SEEN - SE European Bird Migration Network
Orientation behaviour of three passerine trans-Saharan migrants: influence of meteorological factors and physiological condition

Mihaela Ilieva, Pavel Zehtindjiev
Institute of Zoology, Bulgarian Academy of Sciences, Bulgaria

Realization of bird migration is known to depend on weather situation as well as physiological condition of the individuals. Using two types of cages, Emlen funnels and Busse cages, three species of trans-Saharan migrants: the Sedge Warbler (Acrocephalus schoenobaenus), Great Reed Warbler (A. arundinaceus) and Willow Warbler (Phylloscopus trochilus) were tested in order to reveal the influence of meteorological factors and physiological condition on their orientation. During the autumns of 2001 - 2004, we performed daytime and night orientation experiments at Kalimok Field Station (41o00?N 26o26?E, NE Bulgaria) with 1074 birds of these species. For the three analyzed factors ? cloudiness, fat level and breast muscle size, clear tendencies, typical for the all species studied were not registered. For the Sedge Warbler and Willow Warbler testing under clear sky during the day leads to increase of NW direction. Birds from the same species with high fat reserves show more southern orientation. Increase in NW direction was registered for great reed warblers with increase of fat level and muscle size. In night tests decrease of seasonal inappropriate directions for willow warblers and increase of southern directions for sedge warblers was observed under clear sky. Sedge warblers with high fat and muscle score showed more southern directions. The results obtained indicate difference in the factors? influence, depending on the species and testing time ? day or night.

Created by Pronetix 2006