Dynamics of Autumn Migration of the Acrocephalus Warblers Through the Polish Baltic Coast

Abstract

Dynamics of Autumn Migration of the Acrocephalus Warblers Through the Polish Baltic Coast We analyse in our paper the autumn migration of five warblers: i.e. the Reed Warbler (Acrocephalus scirpaceus), Sedge Warbler (A. schoenobaenus), Marsh Warbler (A. palustris), Great Reed Warbler (A. arundinaceus) and Aquatic Warbler (A. paludicola), through the Polish Baltic coast. Data were collected in 1962-2005 at two stations: Bukowo-Kopań and Mierzeja Wiślana, as well as (for a comparison) at the Drużno station in 1990-2002 and 2003-2005. The most numerous species caught at all the stations was the Reed Warbler, whereas the Aquatic Warbler was caught only sporadically. Long-term number dynamics from Bukowo-Kopań and Mierzeja Wiślana showed considerable fluctuations for the first four species, which could have been influenced by weather or habitat changes, or they could have reflected long-term population cycles. Strong correlations between the numbers of species preferring reeds might indicate habitat basis of the fluctuations. Seasonal migration dynamics were also similar, with the peak of migration in mid-August. However, the dynamics from Drużno suggested that the real peak of migration occurred earlier. Median dates of the Reed Warbler migration at Bukowo-Kopań showed marked fluctuations, whereas at Mierzeja Wiślana they were delayed significantly; these changes were probably connected with climate changes.