Seabird Monitoring in the German North Sea and Baltic Sea 2015 photo: Kai Borkenhagen Kai Borkenhagen1, Nils Guse1, Mirko Hauswirth2, 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, Vilm, D-18581 Putbus Seabird Monitoring 2015 Introduction Seabirds, as top predators, are an important component of marine ecosystems. Anthropogenic activities, such as fisheries, development of offshore wind energy, shipping, marine pollution, etc. exert increasing pressure on them. The monitoring of their occurrence and precise knowledge of their distribution patterns, population numbers, trends and habitat requirements are prerequisites for their effective protection and successful management of protected areas. The Birds Directive (BD) and the Marine Strategy Framework Directive (MSFD) of the European Union require Member States to submit regular reports, based on the data regularly collected. In addition, the data are used to develop indicators for assessing the environmental status within the framework of the regional sea conventions OSPAR and HELCOM, and the data and knowledge gained is incorporated into marine spatial planning and the assessment of anthropogenic activities. The marine biodiversity monitoring programme for vertebrates is financed by the German Federal Agency for Nature Conservation (Bundesamt für Naturschutz - BfN) and carried out by the FTZ in collaboration with the German Oceanographic Museum Stralsund (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) with funds from the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (Bundesministerium für Umwelt, Naturschutz und Nukleare Sicherheit - BMU). The results presented here are based on repeated large-scale surveys of seabirds in the German North and Baltic Seas. These surveys are carried out following internationally standardized methods, and provide data on spatio-temporal patterns and habitat use of seabirds in the ecosystems of the North Sea and Baltic Sea. Survey overview North Sea In winter, a three-day aerial survey of the inner German Bight was planned and completed successfully. For logistical reasons (weather, aircraft availability), two days of the three-day aerial survey of the inner German Bight scheduled for spring had to be cancelled. Instead, an additional survey in the north-western part of the German EEZ, and an aerial survey in parallel to a digital comparison survey were conducted. Eight of the planned 15 days of ship-based survey in the North Sea were implemented. The remaining effort was reallocated to a survey in the Baltic Sea (Table 1). 1 Seabird Monitoring 2015 Baltic Sea A three-day aerial survey of the entire German Baltic Sea had been scheduled for winter. For logistic reasons all flights had to be cancelled and were reallocated to surveys in spring, summer and autumn in the area of the SPA Bay of Pomerania. The ship-based surveys in the eastern German Baltic Sea over-fulfilled the original plan (Table 1). Table 1: Survey plan and implementation of the German seabird monitoring programme in 2015. p= plane; sh= ship; EGB= Eastern German Bight; PomBay= Bay of Pomerania; wi= winter; sp= spring, su= summer; au= autumn. planned implemented Survey wi sp su au wi sp su au SPA EGB and adjacent areas (winter) p 3 3 SPA EGB and adjacent areas (spring) p 3 1 EEZ around Helgoland (summer) p 1 2 th Sea th North-western part of EEZ p 1 Nor Ship-based survey North Sea: vessel of sh 15 8 opportunity Entire German Baltic Sea (winter) p 3 0 SPA Bay of Pomerania, ship-based (winter) sh 7 7 Entire German Baltic Sea (spring) p 3 4 SPA PomBay (summer) p 2 Baltic Sea Ship-based Survey Baltic Sea: vessel of sh 4 8 opportunity Survey results In this chapter the study area, the most important results, and special observations are presented for each survey. Since the surveys sometimes differ considerably in the spatial distribution of the survey effort, the numbers and density values given in the tables are comparable only to a limited extent. North Sea Aerial survey of the eastern part of the German Bight in winter On 22nd of January and 11th of February the eastern part of the German Bight was covered with two aerial surveys (Figure 1). Small gaps in survey coverage are due to military activities. With about 14 500 individuals and an average density of 11.7 Ind./km² the Common scoter was the most abundant species (Table 2). The occurrence of Common scoters was concentrated near Eiderstedt, west of the North Frisian Islands, on the Amrumbank and north of the East Frisian Islands (Figure 2). In addition to numerous Common eiders, which were mainly observed in coastal areas, many divers and typical pelagic species, such as Northern gannet, Northern fulmar, auks and Black-legged kittiwake, were registered in the survey area (Table 1). 2 Seabird Monitoring 2015 Figure 1: Survey transects of the aerial seabird survey in the eastern German Bight in winter 2015. 3 Seabird Monitoring 2015 Table 2: Number and average density of species registered inside transect during the aerial seabird survey in the eastern German Bight in winter 2015. species scientific name number density [Ind./km²] Red-throated diver Gavia stellata 57 0,045 Black-throated diver Gavia arctica 2 0,002 unidentified diver Gavia spec. 48 0,038 Northern fulmar Fulmarus glacialis 26 0,021 Northern gannet Sula bassana 6 0,005 Greylag goose Anser anser 2 0,002 Common eider Somateria mollissima 1 180 0,941 Common scoter Melanitta nigra 14 635 11,667 Velvet scoter Melanitta fusca 1 0,001 Oystercatcher Haematopus ostralegus 1 0,001 Little gull Hydrocoloeus minutus 99 0,079 Black-headed gull Chroicocephalus ridibundus 14 0,011 Common gull Larus canus 125 0,100 unidentified small gull 327 0,261 Lesser black-backed gull Larus fuscus 1 0,001 Herring gull Larus argentatus 552 0,440 Great black-backed gull Larus marinus 23 0,018 unidentified large gull 2 0,002 Black-legged kittiwake Rissa tridactyla 140 0,112 unidentified gull 75 0,060 Common guillemot Uria aalge 67 0,053 Razorbill Alca torda 15 0,012 Common guillemot / Uria aalge / Alca torda 114 0,091 Razorbill Harbour porpoise Phocoena phocoena 67 0,053 Grey seal Halichoerus grypus 2 0,002 Harbour seal Phoca vitulina 7 0,006 Grey seal / Harbour seal 3 0,002 4 Seabird Monitoring 2015 Figure 2: Distribution of Common scoters in the eastern German Bight in winter 2015. Aerial survey of the eastern German Bight in spring On 18th of April the inner German Bight in the area of the Elbe estuary was surveyed with an aerial survey (Figure 3). Common scoters and Lesser black-backed gulls were the most abundant species with more than 450 individuals each, while almost 200 divers and more than 100 Little gulls were detected (Table 3). Divers concentrated in the North and West of the area covered, whereas only a few divers were found in the Elbe estuary (Figure 4). 5 Seabird Monitoring 2015 Figure 3: Survey transects of the aerial seabird survey in the eastern German Bight in spring 2015. 6 Seabird Monitoring 2015 Table 3: Number and average density of species registered inside transect during the aerial seabird survey in the inner German Bight in spring 2015. species scientific name number density [Ind./km²] Red-throated diver Gavia stellata 131 0,104 Black-throated diver Gavia arctica 10 0,008 unidentified diver Gavia spec. 54 0,043 Northern gannet Sula bassana 26 0,021 Great cormorant Phalacrocorax carbo 5 0,004 Common eider Somateria mollissima 1 0,001 Common scoter Melanitta nigra 466 0,371 Velvet scoter Melanitta fusca 2 0,002 Red-breasted merganser Mergus serrator 5 0,004 Little gull Hydrocoloeus minutus 106 0,084 Black-headed gull Chroicocephalus ridibundus 17 0,014 Common gull Larus canus 132 0,105 unidentified small gull 16 0,013 Lesser black-backed gull Larus fuscus 465 0,371 Herring gull Larus argentatus 188 0,150 unidentified large gull 4 0,003 Black-legged kittiwake Rissa tridactyla 180 0,143 unidentified gull 19 0,015 Sandwich tern Sterna sandvicensis 39 0,031 Common / Arctic tern Sterna hirundo / Sterna paradisaea 12 0,010 Common guillemot Uria aalge 58 0,046 Razorbill Alca torda 1 0,001 Common guillemot / Razorbill Uria aalge / Alca torda 20 0,016 unidentified songbird 2 0,002 Harbour porpoise Phocoena phocoena 28 0,022 Grey seal Halichoerus grypus 2 0,002 Harbour seal Phoca vitulina 6 0,005 Grey seal / Harbour seal 2 0,002 7 Seabird Monitoring 2015 Figure 4: Distribution of divers Gavia spec. in the eastern German Bight in spring 2015. Aerial survey of the area around Helgoland and the north-western German EEZ in summer On 4th of June, 11th of June, and 11th of July the aerial seabird surveys for summer took place in the German North Sea (Figure 5). In addition to about 2 800 Common scoters, a large number of pelagic species, such as Black-legged kittiwakes, Northern gannets, auks and Northern fulmars, were recorded (Table 4). Next to a hotspot on the Dogger Bank, Black-legged kittiwakes were found throughout the entire area and were only absent in the easternmost part (Figure 6). In addition to seabirds, almost 250 harbour porpoises, one Common minke whale, seven unidentified dolphins and several seals were observed (Table 4). The aerial survey on 11th of July was implemented parallel to a digital comparison survey (HELBIRD project) north of Helgoland and achieved a small-scale picture of bird distribution around the offshore wind farms of the Helgoland cluster.