Status report of seabird surveys at Horns Rev, 2000-2001

The present report presents the results of three bird surveys conducted in the Horns Rev area during the second half of 2001. Due to poor weather conditions in December 2001, the last survey was, however, performed on 7 January 2002. The surveys are part of the base-line investigations of birds performed in relation to the proposed construction of an offshore wind farm at Horns Rev in the Danish part of the North Sea ca 14 km southwest of Blaevandshuk. The results of the surveys during August 2001 - January 2002 are presented together with the results obtained during the period August 2000 - April 2001, and are also compared to results obtained during the period August 1999 - April 2000. Based on the distribution of the most abundant bird species recorded during 16 aerial surveys performed during August 1999 - January 2002, there were no indications that the wind farm area was of any particular importance to the birds' exploitation of the Horns Rev area. Fish-eating species like divers, gannet, terns, auks and gulls generally showed scattered and variable distributions, mainly occurring in the areas north and south of Horns Rev, and with low numbers on the reef proper and within the planned wind farm area. The distribution of benthic foraging species, eider and common Scoter, showed that they mainly exploited the coastal parts of the area off Blaevandshuk and Skallingen, although common scoter was found in relatively high numbers on the southeast slopes of the Horns Rev and within the wind farm area in the April 2001 survey. Common scoters occurred in very high numbers in January 2002. This was probably related to increased immigration of birds from the inner Danish waters during a cold period in late December 2001. Preference analyses of bird exploitation of the Horns Rev area showed that if the birds completely avoid the wind farm area after erection of the wind turbines, this will affect less than 1% of the various species, except divers where 1.58% will be affected. If the birds avoid the wind farm area and an adjacent 4 km zone (worst case scenario), it is estimated to affect 8-11% of the common scoter, 10% of the gannet, 7-9% of the divers, alcids and velvet scoter and 0-6% of the remaining species. The seasonal occurrence of the recorded species was fully comparable to the seasonal occurrence of these species recorded at Blaevandshuk since 1963. Year-to-year variation in abundance between the seasons August 1999 - April 2000 and August 2000 - April 2001 was mainly found in species that migrated through the Horns Rev area (terns, gannet, kittiwake), and with a less pronounced variation in staging and wintering species (divers, herring gull, common scoter). (au)