Potential conflicts between bird conservation and wind power production in the Baltic Sea Background Report, HELCOM-VASAB WG Meeting on Marine Spatial Planning, January 29-30, 2012

1. Introduction

As a response to climate change, there is a global incentive to find new ways to increase the production of energy from renewable sources. The EU has set the target to achieve 20 % energy consumption from renewable sources by 2020.1 Consequently, wind power production in the EU countries, including the Baltic Sea, has grown dramatically during the past years. In the end of 2011, there were approximately 540 turbines in place in the offshore waters of Denmark, Germany, Sweden and Finland, producing nearly 1,250 MW (EWEA 2012).

The offshore shallow banks that are optimal for wind power construction are often sites that are preferred by many species of birds for breeding, feeding, roosting and/or resting, including the migratory birds that stop there when flying across (Larsen and Guillemette 2007). Hence, possible conflicts at these sites emerge between nature protection and energy production. The realization of such conflicts has led to the emergence of a large number of studies that have looked at potential impacts of wind farms on birds. A Google Scholar search command "wind farm" AND "bird" produces more than 4,000 hits (November 29, 2012), including case studies, research and popular articles, management oriented documents, impact assessment reports or other reports.

The aim of this report is to give an overview of what is currently known of the potential adverse impacts of wind farms on birds in the Baltic Sea context, based on the existing literature. The report has been prepared as a background document for discussion in the HELCOM-VASAB Working Group Meeting on Marine Spatial Planning, to be held on January 29-30, 2012 in Riga, Latvia.

In order to reach a favourable conservation status of Baltic Sea biodiversity HELCOM has in its Baltic Sea Action Plan adopted three Ecological Objectives: natural marine and coastal landscapes, thriving and balanced communities of plants and animals, and viable populations of species. To make these objectives operational and to assess how they have been achieved, targets and indicators have been developed. The CORESET expert group on biodiversity indicators (including a working group on waterbirds) is developing indicators with targets or boundaries for good environmental status that will enable classification of the environmental status into different status quality classes.

1 Directive 2009/28/EC of the European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC) Figure 1. Map of underwater sandbanks, Important Bird Areas and wind farms. The map will be updated as new information on wind farms becomes available. The VASAB Secretariat in cooperation with the BASREC project are working on a new compilation.

2. Baltic Sea is an important area for birds

2.1 Baltic Sea as a flyway and staging area for migratory birds

The Baltic Sea is crossed by millions of migratory birds twice a year. In the fall water birds fly in masses from their Arctic breeding grounds via the Estonian coast and Belarus towards the Southwestern Baltic Sea and still further to reach their southern wintering grounds (Hario et al. 2006). Most migrants fly through the western side of the Gulf of Bothnia, and in the Gulf of Finland the most intense migration occurs on the southern side of the Gulf of Finland. In the spring another mass migration can be observed via the Curonian Spit and the southern coasts of the Baltic Sea, following the coastline of either Estonia or Finland (depending on the winds) and via Russia towards the Arctic (Figure 2). For many ducks, geese and swans, Western Europe is the final destination but for others, it is a stepping stone on a journey eventually concluding at wintering grounds in Africa (BirdLife International, A).

For terrestrial birds, migratory routes in Finland are concentrated in Åland, Hanko peninsula and Porkkala, which impose a collision risk at these sites. Such important bottleneck areas are also found in the Southern tip of Öland Island (Sweden) and at Falsterbo (Southwestern tip of Sweden).

In order to make the long trip, birds stop at staging sites (sites along the migration corridors that are suitable for feeding) which are essential for successful migration (Myers 1983, HELCOM 2011). In the Baltic Sea such sites include shallow offshore banks of the German Coast, south of Gotland and at the Gulf of Riga, which also serve as important wintering areas (communication with Tero Toivanen, BirdLife Finland, December 5, 2012).

Figure 2. A coarse approximation of migratory routes of water birds (Arctic ducks, geese and Gaviiformes), see text (drawn by Tero Toivanen, BirdLife Finland). It should be noted that this map is an oversimplification as migratory routes are species specific.

Many species of birds migrate along broadly similar, well-established routes known as flyways. The flyways often follow geographic patterns (such as coastlines) and avoid barriers (such as mountains or wide offshore areas), and birds hence do not necessarily take the shortest route (Berthold 2001; Alerstam 2001). Sometimes there is heterogeneity among migration routes within a population, as has been shown to be the case for example for the Arctic tern (Sterna paradisaea) (Egevang et al. 2010).

General pathways can be sketched for oversimplification to describe some of the general movement patterns. Two of such oversimplifications, the East Atlantic flyway and the Mediterranean/Black Sea flyway (the latter only in part) cross the Baltic Sea.

The East Atlantic flyway (Figure 3) is a highly summarized map which applies to some waders. This flyway links the Arctic breeding grounds of nearly 300 species of birds with wintering grounds in Western Europe or West Africa (BirdLife International, A). It should be noted that migratory strategies are species specific and influenced by many factors. Hence, it is incorrect to use the map as such, but all migratory paths should be taken into account as individual entities depending on the species.

Each autumn, a large number of birds fly in the north-south direction. It is important that the birds have staging areas along the way, e.g. in the Baltic Sea, where they can feed and gain energy to continue their flight. These sites are often designated as IBA areas (see below). Seven species that occur along the East Atlantic Flyway are now regarded as globally threatened, including the Aquatic Warbler (Acrocephalus paludicola) (VU) and Steller's Eider (Polysticta stelleri) (VU) (BirdLife International, A.). The Aquatic Warbler breeds in fen mires in the Pomeranian region between Poland and Germany (Tanneberger et al. 2010). Non-breeding populations of Steller’s Eider can be found in three locations in the Baltic Sea (in Gotland, coastal areas in Lithuania and Latvia and near Kuressaare in Estonia) (BirdLife International, C.). Overall, it has been estimated that 37% of the wader populations using the East-Atlantic flyway route are in decline (BirdLife International, A.).

The Mediterranean/Black Sea flyway (Figure 4), covering almost 50 million km2, extends from the southern tip of Africa all the way to Siberia, and covers parts of the South-Eastern Baltic Sea, including the Baltic countries up to their coasts and an eastern stretch of the Gulf of Finland. Approximately 2 billion passerines and near-passerines, 2.5 million ducks and 2 million raptors (consisting of more than 300 species) migrate this route from their breeding grounds in Europe or central and western Asia to their wintering grounds in tropical Africa (BirdLife International, B.).

The climate change has advanced the timing of migration in several species, including Northern European and Baltic Sea bird species. Long-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants, and the shift can be observed in all phases of migration (Jonzén et al. 2006). This has led to the mismatch occurring between arrival and food availability in many cases, which may in turn cause population declines (Both et al. 2006 and 2010; Møller et al. 2008; Saino et al. 2011; Sparks et al. 2005). Our knowledge on the timing and routes of bird migration is constantly improving as new study technologies become available (Bridge et al. 2011). Figure 3. The East-Atlantic flyway (BirdLife International, A).

Figure 4. The Mediterranean/Black Sea flyway (BirdLife International, B).

2.2 Baltic Sea as a breeding and wintering area

There are 57 species of birds that breed at the Baltic Sea area or in its immediate vicinity. Most are waterbirds, such as grebes (Podiceps auritus and P. cristatus), fish eating ducks (Mergus albellus, M. serrator and M. Merganser), diving ducks (Aythya fulifula, A. marila, Somateria mollissima, Melanitta fusca, Bucephala clangula), surface feeding ducks (Anas strepera, A. platyrhynchos, A. clypeata, A. fuligula and A. marila), geese (Branta leucopsis and Anser anser), swans (Cygnus olor), terns (e.g. Sterna spp., Rissa tridactyla, Sternula albifrons, Hydroprogne caspia etc.), gulls (Larus spp.), auks (Uria aalge, Alca torda, Cepphus grylle), or waders (e.g. Vanellus vanellus, Haematopus ostralegus, Recurvirostra avosetta and Limosa limosa). Also two species of eagles (Haliaeetus albicilla and Pandion haliaetus) are Baltic breeders as well as some passerines including swallows (Riparia riparia, Anthus petrosus and A. pratensis), Wagtail (Motacilla alba) and Wheatear (Oenanthe oenanthe) (HELCOM 2011).

Most of the above listed birds are migratory species but some of them are residential and in addition to breeding at the Baltic, they also use the area as an overwintering ground. For example, the long- tailed duck (Clangula hyemalis), common eider (Somateria mollissima), white-winged scoter (Melanitta fusca) and black scoter (Melanitta nigra) spend their winters in the area. Shallow and ice- free coasts of southern and southwestern Baltic Sea, mainly the German coast outside the Oder delta, but also Kattegat, southern Gotland and Bay of Riga, are the most important wintering areas.

3. Bird population status and trends in the Baltic Sea Despite the existing legislation and conservation efforts, many Baltic Sea species of birds are declining (Papazoglou et al. 2004; HELCOM 2011). Reasons for the declines include habitat destruction (which is the predominant threat for coastal and marine bird species), by-catch, contaminants (such as hazardous substances), plastic waste (litter), oil spills, predators and invasive species, hunting, offshore construction (especially wind farms) and epidemics (HELCOM 2011).

HELCOM is developing a Red List for Baltic Sea birds to assess the extinction risk of birds from a regional (biogeographic) point of view. The Red List classification system is based on the IUCN methods, categories and criteria (IUCN 2001). To date an Interim Report of the Baltic Breeding Birds has been published. The Red List for the Baltic Sea Wintering Birds is currently under preparation. It had previously been discussed in the Red List expert groups to prepare a classification of migratory birds resting temporarily in the Baltic Sea area (e.g. some arctic birds), but the process has been put on hold.

The Red List of the Baltic Breeding Birds includes species that are breeding in the Baltic Sea area having a distinct relationship to the marine or coastal environment. According to the interim results (HELCOM 2011) one species, the Gull-billed Tern (Gelochelidon nilotica), is considered as Regionally Extinct (RE). The Kentish Plover (Charadrius alexandrines), which formerly was a regular breeder in Denmark, Sweden and Germany, is currently classified Critically Endangered (CR). The category Endangered (EN) comprises of 4 species: Dunlin (Calidris alpine schinzii), Terek Sandpiper (Xenus cinereus), Mediterranean Gull (Larus melanocephalus) and Black-legged Kittiwake (Rissa tridactyla). Eight taxa classify for the category Vulnerable (VU): Slavonian Grebe (Podiceps auritus), Greater Scaup (Aytya marila), Common Eider (Somateria mollissima), Velvet Scoter (Melanitta fusca), Ruff (Philomachus pugnax), Turnstone (Arenaria interpres), Lesser Black-backed Gull (Larus fuscus fuscus) and the Caspian Tern (Hydroprogne caspia). The category Near Threatened (NT) comprises 8 taxa, and the category Least Concern (LC) 35).

Since the beginning of the 1990s the overall population of wintering waterbirds in the Baltic Sea has reduced by 30 %. It seems that the majority of the wintering waterbird species are decreasing as 10 out of the 20 assessed species had a declining trend, whereas for only 7 species the populations have increased during the past 16 years (Skov et al. 2011). The species with most notable declining trends were Long-tailed duck (Clangula hyemalis) and Velvet scoter (Melanitta fusca). There is no clear consensus on what are the main reasons for the declines for every species, but the oiling is the main pressure for Long-tailed duck (communication with the HELCOM CORESET expert team on waterbirds). In general, the following pressures are recognized: eutrophication, climate change, oceanographic oscillations, by-catch, hunting, oil, hazardous substances, fishing pressure, fisheries discards, predation, coastal development, wind energy, and sand- and gravel extraction. The Red List for the Baltic Sea Wintering Birds is currently under preparation (Skov et al. 2011). 4. Conservation of Baltic birds in the legal framework

4.1 Conventions and treaties

Global and European conventions and treaties have been formed in order to protect migratory species (including birds) throughout their migratory range. These include the Bonn Convention, Bern Convention, Ramsar Convention and the African-Eurasian Migratory Waterbird Agreement.

The Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention), concluded under the United Nations Environment Programme (UNEP), is the only global convention focused on terrestrial, aquatic and avian migratory species and their conservation throughout their range. All coastal Baltic Sea states (except Russia) are parties to the Bonn Convention. The migratory species threatened with extinction are listed on Appendix I and the migratory species that need or would significantly benefit from international co-operation are listed in Appendix II of the Convention.

The African-Eurasian Migratory Waterbird Agreement (AEWA) is an intergovernmental treaty developed under the framework of the Bonn Convention and administered by the UNEP. AEWA is dedicated to the conservation of migratory waterbirds and their habitats across the globe covering 255 species of birds ecologically dependent on wetlands for at least part of their annual cycle, including many species of divers, grebes, cormorants, ducks, swans, geese, waders, gulls, terns and auks. All AEWA species cross international boundaries during their migrations and require good quality habitat for breeding as well as a network of suitable sites to support their annual journeys.

At the European level, the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) came into force in 1982. The Bern Convention aims to promote European cooperation in the field of conservation of wild flora and fauna and their natural habitats. The strictly protected species of birds are listed in its Appendix II and protected fauna in Appendix III. To implement the Bern Convention in Europe, the European Community adopted Council Directive 2009/147/EEC on the Conservation of Wild Birds (The Birds Directive) in 2009 (Anon. 2009) (which replaces the Council Directive 79/409/EEC) and Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora (The Habitats Directive), in 1992 (Anon. 1992). The Birds Directive lists in its Annex I those bird species that shall be the subject of special conservation measures concerning their habitat in order to ensure their survival and reproduction in their area of distribution, whereas the Annex II lists the species that may be hunted under national legislation.

The Convention on Wetlands (Ramsar Convention), which came into force in 1975, is the only global environmental treaty that deals with conservation of wetlands and their resources. Wetlands are extremely important for waterbirds such as swans, ducks and geese, and waders that use wetlands during the majority of their lifetime. At least 12% of all Globally Threatened Birds, (146 species) depend on wetlands and 69% of all European IBAs contain wetlands (source: BirdLife International website). 4 .2 Existing conservation sites and networks

Article 4 of the Birds Directive requires Member States to classify the most suitable territories in number and size as Special Protection Areas (SPAs) for those species requiring special conservation measures: these are the species listed in Annex I and all migratory species.

The Pan-European Biological and Landscape Diversity Strategy (PEBLDS) was endorsed by 54 countries in 1995 as a follow-up of the Rio Earth Summit and the adoption of the United Nations Convention on Biological Diversity (CBD). One of the long-term objectives of the Strategy is the establishment of a Pan-European Ecological Network (PEEN) to conserve ecosystems, habitats, species and landscapes that are of European importance.

The Emerald Network is an ecological network made up of areas of special conservation interest. Launched by the Council of Europe as part of its work under the Bern Convention, the Network contributes to the setting-up of the PEEN and facilitates the establishment of national networks of protected areas. As the European Union is a Contracting Party to the Bern Convention, Natura 2000 (including Special Protection Areas, SPAs, and Sites of Community Importance, SCIs) is considered to be the EU contribution to the Emerald Network.

BirdLife Europe has designated a network of Important European Bird Areas (IBAs) which are sites with specific bird conservation significance. The IBAs are identified as the most suitable sites for SPA classification required by the Birds Directive. Important Bird Areas are selected on the basis of internationally agreed standard criteria taking into account the Emerald Network under the Bern Convention, the Helsinki Convention, the Barcelona Convention, as well as, the Birds Directive of the European Union. At the Baltic Sea, the IBA areas are mainly distributed along the coast but also a few open sea areas exist (Figure 5). IBAs are selected based on that they either hold species with global conservation importance or have exceptionally high numbers of migratory or congregatory species. These are in essence those areas that migratory birds use for resting and feeding.

“Migration bottlenecks” are geographically limited areas such as straits or headlands through which high concentrations of migratory birds pass and where they stop to feed and rest. Sometimes these areas are also called migratory hotspots (Baisner et al. 2010). These areas hence have high conservation significance (Myers 1983). Two examples of Baltic bottlenecks are the Curonian Spit between Kaliningrad and Klaipeda and the eastern Gulf of Finland. The Lithuanian side of the Curonian spit is classified as an IBA area.

4.3 Directives and national legislation regulating wind farm planning and construction in the Baltic Sea

Environmental Impact Assessments (EIA) and Strategic Environmental Assessments (SEA) should be conducted for certain public or private projects, plans and programmes in the EU territory. It is set in the EIA Directive (85/337/EEC) (Anon. 1985) that “environmental impact assessment shall identify, describe and assess in an appropriate manner, in the light of each individual case, the direct and indirect effects of a project on human beings, fauna and flora.” One of the aims of the SEA Directive (2001/42/EC) (Anon. 2001), on the other hand, is to point out possibilities for the member states to harmonize and to connect different environmental assessment procedures (Schmidt et al. 2005). The 8 SEA Directive states that when required, an environmental report should be prepared containing relevant information as set out in this Directive, identifying, describing and evaluating the likely significant environmental effects of implementing the plan or programme, and reasonable alternatives taking into account the objectives and the geographical scope of the plan or programme.

It is recognized that individually a wind farm (or any action) may have minor effects on the environment but collectively these may be significant and potentially greater than the sum of the individual parts acting alone. Hence, EU legislation requires a cumulative impact assessment (CIA) as part of the Environmental Impact Assessment. It is recommended, that when making CIAs that all species of birds for which the area is important and whose characteristics make them especially vulnerable (e.g. species flying at turbine height, important in terms of the protected area, or with low reproductive output (King et al. 2009) in addition to the Annex I species of birds from the Birds Directive should be included (Masden et al. 2009).

Countries may also have national regulations concerning offshore wind power construction. E.g. Germany has an Ordinance on Offshore Installations Seaward of the Limit of the German Territorial Sea in place since 1997, which requires EIA in the German EEZ.

Figure 5. Locations of the Important Bird Areas (IBAs) in the Baltic Sea (BirdLife Europe). 5. Potential impacts of wind farms on bird populations

5.1. Offshore wind farms pose a variety of potential adverse impacts on birds

The majority of the scientific studies to date have focused on onshore wind farm effects, but as offshore plants are becoming a more frequent phenomenon, case studies investigating effects/impacts at these sites are increasingly starting to emerge. In the Baltic Sea case studies looking at wind farm impacts on birds have been done in the Danish (Tunø Knob, Horns Rev and Nysted) (Desholm and Kahlert 2005; Blew et al. 2008; Larsen and Guillemette 2007), Swedish (Kalmar Sound) (Petterson 2005) and German (FINO, Helgoland) (Hüppop et al. 2006) waters. Outside the Baltic Sea area, existing studies of effects of wind farms on birds (mainly from onshore installations and turbine types) comes from the US (Altamont Pass), Spain (Lekuona and Ursúa 2007), Britain (Drewitt and Langston 2006) and the Netherlands (Dirkesen et al. 2007). Modeling studies, on the other hand, have provided valuable insights at the species-specific level (e.g. Masden et al. 2010; Garthe and Hüppop 2004; Desholm 2009).

It has been hypothesized that offshore wind farms can potentially affect birds to a larger extent than onshore wind farms because the areas where the wind farms are built are rich in large bird species and generally more sensitive to disturbance, and because offshore turbines are usually taller and larger than the ones on land (Exo et al. 2003; Garthe and Hüppop 2004).

Several authors group the potential adverse effects of wind farms on birds into three broad categories: (1) disturbance, (2) habitat modification or loss, and (3) collisions with turbines causing direct mortality (Stewart et al. 2007; Masden et al. 2010; Drewitt and Langston 2006; Langston and Pullan 2003). In this section the possible adverse effects are briefly reviewed. Depending on the species and location different factors may be most important. It is also briefly explained why assessments with long time series and with an appropriate design (taking into account cumulative effects, and applying Before-after-control-impact assessments) are needed in order to increase the knowledge for making appropriate conservation and management decisions.

5.1 Disturbance effects - avoidance and barrier effect

Wind farms can disturb birds through a barrier effect which may lead to avoidance. Disturbance can also refer to displacement of birds from the area due to e.g. visual intrusion, i.e. causing habitat loss (see section 6.2). Disturbance caused by wind farms varies greatly, but there is evidence that disturbance effects can in some cases lead to serious population level consequences (Drewitt and Langston 2006; Pearce-Higgins et al. 2007).

Sometimes wind farms can act as barriers for birds. For example, if turbines are installed at sites which birds pass on a daily basis (e.g. for breeding, feeding or roosting), it can lead to the disruption of these ecological linkages. A problem may also arise under circumstances where the wind farm structures are installed at an important migratory route, especially for birds that are flying at rotor height altitude (Masden et al. 2009 ). In such cases birds risk to collide with the structures (see below) or they may start to avoid the structures (avoidance behavior) by veering off. The avoidance behavior in turn may cause extra energy costs especially for species commuting daily within a region, for instance between foraging grounds and roosting or nest sites (Masden et al. 2009; 2010). Such 10 disturbance effects can occur over a long time period, and may take place during the construction and maintenance (involving maintenance visits to the site when the wind farm is in operation) phases (Drewitt and Langston 2006; Exo et al. 2003).

Barrier effects with avoidance behavior have been documented at offshore areas for water birds. For example, Petterson (2005) reported a barrier effect for waterfowl in the Kalmar Sound, Sweden. Waterfowl, including eider, migrates through this area twice a year, and it was observed that they extended their migration path eastward in spring migration. However, the extension to their overall migration route was estimated to be only 0.2-0.4 %. The existence of barrier effect was also shown to occur in the Netherlands (Dirkesen et al. 2007), where it was found that a turbine row acted as a barrier for diving ducks.

In Denmark, Larsen and Guillemette (2007) showed that common eiders (Somateria mollissima) avoided wind farms at the Tunø Knob wind park by adjusting their flight path, and they found that this behavioral change was not caused by the action of the wind turbine rotors but by the presence of the turbines themselves. Their findings are in line with Madsen et al. (2009) who showed that eider avoided the Nysted wind farm, Denmark, by flying around it rather than between the turbines.

Masden et al. (2010) modeled the likely impact of wind farms on a range of breeding seabirds due to the avoidance response. They found the highest costs occurred for cormorants, and the costs were relatively high for terns due to the high daily frequency of foraging flights. They concluded that the cost of extra flight to avoid a wind farm appears less relative to other factors (such as low food abundance or weather), and that species-specific approach is essential when assessing the impacts of wind farms on breeding seabird populations to fully anticipate the effects of avoidance flights.

For example, Pearce-Higgins et al. 2007 reported significant disturbance effects of a wind farm in upland UK on large waders with population level effects. The curlew (Numenius arquata) populations declined about 40 % as a result of disturbance from wind farm construction work and snipe (Gallinago gallinago) densities more than 50 %, and neither population recovered after the construction phase. Red grouse (Lagopus lagopus scoticus) populations also declined, but recovered after the construction. In this study, it was shown that the wind farm construction phase can have greater impacts on birds than wind farm operation.

5.2 Habitat loss and modification

Habitat loss can occur if birds are displaced from areas within and surrounding wind farms due to visual intrusion and disturbance. Unfortunately, many studies on the displacement are not conclusive because of the lack of before-and-after and control-impact (BACI) assessments (Drewitt and Langston 2006).

Offshore waterbirds, such as the Long-tailed Duck (Clangula hyemalis), Velvet Scoter (Melanitta fusca) and Common Scoter (Melanitta nigra), aggregate on shallow offshore reefs where they feed on mussels during their wintering time. The few offshore reefs in the Baltic are oasis for the offshore birds which have much lower abundances in other areas during winter times. Wind farm construction and placement, including their power cables, as well as the maintenance traffic destroy mussel beds and disturb or defer birds and thus causes habitat loss of a very limited habitat type. In the wind farm construction process alterations in land-use or use of the seabed may occur. These changes can be negative (loss or decrease of some important element, e.g. food, in the habitat) or positive (e.g. increase in some prey species) (Lindebloom et al. 2011; Drewitt and Langston 2006). It is largely unknown what is the scale and nature of such changes and whether they are significant or not (Drewitt and Langston 2006).

5.3 Collision risk and mortality

Several studies have focused on examining the collision risk between birds and wind farms (e.g. Blew et al. 2008; Desholm and Kahlert 2005; Blew et al. 2008; Erickson et al. 2005; Hüppop et al. 2006; Larsen and Guillemette 2007; Krijgsveld et al. 2009). The average rates of collisions range between 0.01 to 23 birds annually (Drewitt and Langston 2006). The rates are thought to be higher for raptors than for passerines (Smallwood 2006), and collisions are more likely to occur at night or under poor weather conditions (Desholm and Kahlert 2005). There exist cases with exceptionally high rates of collision mortality such as the Altamont Pass site in California, US, and the wind park of Navarra, Northern Spain. In the Altamont Pass, which is a site with more than 5,000 turbines, bird collision rates with wind farms have been documented with long time series (since the 1990s). An early 2- year study done at this location reported 182 bird deaths in two years of which most collisions occurred with raptors (68 percent) compared to passerines (26 percent) (Orloff and Flannery 1992). Later, it has been estimated that overall 800-1,300 raptors have been killed by approximately 4,000 wind turbines at this site (Smallwood 2006).

In Navarra, Northern Spain, some species of birds were identified to be more susceptible to collision than others (Lekuona and Ursúa 2007). The species with high risk index (more than 10 %) included several species of raptors. On the contrary, passerines tended to have a low risk index (less than 9.9%).

Of the Baltic species, it has been found that the White-tailed eagle (Haliaeetus albicilla) is a sensitive species for collisions. In Smøla, in western Norway, four of the 36 satellite-tagged birds were killed by collisions with turbines in 2005-2010 (Nygård et al. 2010).

Collision risk is generally assumed to be higher in adverse weather conditions and at night (Desholm and Kahlert 2005; Krijgsveld et al. 2009). The impacts of the Utgrunden offshore wind farm on migration of waterfowl and passerines were studied in Kalmar Sound, Sweden, in 1999-2003 and 2006-2008 (Pettersson 2005 and 2011). These studies indicate that waterfowl veer off from the wind turbines and avoid them. At daytime only less than 0.5 % of birds flew between the turbines while on nights without fog the percentage was 5 % and 9 % on foggy nights. It was estimated that overall, during one year 16 song birds die out of the 500 000 that pass the area each year. For waterfowl the number of deaths is 10-15 birds annually. However, it has been suggested that more migration occurs in fair weather than with cloud or rain (Richardson 1978; Drewitt and Langston 2006).

Diurnally active local birds foraging at three selected Dutch wind farms were found to collide with wind farms, rather than nocturnal migrants (Krijgsveld et al. 2009). The reason for this was speculated to be that local birds generally pass a wind farm several times while a migrant bird passes that farm just once.

12 It has been hypothesized that the size and alignment of turbines and rotor speed and noise can influence the collision risk (Drewitt and Langston 2006; Petterson 2005), but this relationship is not fully understood (Krijgsveld et al. 2009). E.g. Barclay et al. in 2007 investigated the effects of rotor size and tower height on bird fatalities at wind energy facilities, and found that the diameter of the turbine rotor did not influence the rate of bird fatality and the height of the turbine tower had no effect on bird fatalities per turbine. A Danish study (Larsen and Guillemette 2007) found no effect of rotor movement and noise on common eiders in contrast to an earlier study (De Lucas 2004) which found.To put the bird mortality arising from collisions into a larger context, it should be kept in mind that there are several other anthropogenic causes leading to the death of nearly a billion of birds yearly (in the US), including collisions with different types of structures (buildings, powerlines, windows, vehicles etc.) as well as e.g. pollution, oil spills and by catch, and it is ultimately the cumulative impacts of all these factors combined which determines how and to what extent the population will be affected (Erickson et al. 2005).

5.4 Species sensitivity to adverse effects

The effects caused by wind farms on birds are species specific, i.e. different species react in different ways. It is often costly and time consuming to study each species separately. One way to approach this challenge is to develop priority or vulnerability indices in order to find out which species are most affected. This type of approach aims to assist in decision making as it helps to direct the resources towards the most sensitive species.

A sensitivity index was developed and applied in the German North Sea for effects of offshore wind farms on seabirds (Garthe and Hüppop 2004). The analysis took into account nine various factors (flight manoeuvrability, flight altitude, time at flight, nocturnal flight activity, sensitivity to disturbance from ships and helicopters, flexibility in habitat use, population size, adult survial rate, and European threat and conservation status). The results indicated that Black-throated diver (Gavia arctica) and red-throated diver (Gavia stellata) were most sensitive to the effects. The velvet scoter (Melanitta fusca), sandwich tern (Sterna sandvicensis) and great cormorant (Phalacrocorax carbo) were consided next sensitive after the divers. The black-legged kittiwake (Rissa tridactyla), black- headed gull (Larus ridibundus) and northern fulmar (Fulmarus glacialis) received the lowest values.

According to another index developed by Desholm (2009) birds of prey and waterbirds are most impacted by the Nysted wind farm when compared to passerines. This sensitivity index measures species abundance and demographic sensitivity (elasticity of population growth rate to changes in adult survival) and together 38 species were considered. The Common Eider (S. mollissima), which is classified as vulnerable according to the HELCOM preliminary Red List of Baltic Breeding Birds, is listed to be among the eight most impacted species.

6. The current gaps and ways of setting priorities

In terms of conservation of birds, it is essential to study whether the effects cause a decrease in the population size. Although to date it is clear that wind farms may pose a significant negative impact on bird abundance, it is still unclear whether the negative impacts cause a decline in population abundance. In other words, it can only be hypothesized how the adverse effects ultimately impact the status of birds (Stewart et al. 2007; Desholm 2006; Pearce-Higgins et al. 2012). It should be kept in mind that the effects of windfarms on birds can be positive in some cases (Wilhelmsson et al. 2010), e.g. if the wind farm creates new habitat which was the case for cormorants in a Dutch offshore windfarm (Poot et al. 2011).

Individually a wind farm may have minor effects on birds, but when all factors are combined, the effects may be significant and potentially even greater than the sum of the individual parts acting alone (Masden et al. 2009). This is why cumulative impact assessments should be conducted when necessary. In the Baltic Sea, in addition to wind farms, several other factors are affecting birds. Some of the most important pressures are considered to be by-catch, oiling, eutrophication, climate change, hunting and pollution (Skov et al. 2011).

Before-after-control-impact (BACI) assessments are important for understanding the cumulative impacts and to reveal the impacts at the population level (Drewitt and Langston 2006; Masden et al. 2009; Exo et al. 2003). In order to conduct such assessments, it is essential that enough time has passed from the construction so that long-term data series including post-construction effects are available. Only few such data sets are currently available and hence not many studies that have applied BACI assessments currently exist (Stewart et al. 2007). However, as BACI assessments always imply that the wind farms will be constructed and impacts are followed afterwards, it is essential to use the conclusions of the existing BACI assessments in the permit processes while continuing to initiate also BACI assessments at new sites.

As areas where migration routes cross the wind turbine sites are risky (in terms of potential collisions and disturbance effects), it is important to know the migratory routes of birds. Currently there is no detailed data on migratory routes in Europe available. Also, a challenge is that the existing data is often scattered at the regional level and there is often no willingness for sharing it to the public.

Prioritizing the construction of wind farms at depths of more than 25-30 m should be favored, and construction at the shallow banks which are used for breeding, feeding and staging by offshore water birds should be avoided. Sensitive species utilizing the shallow offshore banks are the Long- tailed Duck (Clangula hyemalis), Steller’s Eider (Polysticta stelleri), Velvet Scoter (Melanitta fusca), Common Scoter (Melanitta nigra) and the Red-throated Diver (Gavia stellata). The Lesser White- fronted Goose (Anser erythropus) and the Eurasian Curlew (Numenius arquata) are species classified vulnerable and near threatened according to the IUCN, respectively, and these species make use of the Baltic Sea as a staging area when migrating (personal communication with Teemu Lehtiniemi, BirdLife Finland).

Several mitigation measures have been suggested in the literature. Drewitt and Langston (2006) list several possible measures and suggest that mitigation should be applied at two levels: best-practice measures could be adopted as an industry standard and additional measures site-specifically. Strategies based on habitat management and turbine placement were seen as the most important measures by Thelander and Smallwood (2007) who estimated that adaptive management could be used to prevent 1000-2000 turbine-related bird kills per year. A spatial planning tool was developed to minimize collision risk between migrating raptors and marine wind farms (Baisner et al. 2010). This tool could be used by authorities to make informed decisions about erecting new wind farms so 14 that the collision risk for raptors can be minimized. A review of methods to monitor collisions or micro-avoidance of birds with offshore wind turbines has recently been provided (Collier et al. 2012).

According to BirdLife International (Birdlife Europe 2011), precaution should be taken when selecting sites for wind farms by avoiding locating wind farms in designated protection areas (such as IBAs, Natura 2000 sites, Ramsar sites and Emerald sites) or other areas with large concentrations of birds such as migration crossing points, or species of conservation concern. Research and monitoring should be conducted to improve the understanding of the impacts of wind farms on birds, Strategic Environmental Assessments should be undertaken by national governments (including indicative mapping of bird populations, habitats flyways and migration routes and an assessment of the wind farm plan on these), species and areas of concern should be identified and mapped, incentives for ongoing technological development are needed, and best practice should continue being shared and used by developers.

Wind power production in the Baltic Sea is growing strongly in the near future, and from the bird conservation point of view, the planners should consider the effects in the long-term (personal communication with Teemu Lehtiniemi, BirdLife Finland).

7. Acknowledgements

Special thanks to Teemu Lehtiniemi (Head of conservation and science, BirdLife Finland) for an interview and Tero Toivanen (Conservation specialist, BirdLife Finland), for providing a sketch and explanation on migratory routes, and to Aleksi Lehikoinen (Curator, Natural History Museum, University of Helsinki) for comments. Thank you also to the Library of the Finnish Museum of Natural History (University of Helsinki) for helping getting access to literature.

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Comments from BirdLife Europe

- Figure 2 is missing an important migration route in central Baltic, which follows the Saarenmaa south shore (picture attached). o Could this figure perhaps be redrawn by BirdLife? (The current map is an approximation received as a voluntarily input from BirdLife Finland). - Confusing use of ”offshore”, often just refer to any windfarm at sea (i.e. marine) o Could you please be more specific: i.e. how should the term be properly used to make the text clearer? - Sensitivity indexes. There is current work to improve the proposal by Garthe & Hueppop (2003), trying to discern sensitivity to disturbance/habitat lose and sensitivity to collision o Could you please give us the reference? - Collision rates in pp. 15, not clear if are presented per turbine or per area. o Can you please specify which part of the text you mean? - Would be good to include information on mitigation (technical) measures o The mitigation measures we are aware of are listed on pp. 15 in the paragraph starting “Several mitigation measures have been suggested in the literature. Drewitt and Langston (2006)..”. Please could you add to this list of the available techniques?

Migratory route in Central Baltic (Figure 2)

Finally, in case you're not aware, a useful webpage with information on good practice regarding windfarms: http://www.project-gpwind.eu/. 20