Seabird Monitoring in the German North Sea and Baltic Sea 2018
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Seabird Monitoring in the German North Sea and Baltic Sea 2018 Photo: Kai Borkenhagen Kai Borkenhagen, Nils Guse, Hanna Markones, Nele Markones, Henriette Schwemmer, Stefan Garthe Research and Technology Centre West Coast (FTZ), Kiel University, Hafentörn 1, D-25761 Büsum Seabird Monitoring 2018 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, and the data and knowledge gained are incorporated into marine spatial planning and the assessment of anthropogenic activities. 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 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), using funds of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU). 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 Two aerial survey days in the inner German Bight were successfully carried out, as planned, in winter. Only one of three proposed aerial survey days in the German Bight in spring could be implemented due to logistics (weather, aircraft availability). One day was reallocated to the north-western-most part of the German Exclusive Economic Zone (EEZ), one day was cancelled. In addition, observer- based aerial surveys were carried out simultaneously with two digital comparison surveys of the PhoViComp project in spring. The area around Helgoland was covered by a one-day aerial survey in summer, as scheduled. A number of the flight surveys were carried out simultaneously or near- simultaneously with digital surveys along the same transects. However, this report focusses on results of the observer-based surveys only, because the digital survey data were not available at the time of writing this report. Thirteen of fifteen proposed survey days on ships of opportunity were implemented successfully (Table 1). 1 Seabird Monitoring 2018 Baltic Sea Two days of a proposed three-day ship-based survey of the entire Baltic Sea in winter went ahead as scheduled, one day was cancelled for logistical reasons. Only one of two proposed aerial survey days in the Pomeranian Bay in summer could be implemented, the other one was cancelled due to logistics. Two aerial surveys scheduled alongside the digital comparison surveys of the PhoViComp project had to be cancelled, because weather conditions were unsuitable. A dedicated seven-day ship-based survey in the Pomeranian Bay in winter was carried out successfully aboard chartered vessel „Skoven“ in January. A seven-day ship-based survey in the Pomeranian Bay and west of Rügen in spring was successfully implemented aboard the „Ludwig Prandtl“ of the HZG (Helmholtz-Zentrum Geesthacht) in March. In addition, a seven-day ship-based survey in the Pomeranian Bay and west of Rügen aboard the „Ludwig Prandtl“ of the HZG in autumn was successfully carried out in November. Six of eight scheduled survey days on ships of opportunity were carried out aboard the „Haithabu“ in the western Baltic Sea in February (Table 1). Table 1: Survey design and implementation in 2018. p= plane; sh= ship; EGB = Eastern German Bight; PoBay = Pomeranian Bay; w = winter; sp= spring, s= summer; au= autumn. 2018 2018 survey w Sp s au w sp s au SPA EGB and environs winter p 2 2 SPA EGB and environs spring p 3 1 EEZ off Helgoland: summer p 1 1 North-western EEZ p 1 North Sea PhoViComp-Amrum Bank p 2 2 ship-based survey North Sea sh 15 13 entire German Baltic Sea January p 3 2 SPA Pomeranian Bay ship sh 7 7 7 7 7 partial survey SPA PoBay summer p 2 1 PhoViComp-PoBay 1 1 0 0 Baltic Sea ship-based survey Baltic Sea (ship of opportunity) sh 8 6 2 Seabird Monitoring 2018 Survey Results The course of the transect, the most important findings, and special observations of each individual survey are described below. Densities of all species observed within the transect are shown in the tables, disregarding distance correction. Given that the spatial distribution of survey efforts may differ considerably, any numbers and density values are comparable to a limited extent only. All distribution maps are based on distance-corrected numbers of birds. North Sea Aerial seabird survey in the inner German Bight in February Two aerial seabird surveys were carried out in the inner German Bight on 6th of February and 22nd of February (Figure 1). Data were collected using a newly launched joint transect design of digital and observer-based surveys. The transect design for the monitoring of seabirds and marine mammals was developed in close coordination between ITAW and FTZ. The surveys were carried out simultaneously or near-simultaneously with digital surveys on the same transects. The SPA Eastern German Bight could not be surveyed by observers due to logistics but was covered digitally. The digital survey data were not available at the time of writing this report. Auks and gulls made up the majority of sightings, in addition to common eiders and common scoters which were predominantly observed near the coast (Table 2). Black-legged kittiwakes were most frequent in the north-western part of the study site and were completely absent in areas near the coast (Figure 2). The greatest density of common guillemots and razorbills was observed north of the East Frisian Islands and along the late-Pleistocene paleo Elbe River valley (Figure 3). 94% of alcids identified to species-level were common guillemots. 3 Seabird Monitoring 2018 Figure 1: Transect course of the aerial seabird survey in the inner German Bight in February 2018. Data were collected using a newly launched joint transect design of digital and observer-based surveys of seabirds and marine mammals. 4 Seabird Monitoring 2018 Figure 2: Distribution of black-legged kittiwakes in the inner German Bight in February 2018. 5 Seabird Monitoring 2018 Figure 3: Distribution of common guillemots and razorbills in the inner German Bight in February 2018. The common guillemot made up 94% of all individuals identified to species level. 6 Seabird Monitoring 2018 Table 2: Abundance and average density of species recorded in the transect during the aerial surveys of the inner German Bight in February 2018. species scientific name count density [ind. /km²] red-throated diver Gavia stellata 37 0.043 black-throated diver Gavia arctica 3 0.003 unidentified diver Gavia spec. 66 0.077 northern fulmar Fulmarus glacialis 3 0.003 northern gannet Morus bassanus 15 0.017 greylag goose Anser anser 7 0.008 common eider Somateria mollissima 4,758 5.524 common scoter Melanitta nigra 448 0.520 oystercatcher Haematopus ostralegus 20 0.023 dunlin Calidris alpina 40 0.046 little gull Hydrocoloeus minutus 7 0.008 common gull Larus canus 99 0.115 unidentified small gull 2 0.002 lesser black-backed gull Larus fuscus 2 0.002 herring gull Larus argentatus 209 0.243 great black-backed gull Larus marinus 41 0.048 common / herring gull Larus canus / Larus argentatus 1 0.001 unidentified large gull 1 0.001 black-legged kittiwake Rissa tridactyla 197 0.229 unidentified gull 23 0.027 common guillemot Uria aalge 199 0.231 common guillemot / razorbill Uria aalge / Alca torda 184 0.214 razorbill Alca torda 13 0.015 unidentified bird 9 0.010 harbour porpoise Phocoena phocoena 32 0.037 grey seal / harbour seal 4 0.005 grey seal Halichoerus grypus 3 0.003 harbour seal Phoca vitulina 3 0.003 Aerial seabird survey in the German Bight in spring Parts of the German Bight were covered by aerial seabird surveys on 21st of April, 4th of May, 11th of May, and 15th of May (Figure 4). All surveys were conducted simultaneously with digital surveys. The two surveys north of Helgoland were carried out at the same time as digital comparison surveys of the PhoViComp project. This report only presents results of observer-based surveys. In terms of numbers, divers, northern gannets, seaducks, gulls, terns, and guillemots dominated the scene (Table 3). Red-throated divers were most frequent in the main density area to the northwest of Helgoland, while almost absent in the northwestern part of the EEZ (Exclusive Economic Zone) and at the mouth of the Elbe River (Figure 5). Of all gulls, the little gull was the most abundant species, They were even more common than the lesser black-backed gull, which is the typical „offshore gull“ of the German Bight between spring and autumn.