, in relation to collision risk effects.
Conclusion: Likely Significant Effect Qualification for AA consideration? YES
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Barrier Effects Potential Impacts Individual turbines or the offshore wind farm as a whole may present a barrier to the movement of birds, restricting or displacing birds from Pathway: much larger areas. Potential effects on SPA 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 qualifying species obstacles, this may result in greater energy expenditure. By implication, this will reduce the efficiency with which they accumulate reserves, potentially affecting their survival or later breeding success.
Breeding birds may regularly make foraging trips away from the SPA through the development site Relevant Conservation Disturbance Objectives Components Risk of Likely Significant Observations of onshore turbines at the East Dam (Zeebrugge) and Maasvlakte (Rotterdam) indicate that lesser black–backed gull fly Effect (LSE) between turbines to and from their breeding colonies and marine feeding areas (Everaert et al. 2002). Gulls were rated as being of ‘Low’ sensitivity to barrier effects by Maclean et al. (2009), and are considered among the most manoeuvrable of species by Garthe and Hüppop (2004).
There is no evidence to suggest that there is a regular foraging route between breeding colonies and particular foraging areas via the offshore wind farm area. It is, therefore, concluded that there will be no barrier effects in the context of the SPA.
Conclusion: No Likely Significant Effect Potential in-combination Only the GGOWF reported a possible barrier effect on lesser black-backed gull, which is expected since the site lies within foraging range of effects the breeding colonies in the SPA. Although the species is highly manoeuvrable and likely to pass between turbines, 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 turbine layouts of the two sites however, the adjacent 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.
There is however no evidence that GWF and GGOWF combined will create a significant barrier to movement. Other offshore wind farms within potential foraging range are each separated by several kilometres of open sea and there is no continuous barrier in the context of the SPA. No barrier effects are predicted.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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c) Potential impacts on gannet
Collision Risk Potential Impacts Collision of a bird with the turbine rotors is almost certain to result in the death of the bird. Pathway: Potential effects on SPA The effect of an individual loss on a population is influenced by several characteristics of the affected population, notably its size, density, qualifying species 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, which includes gannet. Relevant Conservation Maintain the population in favourable condition Objectives Risk of Likely Significant Garthe and Hüppop (2004) suggest that gannets predominantly fly between 10 and 20m and generally would therefore not likely be at risk Effect (LSE) 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. Nevertheless, 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, and therefore due to a combination of macro avoidance, micro avoidance (Krijgsveld et al. 2010 reported that gannets also showed very strong avoidance of individual turbines) and low flight altitudes, collision rates are likely to be very low, and realistically avoidance would be at least 99.5% as recommended by Maclean et al. (2009). Based on this rate, the GWF was predicted to account for at most 23-28 collisions each year. It is important to note that this is a ‘worst-case’ estimate, based on precautionary model assumptions (e.g. maintenance of density throughout period of time active).
This would result in an increase in baseline mortality of 1.8-2.2% (using an adult survival rate of 0.92, as per Wanless et al. 2006) over the current Flamborough Head and Bempton Cliffs SPA population. A significant level of impact on the breeding Flamborough Head and Bempton Cliffs SPA is however 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 (Dudgeon ES, 2009), 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.
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 just under 300km from the SPA and barely within the mean maximum foraging range (Langston, 2010). Evidence from satellite-tagged birds at Bempton Cliffs showed that 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. Birds found within the GWF site during the breeding season are therefore more likely to be mainly wandering non-breeders and sub-adults not attached to this SPA. Breeding birds found in the GWF that originate from the SPA are only likely to pass through once or twice per season on migration, particularly during autumn, and therefore are at negligible risk from collision.
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Collision Risk
When considering the GWF population as part of the south and eastern British breeding population, the collision rate would result in an additional mortality of 0.2-0.3%, which is likely to be a more realistic level of impact (and does not account for any non-breeders).
Conclusion: No Likely Significant Effect Potential in-combination The total cumulative annual mortality predicted from sites where CRM figures were available rose to 273-278 birds for all east coast offshore effects wind farms. This equates to an increase in baseline mortality of 21.7-22.1% on the Flamborough Head and Bempton Cliffs SPA breeding population, a 2.6% increase on the east coast Britain population, and a 0.8% increase on the national breeding population. While not accounting for sites where quantitative information was not available (although not likely to significantly contribute to mortality rates), this mortality level is likely to be a very conservative estimate, with CRM methods in general for each offshore wind farm site using ‘worst-case’ scenarios of turbine layout, coupled with the main assumptions of the density-based models, which are by nature precautionary.
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. 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 (as witnessed at GWF – Figures 16 and 17), where numbers passing through the Dover Strait reach up to 892,000 individuals (Stienen et al. 2007). It is likely that at least a proportion of the overall passage and wintering gannet populations 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.
Using Wetland International’s (2006) scaling method, the total Flamborough Head and Bempton Cliffs SPA population would be 23,577 individuals (14.5-14.7% increase in baseline mortality), with the total south and east North Sea population of 198,360 individuals (1.7% increase) and the total British population of 655,638 individuals (0.5% increase). As the Flamborough Head and Bempton Cliffs SPA population is 11.9% of the south and east North Sea population, if mortality is roughly even for all colonies (as some colonies are nearer particular offshore wind farms than others), then 32-33 collisions each year would be from the SPA. This is an increase in background mortality rate of 1.7% of the total SPA population. In reality, mortality rates are likely to be higher for colonies closer to offshore wind farms, which includes a number from the Wash Strategic Area around Flamborough Head and Bempton Cliffs SPA. However, evidence from tagged birds at Bempton Cliffs (Figure 14) shows that breeding individuals are likely to be confined to waters closer to the colony 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.
As an example, in the Triton Knoll Technical Report (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
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Collision Risk 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.
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).
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. From Figure 14 it is evident that Westermost Rough and Humber Gateway would be within that distance, as would part of Triton Knoll. The cumulative mortality for these three sites totals 69 birds (with the first two contributing <1 collision per year combined). This results in a 3.6% increase in baseline mortality rate of the total SPA population. As witnessed 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. In general, offshore wind farm sites reported greatest numbers during migratory periods, when the North Sea population swells to 892,000 individuals, and therefore Flamborough Head and Bempton Cliffs SPA birds will only form a very small part of this total of birds on migration down the east coast. It can be reasonably concluded that the annual number of collisions of birds from the Flamborough Head and Bempton Cliffs SPA is likely to be low, and insignificant compared to the current baseline mortality.
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. 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, and so the GWF will not contribute significantly to cumulative mortality on gannets.
Conclusion: No Likely Significant Effect Qualification for AA consideration? NO
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7 DISCUSSION
a) Red-throated diver
7.1 From an assessment of the data available, The HRA Screening Assessment identified no likely significant effects on the Outer Thames SPA as a result of impacts that may arise from the development of GWF, either alone or in-combination with other offshore wind farms and activities. It can be concluded that for each phase of the project the likely impacts are considered to be so minimal that an AA is not required to determined whether the Conservation Objectives of the Outer Thames SPA would be undermined.
7.2 The proposed GWF turbine areas are not within the SPA boundary, and so no habitat will be lost through turbine construction. Short-term loss of habitat within the SPA due to installation of the export cables will not be significant, due to the relatively small extent of the area affected and the likely rapid recolonisation of prey fauna in response to changes in habitat.
7.3 The GWF It is also located of sufficient distance from the SPA so that there will be no direct disturbance-displacement effects on birds within the SPA. It is recognised that SPA-associated birds may use the GWF area for foraging or loafing in unknown numbers for an unknown proportion of time, although results of aerial and boat-based surveys show that the site is sub- optimal habitat for the species, being of greater depth and further offshore than normally favoured.
7.4 Although the population of red-throated diver found in the whole GWF survey area was estimated to be of importance compared to the SPA population (3.1%), the peak winter numbers found within the area of GWF and 4km buffer zone were only 1.7% of the SPA population, assuming an unlikely worst-case that all birds are from the SPA. In addition, the estimated density of birds was generally well below densities within the SPA boundary. The possible displacement of some birds (<1%) from the GWF area is, therefore, not likely to significantly add to densities of birds in adjacent habitat and no significant losses to the population are expected to occur through additional mortality.
7.5 Due to the low-flying nature of red-throated diver, very low collision risk mortality levels have been predicted, even if birds are disturbed by construction vessels.
7.6 These conclusions are in agreement with the AA conducted in relation to possible impacts of the GGOWF on red-throated diver (DTI, 2006b). That assessment was undertaken in response to the JNCC’s concern that there would be potential cumulative impacts from the GGOWF and other developments (although not including GWF) in the Thames Estuary on the integrity of the Outer Thames SPA (at that point the proposed Greater Thames Estuary pSPA) on the red- throated diver population. Although an AA was undertaken, it was noted that “the Greater Gabbard Offshore Wind Farm is outwith the current draft boundaries of the pSPA and a Screening Assessment could have been undertaken to determine the likely significant effects on red-throated diver prior to considering undertaking an Appropriate Assessment”.
7.7 The GWF AA, therefore, addressed the “in-combination” effects on the SPA. It concluded that the GGOWF would not have an adverse effect on the integrity of the SPA, either alone or in- combination with other projects. Among the reasons given were:
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• Relatively few divers were recorded within the proposed GGOWF location.
• The evidence suggests that the flight height of divers is largely below 20m, i.e. below turbine blade-swept height, and, therefore, effects of cumulative collision from all offshore wind farms would not be significant.
• Effects due to displacement may be cumulative. Approximately 5.6-5.9% of the SPA may be impacted if all divers avoid all the offshore wind farm locations. However, there is no evidence to suggest that all divers displaced will die. It was concluded by DTI (2006b) that other suitable habitat is available for use by displaced divers.
• All proposed offshore wind farms are each separated by several kilometres of open sea and there is no continuous barrier in the context of the SPA; and
• With respect to cumulative impacts from “other activities”: these have been in place and been ongoing for many years and yet the large population of red-throated diver still exists in the Thames Estuary.
7.8 The addition of the GWF area does not significantly contribute to the predicted magnitude of effects on the red-throated diver SPA population, and so it can be reasonably concluded that no LSE will result.
b) Lesser black-backed gull
7.9 The HRA Screening Assessment identified likely significant effects on the Alde-Ore Estuary SPA as a result of impacts that may arise from the development of GWF.
7.10 The lesser black-backed gull breeding colonies at Orfordness and Havergate Island within the Alde-Ore SPA are around 25km from the proposed development. As the species is opportunistic and ranges widely to forage, it is not anticipated that factors such as direct habitat loss, disturbance-displacement and barrier effects would be significant. Lesser black-backed gull is rated as being of “Low” sensitivity to disturbance, and “Very Low” sensitivity to habitat loss by Maclean et al. (2009).
7.11 It is possible that a significant increase in mortality over the background rate due to collisions with turbines may occur, particularly as large declines in breeding pairs have been recorded since the SPA citation date. A precautionary approach suggests that at this screening stage, the potential for adverse effects on the integrity of the lesser black-backed gull SPA population through increases in mortality due to increased collision risk cannot be ruled out. In DTI’s (2006b) AA, the impacts that are suspected as being likely to cause a significant impact on the Alde-Ore Estuary SPA Conservation Objectives were also limited to the potential increases in mortality of lesser black-backed gull as a result of collision risk.
7.12 It is recommended that if an AA is requested, it should be limited to a consideration of the effects of collision risk mortality on the integrity of the SPA population and the ‘Disturbance’ component of the Conservation Objective (Table 3). This will primarily involve (i) establishing whether or not a significant portion of these birds originate from the Alde-Ore Estuary SPA breeding population, and (ii) ascertaining whether the additional mortality of SPA birds caused by collisions will prevent favourable status of the SPA population being maintained/attained.
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c) Gannet
7.13 The HRA Screening Assessment did not identify any likely significant effects on the Flamborough Head and Bempton Cliffs SPA as a result of impacts that may arise from the development of GWF, in particular relating to additional mortality due to collisions with turbines.
7.14 As the GWF site is beyond regular foraging range of any colony, most birds present, particularly in the main breeding season, are likely to be non-breeders or sub-adults that are not part of any breeding population, including Flamborough Head and Bempton Cliffs SPA.
7.15 Mortality rates when considering the GWF site alone resulted in an increase in baseline mortality on the SPA breeding population of 1.8-2.2%, which is considered very unlikely due to the large population in Britain and northwest Europe in general, and the wide-ranging nature of the species. When considering these populations, the actual level of impact on the SPA is likely to be much less than 1%.
7.16 When all proposed, in-construction or operational Round 1 and 2 offshore wind farms in eastern Britain are considered, the increase in baseline mortality on the SPA population grows to around 22%, although only 2.6% for the eastern Britain population, and <1% on the entire British population. This latter magnitude is considered to be more realistic, when accounting for the number of non-breeders found in British waters, the restricted foraging range of breeding birds in summer months, and the migratory peaks in numbers witnessed at other offshore wind farms. In conclusion, it is unlikely that the cumulative mortality effect of wind farms along the east coast will significantly affect the Flamborough Head and Bempton Cliffs SPA population, and that GWF would likely contribute only a very small, insignificant proportion to overall mortality rates as it is outside of the regular foraging range of all gannet colonies.
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