Seabird Monitoring in the German North Sea and 2016

Kai Borkenhagen1, Nils Guse1, Mirko Hauswirth2, Hanna Markones1, Nele Markones1, Bettina Mendel1, Henriette Schwemmer1, Stefan Garthe1

1) Research and Technology Centre West Coast (FTZ), Kiel University, Hafentörn 1, D-25761 Büsum

2) Federal Agency for Nature Conservation, , D-18581 Seabird Monitoring 2016

Introduction Seabirds, as top predators, are an important component of marine ecosystems. They are under increasing pressure from anthropogenic activities such as fishing, the development of offshore wind energy, shipping traffic, marine pollution, etc. Recording species occurrence and improving knowledge of the distribution patterns, population trends and habitat requirements is vital to effectively manage protected areas and associated seabirds. The Birds Directive (BD) and the Marine Strategy Framework Directive (MSFD) of the European Union require their member states to regularly submit reports based on data presented in this report. In addition, the data are used to develop indicators to assess the state of the environment within the framework of the regional sea conventions OSPAR and HELCOM.

The marine biodiversity monitoring programme for vertebrates is funded by the German Federal Agency for Nature Conservation (Bundesamt für Naturschutz - BfN) and carried out by the FTZ (Research and Technology Centre, Kiel University) in collaboration with the German Oceanographic Museum (Deutsches Meeresmuseum - DMM) and the Institute for Terrestrial and Aquatic Wildlife Research of the Hanover University of Veterinary Medicine Foundation (Institut für Terrestrische und Aquatische Wildtierforschung der Stiftung Tierärztliche Hochschule Hannover - ITAW).

The results presented in this report are based on regular large-scale surveys of seabird occurrence in the German North and Baltic Seas. These observations are based on standardised methods and provide data on spatio-temporal patterns and habitat use of seabirds in the ecosystems of the North Sea and Baltic Sea.

Assessments within the framework of Birds Directive and MSFD and the development of indicators for OSPAR and HELCOM are based on these data. The data and findings furthermore contribute to marine spatial planning and the assessment of anthropogenic activities.

Survey Overview

North Sea A five-day aerial survey of the entire German Bight was planned for winter. For logistical reasons, (weather, plane availability) only three days were implemented. The five-day aerial spring survey of the German Bight which focused on the SPA Eastern German Bight was shortened by one day due to logistics. The five-day aerial survey of the German Bight during breeding season was implemented in full. The three cancelled aerial survey days were reallocated to a four-day joint survey of the Baltic Sea. The fifteen proposed ship-based survey days in the North Sea were implemented successfully (Table 1).

Baltic Sea A four-day aerial survey of the whole German Bight including the SPA Pommeranian Bight was conducted in winter as part of the international joint survey. As this survey had not been in the planning stage at the time of applying for funds, resources allotted to the North Sea were reallocated to this survey. A one-day aerial survey of the SPA Pomeranian Bay was conducted as planned in both

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summer and autumn. The number of ship-based surveys implemented in the eastern German Bight surpassed the number originally aimed for (Table 1).

Table 1: Survey plan and implemenentaton in 2016. P= plane; Sh= dhip; EGB = Eastern German Bight; PoBay = Pomeranian Bay; w= winter; sp= spring, su = summer; au = autumn.

Survey planned implemented w sp su au w sp su Au entire German North Sea (January) p 5 3 entire survey (spring) p 5 4 SPA EGB & environs (spring) p th Sea entire North Sea (breeding season) p 5 3 Nor PhoViComp-Amrum Bank p 1 1 ship-based survey North Sea: ship of opportunity sh 15 15

entire German Baltic Sea (January) p 4 SPA Pomeranian Bay sh 7 7 7 7 partial survey SPA PoBay summer p 2 2

Baltic Sea ship-based survey Baltic Sea: ship of opportunity sh 8 15

Survey Results The course of the transect, the most important findings, and special observations of each individual survey are described below. Given that the spatial distribution of survey efforts may differ considerably, any numbers and density values are comparable to a limited extent only.

North Sea

Aerial seabird survey in the German Bight in February Seabirds of the German Bight were recorded during three monitoring flights between 26th and 29th February. We also present data from a survey flight monitoring the west coast of Schleswig-Holstein, funded by the Schleswig-Holstein Agency for Coastal Defence, National Park and Marine Conservation (LKN - Landesbetrieb für Küstenschutz, Nationalpark und Meeresschutz Schleswig- Holstein) (Figure 1). These data are included in the joint survey and are therefore presented together. Common scoters were the most abundant species with almost 35,000 individuals recorded and an average density of 18.85 individuals per km² (Table 2). The main distribution range of common scoters was southwest of Eiderstedt, west of the North Frisian Islands and north of the East Frisian Islands (Figure 2). Common eiders were abundant and predominantly observed near the coast. In addition, great numbers of seagulls as well as northern fulmars and auks were recorded. Three little auks, seven Atlantic puffins, a basking shark in the northwestern part of the EEZ and an unidentified shark west of Sylt are worthy of note (Table 2).

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Figure 1: Transect course of the aerial seabird survey in the German Bight in February 2016.

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Figure 2: Distribution of common scoters in the German Bight in February 2016.

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Table 2: Abundance and average density of species recorded in the transect during the aerial surveys of the German Bight in February 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 102 0.055 black-throated diver Gavia arctica 4 0.002 unidentified diver Gavia spec. 80 0.043 great crested grebe Podiceps cristatus 1 0.001 northern fulmar Fulmarus glacialis 198 0.106 northern gannet Morus bassanus 38 0.020 great cormorant Phalacrocorax carbo 1 0.001 greylag goose Anser anser 6 0.003 common shelduck Tadorna tadorna 2 0.001 common eider Somateria mollissima 4,414 2.367 common scoter Melanitta nigra 34,440 18.465 velvet scoter Melanitta fusca 6 0.003 unidentified duck 4 0.002 oystercatcher Haematopus ostralegus 111 0.060 unidentified sandpiper Calidris spec. 5 0.003 undetermined wader Limicolae 96 0.051 little gull Hydrocoloeus minutus 65 0.035 black-headed gull Chroicocephalus ridibundus 63 0.034 common gull Larus canus 402 0.216 unidentified small gull 12 0.006 lesser black-backed gull Larus fuscus 58 0.031 herring gull Larus argentatus 480 0.257 great black-backed gull Larus marinus 16 0.009 common / herring gull Larus canus / Larus argentatus 114 0.061 unidentified large gull 235 0.126 great / lesser black-backed gull Larus marinus / Larus fuscus 3 0.002 black-legged kittiwake Rissa tridactyla 163 0.087 unidentified gull 1,187 0.636 common guillemot Uria aalge 280 0.150 razorbill Alca torda 76 0.041 common guillemot / razorbill Uria aalge / Alca torda 213 0.114 little auk Alle alle 3 0.002 Atlantic puffin Fratercula arctica 7 0.004 unidentified bird 4 0.002 unidentified marine mammal 3 0.002 harbour porpoise Phocoena phocoena 54 0.029 grey / harbour seal 5 0.003 harbour seal Phoca vitulina 150 0.080 unidentified shark 1 0.001 basking shark Cetorhinus maximus 1 0.001

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Aerial seabird survey in the SPA Eastern German Bight in March An aerial survey of the SPA Eastern German Bight was implemented on 31st March (Figure 3). In terms of numbers, the scene was dominated by a variety of gull species (particularly common gulls, herring gulls, and lesser black-backed gulls). In addition, a number of divers and auks were observed (Table 3).The main distribution of divers was west of the SPA Eastern German Bight. However, numerous divers were observed in the SPA as well (Figure 4).

Figure 3: Transect course of the aerial seabird survey in the SPA Eastern German Bight in March 2016.

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Figure 4: Distribution of divers in the SPA Eastern German Bight in March 2016.

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Table 3: Abundance and average density of species recorded in the transect during the aerial surveys of the SPA Eastern German Bight in March 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 97 0.190 black-throated diver Gavia arctica 3 0.006 unidentified diver Gavia spec. 86 0.168 nortern fulmar Fulmarus glacialis 7 0.014 northern gannet Morus bassanus 27 0.053 common eider Somateria mollissima 27 0.053 common scoter Melanitta nigra 9 0.018 little gull Hydrocoloeus minutus 21 0.041 black-headed gull Chroicocephalus ridibundus 17 0.033 common gull Larus canus 952 1.865 unidentified small gull 247 0.484 lesser black-backed gull Larus fuscus 151 0.296 herring gull Larus argentatus 268 0.525 great black-backed gull Larus marinus 1 0.002 common gull / herring gull Larus canus / Larus argentatus 3 0.006 unidentified large gull 92 0.180 black-legged kittiwake Rissa tridactyla 19 0.037 unidentified gull 68 0.133 sandwich tern Sterna sandvicensis 5 0.010 common / Arctic tern Sterna hirundo / Sterna paradisaea 1 0.002 common guillemot Uria aalge 38 0.074 common guillemot / razorbill Uria aalge / Alca torda 24 0.047 undetermined songbird 4 0.008 harbour porpoise Phocoena phocoena 12 0.024 grey / harbour seal 4 0.008 grey seal Halichoerus grypus 1 0.002 harbour seal Phoca vitulina 3 0.006

Aerial seabird survey of the inner German Bight in May The inner German Bight was covered by two aerial sureys on 1st and 4th May (Figure 5). In terms of numbers, divers (mainly red-throated divers), lesser black-backed gulls, herring gulls, little gulls, black-legged kittiwakes, terns, and auks dominated the scene. Three Arctic skuas, an unidentified skua, two bottlenose dolphins, and several harbour porpoises were observed as well (Table 4). Divers were mainly found in the northern part of the German Bight (particularly the SPA Eastern German Bight and west of it) at this late stage of the spring migration (Figure 6).

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Figure 5: Transect course of the aerial seabird survey in the inner German Bight in May 2016.

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Figure 6: Distribution of divers in the inner German Bight in May 2016.

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Table 4: Abundance and average density of species recorded in the transect during the aerial surveys in the inner German Bight in May 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 385 0.233 black-throated diver Gavia arctica 2 0.001 unidentified diver Gavia spec. 146 0.088 northern fulmar Fulmarus glacialis 36 0.022 northern gannet Morus bassanus 76 0.046 brent goose Branta bernicla 2 0.001 common eider Somateria mollissima 7 0.004 common scoter Melanitta nigra 72 0.044 Arctic skua Stercorarius parasiticus 3 0.002 unidentified skua Stercorarius spec. 1 0.001 little gull Hydrocoloeus minutus 252 0.152 black-headed gull Chroicocephalus ridibundus 19 0.011 common gull Larus canus 17 0.010 unbestimmte Kleinmöwe 88 0.053 lesser black-backed gull Larus fuscus 1,215 0.735 herring gull Larus argentatus 314 0.190 great black-backed gull Larus marinus 2 0.001 unidentified large gull 50 0.030 black-legged kittiwake Rissa tridactyla 169 0.102 unidentified gull 6 0.004 sandwich tern Sterna sandvicensis 147 0.089 common tern Sterna hirundo 2 0.001 Arctic tern Sterna paradisaea 4 0.002 common / Arctic tern Sterna hirundo / Sterna paradisaea 445 0.269 unidentified Sterna-tern Sterna spec. 50 0.030 unidentified tern Sternidae 63 0.038 common guillemot Uria aalge 403 0.244 common guillemot / razorbill Uria aalge / Alca torda 67 0.041 unidentified piper Anthus spec. 3 0.002 unidentified bird 6 0.004 unidentified songbird 4 0.002 unidentified marine mammal 8 0.005 bottlenose dolphin Tursiops truncatus 2 0.001 harbour porpoise Phocoena phocoena 379 0.229 grey / harbour seal 17 0.010 grey seal Halichoerus grypus 6 0.004 harbour seal Phoca vitulina 48 0.029

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Ship-based seabird survey in the German Bight in June A ship-based seabird survey in the German Bight was carried out aboard ship of opportunity “Heincke” between 22nd of June and 1st of July, with surveyors joining a research team from the Institute of Hydrobiology and Fisheries Science of the University of Hamburg (Figure 7). The survey focused on fish distribution both inside and outside of offshore wind parks but provided an opportunity to monitor seabirds at the same time. Lesser black-backed gulls, common guillemots, northern gannets, northern fulmars, und black-legged kittiwakes dominated the scene (Table 5). Northern fulmars were particularly abundant in the western and northwestern part of the study site (Figure 8). A Manx shearwater was spotted among the more common seabirds.

Figure 7: Transect course of the ship-based seabird survey in the German Bight in June 2016.

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Figure 8: Distribution of northern fulmars in the German Bight in June 2016.

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Table 5: Abundance and average density of species recorded in the transect during the aerial surveys in the inner German Bight in June 2016.

species scientific name count density [ind. /km²] northern fulmar Fulmarus glacialis 16 0.046 Manx shearwater Puffinus puffinus 1 0.003 northern gannet Morus bassanus 23 0.066 black-headed gull Chroicocephalus ridibundus 2 0.006 lesser black-backed gull Larus fuscus 180 0.514 great black-backed gull Larus marinus 1 0.003 black-legged kittiwake Rissa tridactyla 12 0.034 sandwich tern Sterna sandvicensis 5 0.014 common guillemot Uria aalge 46 0.131 swift Apus apus 1 0.003

Aerial seabird survey in the German Bight in June Aerial seabird surveys in the German Bight were carried out on 6th June, 7th June and 11th June (Figure 9). Common pelagic species like black-legged kittiwakes, lesser black-backed gulls, northern gannets, and northern fulmars dominated the scene (Table 6). Two minke whales, several harbour porpoises, a basking shark, and an unidentified shark were observed. Black-legged kittiwakes frequented the western and northwestern part of the study area (Figure 10).

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Figure 9: Transect course of the aerial seabird survey in the German Bight in June 2016.

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Figure 10: Distribution of black-legged kittiwakes in the German Bight in June 2016.

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Table 6: Abundance and average density of species recorded in the transect during the aerial surveys in the German Bight in June 2016.

species scientific name count density [ind./km²] northern fulmar Fulmarus glacialis 104 0.056 northern gannet Morus bassanus 166 0.089 cormorant Phalacrocorax carbo 1 0.001 unidentified goose Anser / Branta spec. 2 0.001 common gull Larus canus 2 0.001 unidentified small gull 1 0.001 lesser black-backed gull Larus fuscus 277 0.149 herring gull Larus argentatus 12 0.006 great black-backed gull Larus marinus 2 0.001 unidentified large gull 4 0.002 black-legged kittiwake Rissa tridactyla 295 0.159 unidentified gull 3 0.002 sandwich tern Sterna sandvicensis 15 0.008 common / Arctic tern Sterna hirundo / Sterna paradisaea 4 0.002 unidentified Sterna-tern Sterna spec. 2 0.001 common guillemot Uria aalge 53 0.029 common guillemot / razorbill Uria aalge / Alca torda 17 0.009 razorbill Alca torda 2 0.001 unidentified bird 2 0.001 unidentified marine mammal 3 0.002 minke whale Balaenoptera acutorostrata 2 0.001 harbour porpoise Phocoena phocoena 144 0.078 grey/ harbour seal 5 0.003 harbour seal Phoca vitulina 14 0.008 unidentified shark 1 0.001 basking shark Cetorhinus maximus 1 0.001

Ship-based seabird survey in the German Bight in July A ship-based seabird survey was conducted aboard ship of opportunity „Heincke“ in the German Bight between 8th and 15th July, with a focus on Dogger Bank. The survey team joined a benthos survey of the AWI (Alfred-Wegener Institute), part of a monitoring survey of the BfN (German Federal Agency for Nature Conservation) (Figure 11). Common guillemots were the most abundant species with 290 observed individuals and an average density of 1.7 ind./km². Particularly noteworthy are five white-beaked dolphins, two minke whales, and an unidentified large whale which were observed in the transect (Table 7). Two additional minke whales and a Manx shearwater were seen outside of the transect. Common guillemots were particularly abundant around Helgoland and in the shallow water of Dogger Bank (Figure 12).

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Figure 11: Transect course of the ship-based seabird survey in the German Bight in July 2016.

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Figure 12: Distribution of common guillemots in the German Bight in July 2016.

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Table 7: Abundance and average density of species recorded in the transect during the ship-based surveys in the German Bight in July 2016.

species scientific name count density [ind. /km²] northern fulmar Fulmarus glacialis 7 0.042 northern gannet Morus bassanus 15 0.090 cormorant Phalacrocorax carbo 3 0.018 common eider Somateria mollissima 1 0.006 black-headed gull Chroicocephalus ridibundus 24 0.143 common gull Larus canus 4 0.024 lesser black-backed gull Larus fuscus 48 0.287 herring gull Larus argentatus 3 0.018 great black-backed gull Larus marinus 2 0.012 black-legged kittiwake Rissa tridactyla 11 0.066 common tern Sterna hirundo 11 0.066 Arctic tern Sterna paradisaea 3 0.018 common / Arctic tern Sterna hirundo / Sterna paradisaea 6 0.036 common guillemot Uria aalge 290 1.733 razorbill Alca torda 4 0.024 unidentified marine mammal 1 0.006 unidentified large whale 1 0.006 minke whale Balaenoptera acutorostrata 2 0.012 white-beaked dolphin Lagenorhynchus albirostris 5 0.030 harbour porpoise Phocoena phocoena 3 0.018 harbour seal Phoca vitulina 2 0.012

Aerial seabird survey in the inner German Bight in late summer An aerial seabird survey took place in the inner German Bight in late summer, 26th July and 16th August (Figure 13). One of the surveys was implemented simultaneously with a digital comparison survey (BfN project PhoViComp). In terms of numbers, the scene was dominated by common scoters, lesser black-backed gulls, common guillemots, terns, and black-legged kittiwakes (Table 8). The black- legged kittiwakes were concentrated to the west of their breeding colony on Helgoland, along the late-Pleistocene paleo Elbe River valley, auf (Figure 14). Of note is the sighting of a bottlenose dolphin.

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Figure 13: Transect course of the aerial seabird survey in the inner German Bight in late summer 2016.

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Figure 14: Distribution of black-legged kittiwakes in the inner German Bight in late summer 2016.

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Table 8: Abundance and average density of species recorded in the transect during the aerial seabird surveys in the inner German Bight in late summer 2016.

species scientific name count density [ind. /km²] unidentified diver Gavia spec. 1 0.001 northern fulmar Fulmarus glacialis 1 0.001 northern gannet Morus bassanus 69 0.061 common scoter Melanitta nigra 1,043 0.916 oystercatcher Haematopus ostralegus 1 0.001 unidentified wader Limicolae 2 0.002 little gull Hydrocoloeus minutus 20 0.018 black-headed gull Chroicocephalus ridibundus 25 0.022 common gull Larus canus 65 0.057 unidentified small gull 5 0.004 lesser black-backed gull Larus fuscus 612 0.538 herring gull Larus argentatus 52 0.046 great black-backed gull Larus marinus 1 0.001 unidentified large gull 2 0.002 black-legged kittiwake Rissa tridactyla 265 0.233 unidentified gull 2 0.002 sandwich tern Sterna sandvicensis 59 0.052 common tern Sterna hirundo 27 0.024 Arctic tern Sterna paradisaea 20 0.018 common / Arctic tern Sterna hirundo / Sterna paradisaea 506 0.444 unidentified Sterna-tern Sterna spec. 1 0.001 black tern Chlidonias niger 6 0.005 unidentified tern Sternidae 1 0.001 common guillemot Uria aalge 601 0.528 common guillemot / razorbill Uria aalge / Alca torda 5 0.004 razorbill Alca torda 3 0.003 unidentified marine mammal 1 0.001 bottlenose dolphin Tursiops truncatus 1 0.001 harbour porpoise Phocoena phocoena 22 0.019 grey / harbour seal 9 0.008 grey seal Halichoerus grypus 3 0.003 harbour seal Phoca vitulina 21 0.018

Aerial seabird survey in the German Bight in December Two aerial surveys took place in the German Bight, on 4th and 5th December (Figure 15). The bulk of observed birds consisted of common gulls, common scoters, black-legged kittiwakes and guillemots. Two little auks and two unidentified dolphins were further observed (Table 9). The main distribution range of divers was around Helgoland and to the north of the East Frisian Islands. They were completely absent in the northwestern part of the German EEZ (Figure 16). Atlantic puffins were unusually abundant with more than 30 individuals, mostly observed in the northwestern part of the German EEZ (Figure 17).

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Figure 15: Transect course of the aerial seabird survey in the German Bight in December 2016.

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Figure 16: Distribution of divers in the German Bight in December 2016.

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Figure 17: Distribution of Atlantic puffins in the German Bight in December 2016.

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Table 9: Abundance and average density of species recorded in the transect during the aerial seabird surveys in the German Bight in December 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 23 0.028 black-throated diver Gavia arctica 1 0.001 unidentified diver Gavia spec. 46 0.057 northern fulmar Fulmarus glacialis 24 0.030 northern gannet Morus bassanus 43 0.053 cormorant Phalacrocorax carbo 1 0.001 common scoter Melanitta nigra 597 0.737 unidentified duck 12 0.015 little gull Hydrocoloeus minutus 15 0.019 Sabine’s gull Xema sabini 1 0.001 black-headed gull Chroicocephalus ridibundus 5 0.006 common gull Larus canus 771 0.952 unidentified small gull 17 0.021 lesser black-backed gull Larus fuscus 6 0.007 herring gull Larus argentatus 47 0.058 herring /Caspian /yellow-legged Larus argentatus / L. gull cachinnans / L. michahellis 1 0.001 great black-backed gull Larus marinus 8 0.010 unidentified large gull 3 0.004 black-legged kittiwake Rissa tridactyla 254 0.314 unidentified gull 25 0.031 common guillemot Uria aalge 232 0.287 common guillemot / razorbill Uria aalge / Alca torda 162 0.200 razorbill Alca torda 18 0.022 little auk Alle alle 2 0.002 Atlantic puffin Fratercula arctica 32 0.040 unidentified auk 61 0.075 unidentified bird 5 0.006 unidentified marine mammal 2 0.002 unidentified dolphin 2 0.002 harbour porpoise Phocoena phocoena 10 0.012 grey / harbour seal 2 0.002 harbour seal Phoca vitulina 6 0.007

Baltic Sea

Ship-based seabird survey in the Pomeranian Bay in January A ship-based seabird survey in the Pomeranian Bay was carried out as charter survey with the „Skoven“ between 12th and 18th January (Figure 18). Seaducks, divers, and sawbills made up the bulk of observed birds. In addition, a number of divers, grebes, and cormorants were sighted. Particularly noteworthy are 53 Slavonian grebes and 10 black guillemots. Only a small number of auks were

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recorded (Table 10). Long-tailed ducks were observed at high densities on the Odra Bank, at the Adler Ground, the Bay of and along the coast of (Figure 19).

Figure 18: Transect course of the ship-based seabird survey in the Pomeranian Bay in January 2016.

Figure 19: Distribution of long-tailed ducks in the Pomeranian Bay in January 2016.

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Table 10: Abundance and average density of species recorded in the transect during the ship-based seabird surveys in the Pomeranian Bay in January 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 17 0.059 black-throated diver Gavia arctica 9 0.031 unidentified diver Gavia spec. 19 0.066 great crested grebe Podiceps cristatus 482 1.683 red-necked grebe Podiceps grisegena 12 0.042 Slavonian grebe Podiceps auritus 53 0.185 cormorant Phalacrocorax carbo 273 0.953 mute swan Cygnus olor 4 0.014 Eurasian wigeon Anas penelope 2 0.007 mallard Anas platyrhynchos 1 0.003 tufted duck Aythya fuligula 1,192 4.162 tufted duck / greater scaup Aythya fuligula / Aythya marila 1 0.003 greater scaup Aythya marila 1,183 4.131 long-tailed duck Clangula hyemalis 8,921 31.149 common scoter Melanitta nigra 741 2.587 velvet scoter Melanitta fusca 1,674 5.845 goldeneye Bucephala clangula 1,054 3.680 smew Mergus albellus 44 0.154 red-breasted merganser Mergus serrator 2,297 8.020 goosander Mergus merganser 730 2.549 Eurasian coot Fulica atra 6 0.021 black-headed gull Chroicocephalus ridibundus 1 0.003 common gull Larus canus 37 0.129 herring gull Larus argentatus 140 0.489 great black-backed gull Larus marinus 20 0.070 common guillemot Uria aalge 38 0.133 common guillemot / razorbill Uria aalge / Alca torda 13 0.045 razorbill Alca torda 18 0.063 black guillemot Cepphus grylle 10 0.035 grey seal Halichoerus grypus 9 0.031

Ship-based seabird survey in the western German Baltic Sea in February Ship-based seabird surveys in the western German Baltic Sea were conducted aboard ship of opportunity „Haithabu“ between 15th and 18th February and between 22nd and 24th February (Figure 20). In addition to several seaducks, a number of herring gulls, great crested grebes, and cormorants were observed. Divers and auks only occurred in small numbers. The sightings of two northern gannets to the west of and off Travemünde (one of which was spotted outside of the transect) and of two bottlenose dolphins in the Flensburg Fjord (both outside of the transect) are noteworthy (Table 11). Common eiders were observed at high densities in the shallow waters of the Flensburg, Eckernförde, and Kiel Fjord as well as around Fehmarn and in the Bay of Neustadt (Figure 21). 29

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Figure 20: Transect course of ship-based seabird surveys in the western German Baltic Sea in February 2016.

Figure 21: Distribution of common eiders in the western German Baltic Sea in February 2016.

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Table 11: Abundance and average density of species recorded in the transect during the ship-based seabird surveys in the western German Baltic Sea in February 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 4 0.027 little grebe Tachybaptus ruficollis 20 0.134 great crested grebe Podiceps cristatus 266 1.786 red-necked grebe Podiceps grisegena 6 0.040 Slavonian grebe Podiceps auritus 11 0.074 unidentified grebe Podicipedidae 5 0.034 northern gannet Morus bassanus 1 0.007 cormorant Phalacrocorax carbo 237 1.591 mute swan Cygnus olor 3 0.020 whooper swan Cygnus cygnus 1 0.007 greylag goose Anser anser 136 0.913 common shelduck Tadorna tadorna 2 0.013 mallard Anas platyrhynchos 32 0.215 tufted duck Aythya fuligula 153 1.027 common eider Somateria mollissima 8,764 58.831 long-tailed duck Clangula hyemalis 1,105 7.418 common scoter Melanitta nigra 965 6.478 velvet scoter Melanitta fusca 130 0.873 goldeneye Bucephala clangula 266 1.786 red-breasted merganser Mergus serrator 99 0.665 goosander Mergus merganser 65 0.436 Eurasian coot Fulica atra 57 0.383 little gull Hydrocoloeus minutus 1 0.007 black-headed gull Chroicocephalus ridibundus 5 0.034 common gull Larus canus 71 0.477 herring gull Larus argentatus 317 2.128 great black-backed gull Larus marinus 40 0.269 common guillemot Uria aalge 12 0.081 razorbill Alca torda 32 0.215 common guillemot / razorbill Uria aalge / Alca torda 9 0.060 unidentified auk 4 0.027 skylark Alauda arvensis 2 0.013 hooded crow Corvus corone corone 2 0.013 harbour porpoise Phocoena phocoena 2 0.013

Aerial seabird survey in the German Baltic Sea in February An aerial survey of the entire German Baltic Sea was carried out on 13th, 16th, and 19th February (Figure 22). In addition to many seaducks, a large number of divers, cormorants, and seagulls were observed (Table 12). A white-billed diver was sighted north of Zingst. Long-tailed ducks were especially frequent in the Pomeranian Bay, the , and to the north of Darß/Zingst/Fischland but were also seen in large numbers in the shallow waters of the western German Baltic Sea (Figure 23). 31

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Figure 22: Transect course of the aerial seabird surveys in the German Baltic Sea in February 2016.

Figure 23: Distribution of long-tailed ducks in the German Baltic Sea in February 2016.

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Table 12: Abundance and average density of species recorded in the transect during the aerial surveys in the German Baltic Sea in February 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 118 0.066 black-throated diver Gavia arctica 13 0.007 white-billed diver Gavia adamsii 1 0.001 unidentified diver Gavia spec. 522 0.293 great crested grebe Podiceps cristatus 12 0.007 Slavonian grebe Podiceps auritus 2 0.001 unidentified grebe Podicipedidae 7 0.004 cormorant Phalacrocorax carbo 200 0.112 mute swan Cygnus olor 15 0.008 unidentified swan Cygnus spec. 3 0.002 unidentified goose Anser / Branta spec. 2 0.001 Canada goose Branta canadensis 15 0.008 mallard Anas platyrhynchos 12 0.007 pochard Aythya ferina 2 0.001 greater scaup Aythya marila 60 0.034 unidentified diving duck Aythya spec. 3 0.002 common eider Somateria mollissima 11,916 6.689 long-tailed duck Clangula hyemalis 11,494 6.452 common scoter Melanitta nigra 8,777 4.927 common scoter / celvet scoter Melanitta nigra / Melanitta fusca 760 0.427 velvet scoter Melanitta fusca 1,730 0.971 goldeneye Bucephala clangula 143 0.080 red-breasted merganser Mergus serrator 13 0.007 goosander Mergus merganser 4 0.002 unidentified duck 14 0.008 little gull Hydrocoloeus minutus 6 0.003 black-headed gull Chroicocephalus ridibundus 12 0.007 common gull Larus canus 153 0.086 unidentified small gull 8 0.004 herring gull Larus argentatus 1,069 0.600 great black-backed gull Larus marinus 136 0.076 unidentified large gull 19 0.011 unidentified gull 133 0.075 common guillemot Uria aalge 68 0.038 common guillemot / razorbill Uria aalge / Alca torda 179 0.100 razorbill Alca torda 27 0.015 black guillemot Cepphus grylle 4 0.002 unidentified thrush Turdus spec. 1 0.001 unidentified bird 50 0.028 unidentified songbird 12 0.007 harbour porpoise Phocoena phocoena 6 0.003 grey / harbour seal 1 0.001 grey seal Halichoerus grypus 2 0.001 33

Seabird Monitoring 2016

Ship-based seabird survey in the eastern German Bight in March A ship-based seabird survey of the eastern German Bight was carried out aboard HZG research vessel „Ludwig Prandtl“ between 7th and 14th March (Figure 24). Large numbers of seaducks dominated the scene. Further noteworthy are the number of Slavonian grebes and black guillemots (Table 13). The distribution of long-tailed ducks tallies with observations during the previous survey of the entire German Bight (Figure 25).

Figure 24: Transect course of ship-based seabird surveys in the eastern German Bight in March 2016.

Figure 25: Distribution of long-tailed ducks in the eastern German Baltic Sea in March 2016.

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Seabird Monitoring 2016

Table 13: Abundance and average density of species recorded in the transect during the ship-based surveys in the eastern German Baltic Sea in March 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 42 0.112 black-throated diver Gavia arctica 16 0.042 unidentified diver Gavia spec. 85 0.226 great crested grebe Podiceps cristatus 131 0.348 red-necked grebe Podiceps grisegena 8 0.021 Slavonian grebe Podiceps auritus 101 0.268 Slavonian / black-necked grebe Podiceps auritus / P. nigricollis 12 0.032 unidentified grebe Podicipedidae 26 0.069 northern gannet Morus bassanus 1 0.003 cormorant Phalacrocorax carbo 484 1.285 grey heron Ardea cinerea 1 0.003 mute swan Cygnus olor 158 0.420 whooper swan Cygnus cygnus 1 0.003 brent goose Branta bernicla 3 0.008 common shelduck Tadorna tadorna 35 0.093 Eurasian wigeon Anas penelope 678 1.800 mallard Anas platyrhynchos 168 0.446 northern pintail Anas acuta 5 0.013 tufted duck Aythya fuligula 2 0.005 greater scaup Aythya marila 3,353 8.904 common eider Somateria mollissima 2,534 6.729 long-tailed duck Clangula hyemalis 15,197 40.355 common scoter Melanitta nigra 27,986 74.316 velvet scoter Melanitta fusca 5,004 13.288 goldeneye Bucephala clangula 475 1.261 smew Mergus albellus 5 0.013 red-breasted merganser Mergus serrator 485 1.288 goosander Mergus merganser 193 0.513 Eurasian coot Fulica atra 57 0.151 common crane Grus grus 3 0.008 black-headed gull Chroicocephalus ridibundus 135 0.358 common gull Larus canus 18 0.048 herring gull Larus argentatus 508 1.349 great black-backed gull Larus marinus 72 0.191 unidentified Larus-gull Larus spec. 1 0.003 common guillemot Uria aalge 42 0.112 razorbill Alca torda 51 0.135 common guillemot / razorbill Uria aalge / Alca torda 46 0.122 black guillemot Cepphus grylle 12 0.032 skylark Alauda arvensis 8 0.021 hooded crow Corvus corone cornix 1 0.003 grey seal Halichoerus grypus 2 0.005 35

Seabird Monitoring 2016

Ship-based seabird survey in the Pomeranian Bay and in the Bay of Greifswald in August A ship-based seabird survey in the Pomeranian Bay and in the Bay of Greifswald was carried out aboard HZG research vessel „Ludwig Prandtl“ between 20th and 26th August (Figure 26). The survey recorded moulting common and velvet scoters at the Odra Bank. The scene was dominated by common scoters (Table 14). Due to increased disturbance vulnerability during the moult, a certain number of common and velvet scoters dived at great distance to the ship and could not be identified down to species level. Combining the data with those collected during an aerial survey on 28th August allows us to compare methodologies of ship-based and aerial monitoring of moulting common and velvet scoters. The distribution of common scoters was largely confined to the Odra Bank (Figure 27). Of note are a white-billed diver at the Odra Bank as well as large numbers of black and little terns which were predominantly observed in the Bay of Greifswald (Table 14).

Figure 26: Transect course of the ship-based seabird surveys in the Pomeranian Bay and in the Bay of Greifswald in August 2016.

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Seabird Monitoring 2016

Figure 27: Distribution of common scoters in the Pomeranian Bay and in the Bay of Greifswald in August 2016.

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Seabird Monitoring 2016

Table 14: Abundance and average density of species recorded in the transect during the ship-based surveys in the Pomeranian Bay and the Bay of Greifswald in August 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 1 0.003 black-throated diver Gavia arctica 7 0.020 white-billed diver Gavia adamsii 1 0.003 great crested grebe Podiceps cristatus 2 0.006 red-necked grebe Podiceps grisegena 7 0.020 Slavonian grebe Podiceps auritus 1 0.003 unidentified grebe Podicipedidae 2 0.006 cormorant Phalacrocorax carbo 797 2.258 mute swan Cygnus olor 7 0.020 Canada goose Branta canadensis 13 0.037 Eurasian teal Anas crecca 20 0.057 mallard Anas platyrhynchos 3 0.008 common scoter Melanitta nigra 3,077 8.717 common scoter / velvet scoter Melanitta nigra / Melanitta fusca 532 1.507 velvet scoter Melanitta fusca 43 0.122 knot Calidris canutus 1 0.003 little gull Hydrocoloeus minutus 10 0.028 black-headed gull Chroicocephalus ridibundus 92 0.261 common gull Larus canus 104 0.295 lesser black-backed gull Larus fuscus 1 0.003 herring gull Larus argentatus 185 0.524 Caspian gull Larus cachinnans 2 0.006 great black-backed gull Larus marinus 17 0.048 sandwich tern Sterna sandvicensis 4 0.011 common tern Sterna hirundo 7 0.020 little tern Sterna albifrons 26 0.074 black tern Chlidonias niger 29 0.082 common guillemot Uria aalge 18 0.051 swallow Hirundo rustica 9 0.025 unidentified songbird 4 0.011 harbour porpoise Phocoena phocoena 1 0.003

Aerial seabird survey in the Pomeranian Bay in August An aerial seabird survey in the Pomeranian Bay and the Bay of Greifswald was carried out on 27th and 31st August (Figure 28). Moulting common scoters are the only birds expected to be observed in large numbers at this time of the year. Compared to the ship-based survey (see above), only small numbers of seaducks were observed in this survey. We suspect that this observation is due to early diving of common and velvet scoters caused by disturbance vulnerability during the moult. Mute swans and dabbling ducks were essentially confined to the Bay of Greifswald. In addition to a number of cormorants, numerous little gulls were recorded. Sightings of an Arctic skua, six great egrets, and 250 avocets were among the most noteworthy observations (Table 15). Most little gulls were observed near Usedom (Figure 29).

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Seabird Monitoring 2016

Figure 28: Transect course of the aerial seabird surveys in the Pomeranian Bay in August 2016.

Figure 29: Distribution of little gulls in the Pomeranian Bay in August 2016.

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Seabird Monitoring 2016

Table 15: Abundance and average density of species recorded in the transect during the aerial surveys in the Pomeranian Bay in August 2016.

species scientific name count density [ind. /km²] red-throated diver Gavia stellata 7 0.008 black-throated diver Gavia arctica 1 0.001 unidentified diver Gavia spec. 14 0.017 great crested grebe Podiceps cristatus 4 0.005 red-necked grebe Podiceps grisegena 2 0.002 unidentified grebe Podicipedidae 2 0.002 cormorant Phalacrocorax carbo 690 0.813 great egret Egretta alba 6 0.007 mute swan Cygnus olor 1,688 1.990 greylag goose Anser anser 53 0.062 mallard Anas platyrhynchos 3 0.004 unidentified dabbling duck Anas spec. 1,982 2.336 common eider Somateria mollissima 17 0.020 common scoter Melanitta nigra 308 0.363 velvet scoter Melanitta fusca 18 0.021 goldeneye Bucephala clangula 3 0.004 red-breasted merganser Mergus serrator 1 0.001 unidentified duck 80 0.094 avocet Recurvirostra avosetta 250 0.295 curlew Numenius arquata 30 0.035 unidentified wader Limicolae 10 0.012 Arctic skua Stercorarius parasiticus 1 0.001 little gull Hydrocoloeus minutus 290 0.342 black-headed gull Chroicocephalus ridibundus 57 0.067 common gull Larus canus 8 0.009 unidentified small gull 454 0.535 lesser black-backed gull Larus fuscus 5 0.006 herring gull Larus argentatus 103 0.121 great black-backed gull Larus marinus 21 0.025 unidentified large gull 70 0.083 unidentified gull 1 0.001 sandwich tern Sterna sandvicensis 14 0.017 tern / small gull 2 0.002 common guillemot Uria aalge 105 0.124 common guillemot / razorbill Uria aalge / Alca torda 9 0.011 barn swallow Hirundo rustica 1 0.001 unidentified bird 43 0.051 unidentified songbird 2 0.002 black swan Cygnus atratus 1 0.001 harbour porpoise Phocoena phocoena 1 0.001

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Seabird Monitoring 2016

Further Results Current results of the monitoring surveys including sighting maps and density maps of all common seabird species are accessible on the website of the German Federal Agency for Nature Conservation (Bundesamt für Naturschutz - BfN), under geo-information services. https://www.bfn.de/themen/meeresnaturschutz/marines-monitoring.html

Acknowledgements Volker Dierschke helped organise aerial surveys. Observers Manfred Bögershausen, Jonas Buddemeier, Volker Dierschke, Margus Ellermaa, Katharina Fließbach, Martin Gottschling, Franziska Güpner, Johanna Kottsieper, Hilger Lemke, Marco Maier, Esther Rickert, and Stefan Weiel significantly contributed to the success of the surveys. Margus Ellermaa analysed the sex ratio and the young bird percentage of seaducks for the ship-based survey of the Baltic Sea. HZG made research vessel "Ludwig Prandtl" available for the March cruise. AWI, HZG and LLUR allowed us to join expeditions with the "Heincke" and the "Haithabu". We would like to thank Volker Dzaak, Brigitte Ebbe, Jens Floeter, and Angela Trumpf for planning and conducting these expeditions. We would also like to express our gratitude to captain, crew and fellow passengers for the cooperation and a pleasant time on board. Further many thanks to all pilots for a pleasant work environment and safe transport during aerial surveys. Eugen Faber and Uwe Lange of Brockmann Consult provided valuable assistance with data management.

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