Branta Issues > Issue №8 (2005)

Autumn migrations of the Sedge Warbler (Acrocephalus schoenobaenus) in the western Ukraine

O.S. Zakala

The dynamics of daily capture of the Sedge Warbler during summer-autumn appear as a curve (fig.3), which is strongly influenced by the weather conditions (often with negative impact) and by the level of birds fat reserves. Migration intensity (MI) varies in different years and depends on the climatic conditions, food supply and physiological conditions of a bird. The highest migration intensity of the Sedge Warbler during 1995-2002 was noted in 1996 (2.27 birds per net), the lowest - in the 1997 (0.52) (fig.7). The highest MI was noted just after dawn (between 6:00 and 7:00 AM - 24.8% of all birds), when birds stopped after the night migration, and small peak in the evening (3.9%) that is caused probably by the increased activity of the night migrants (fig.4). The daily migratory intensity is influenced by the temperature and precipitation. No birds were trapped when the temperature is high or during the rain (fig.5, 6). The increase of the fat score of birds is evident from the end of August - beginning of September (fig.9). Adult specimens of the Sedge Warbler, which were trapped during migration, have higher fat score (fig.8) and mean weight (p<0.01) (Table 4) than youngs (Table 3). Adult specimens start to migrate earlier, and already at the middle of September only young birds constitute the migratory flocks (fig.2). Latter stay for a longer time on the migration stopover. The postbreeding dispersion is characteristic for young specimens of the Sedge Warbler. During the migratory period these birds do not have completely developed wings and tail. According to the ringing and recovery data we can state that the birds from the Northern Europe fly through the territory of the western Ukraine, and that the birds from the western Ukraine fly to the south-west direction. Three birds from Estonia and one from Finland were recorded in "Cholgyns’ky Ornithological Reserve". One bird from "Cholgini" was found in Hungary (fig.10).