Georeferenced digital photography for an objective and reproducible quantification of staging sea birds [Georeferenzierte Digitalfotografie zur objektiven und reproduzierbaren Quantifizierung von Rastvögeln auf See]
Kulemeyer C.,Institute For Angewandte Okosystemforschune Ifao |
Schulz A.,Institute For Angewandte Okosystemforschune Ifao |
Weidauer A.,Institute For Angewandte Okosystemforschune Ifao |
Rohrbein V.,Institute For Angewandte Okosystemforschune Ifao |
And 4 more authors.
Vogelwarte | Year: 2011
An expansion of offshore wind energy production could lead to a significant loss of wintering and staging habitats for seabirds. To assess the impact of wind farms before, during and after their construction, the standard investigation concept of the Federal Maritime and Hydrographic Agency (BSH) currently recommends ship- and aircraft-based bird surveys. Observationbased aerial surveys, however, have methodological disadvantages: Low flight elevation (78 m), necessary for species recognition, and high flight speed in combination with large numbers of birds allow only rough population estimates. In addition, aircrafts flying at this elevation disturb resting birds, further obstructing their quantification. In this pilot study, we compared visually estimated seabird numbers collected during an aerial transect survey with numbers derived from digital aerial photographs of the same transects. The photographic survey was carried out shortly before the visual survey at a height of 200 m above sea level using a high-resolution digital camera (39 Mega pixels). 415 vertical photos corrected for geometry and scale were taken at regular intervals along defined transects. The results of this study suggest that the observational survey significantly underestimated the number of sea ducks. The difference between visual and photographic methods varied considerably among species: 85% (Common Eider, Somateria mollissima), 41% (Long-tailed Duck, Clangula hyemalis) and only 2% (Common Scoter, Melanitta nigra) of the photographically documented individuals were observed. The reasons for these quantitative differences are discussed. © DO-G, IfV, MPG 2011.