Das Vorkommen ausgewählter See- und Küstenvöogel vor Wangerooge während des Herbstzuges: der Einfluß von Windrichtung und Windstärke

摘要

Between 1995 and 1999 a study was made of the autumn migration of seabirds and coastal birds on the seaward side of Wangerooge Island (SE German Bight, East Frisian Islands; 53°47′N 07°54′E). Analyses are based on a total of 418 h on 118 days from 1 September to 15 November. Migration patterns in relation to wind direction and wind force are presented for 19 species. The patterns differed significantly from a hypothetical distribution. It proved possible to allocate the observed species to one of two groups, based on their occurrence patterns: 1. Those which migrated regularly and were wont to occur whatever the wind direction and wind force: divers, grebes, Great Cormorant, Common Shelduck, Barnacle Goose, Brent Goose, Great Scaup, Black Scoter, Common Eider, Sandwich Tern, Common/Arctic Tern, Little Gull, Common Guillemot and Razorbill. In general, their migration intensity is strongest during weak tailwinds (easterly winds) and during strong onshore winds from W/NW. Plainly, the latter case is not due to actual increase in migration intensity but is rather the result of birds being pushed closer to the coast while migrating farther out at sea. 2. Seabirds such as Northern Fulmar, Leach's Petrel, Sooty Shearwater, Northern Gannet and skuas occur chiefly or exclusively during gale-force winds from W or NW (weather system after passage of cyclones). The reasons for the observed patterns are discussed.