Directional Preferences of the Chiffchaff (Phylloscopus collybita) and the Robin (Erithacus rubecula) on Autumn Migration in the Beskid Niski Mountains (S Poland)

Data were collected at the "Akcja Carpatica" ringing station in the southern Poland in 2000-2003. In total 388 Robins and 357 Chiffchaffs were tested with the Busse's method (Busse 1995) for directional preferences during autumn migration. The data were elaborated using a non-standard calculation procedure proposed by Busse and Trocińska (1999) that could be applied to multimodal circular distributions.

Tested birds showed ca 69% (the Chiffchaff) and more than 60% (the Robin) of northern headings that we called "reversed directions" for autumn migration. We applied "reversing procedure", i.e. adding 180° to all northern directions. Such procedure was based on an assumption that birds show axial behaviour in the cage.

The species seasonal catching dynamics was divided into periods reflecting migration waves. Both studied species showed differentiation of directional preferences. In the Robin such directions as: SSE, SSW, ESE and WSW were noted. Most clear migration pattern was observed for the Chiffchaff — SSE and WSW directions dominated.

Although in both species sampling was short and irregular, the Chiffchaff migration pattern was clear and similar in all studied seasons. On the contrary, the Robin showed complicated and difficult to analyse headings' distributions. Robins indicated both intra- and interseasonal differentiation of directional preferences.