Auteur: Gregor Scheiffarth
Datum: 25 april 2003
Universiteit: Universität Oldenburg

Although large numbers of birds visit the Wadden Sea each year, consumption by birds amounts only to 8.7 g AFDM m-2 a-1 which equals 10-25 % of the secondary production. A main consumer is the Bar-tailed Godwit. In the Wadden Sea a European and an Afro-Siberian population of Bar-tailed Godwits stopover on their migration between wintering and breeding areas. Birds of the European population stayed during spring stopover for 30-40 days in the study area. Birds were extremely site faithful to their spring stopover site showing an annual mortality of 17-26 %. The use of the northern Wadden Sea as a wintering site is mainly determined by thermostatic costs, which are smaller for females than for males resulting in a female bias during winter. Deciding for northern wintering forms a trade off between energetically cheap wintering and behaviourally avoiding movement to unknown places. On spring migration, European birds follow an energy minimizing and Afro-Siberian birds a time minimizing strategy with much higher energy demands. Afro-Siberian birds could follow this strategy by investing as much time as possible in foraging and keeping to a strict, well timed schedule.

Download the complete thesis: Born to fly - migratory strategies and stopover ecology in the European Wadden Sea of a long-distance migrant, the Bar-tailed Godwit (Limosa lapponica)
(pdf 2 Mb).