Directional behaviour of the Sedge Warbler ( Acrocephalus schoenobaenus ) studied in two types of orientation cages during autumn migration - a case study

Abstract

Migratory directions of Sedge Warblers tested in the Emlen funnel and Busse's flat cage during autumn migration in the Balkan region were studied. Some methodological aspects of orientation data analysis were discussed as well. According to orientation data at least two populations of the Sedge Warbler migrate in NE Bulgaria: one in SW direction via Greece, crossing the Mediterranean Sea to Libya, and then Central Africa and second one through Turkey, (Cyprus?) and the Middle East to the eastern parts of winter quarters (SE direction). This pattern is clear when a calculation method that assumes reverse and axial behaviour of birds ( i.e. reversing vectors from northern sectors) is applied. Nature of "reverse migration" is still not well recognised and seems to be very interesting for further studies.