The orientation behaviour of chaffinches, Fringilla coelebs, caught duringactive migratory flight, in relation to the sun

The few orientation studies that have been carried out with day-migrating b irds show that they are able to use solar and magnetic orientation cues for orientation. Previous orientation experiments in Emlen funnels have been c arried out either with hand-raised birds or with birds caught during restin g periods at stop-over sites. The aim of our study was to test whether bird s caught during active flight show a higher concentration of migratory acti vity in the seasonally appropriate migratory direction in the funnels than birds that had not experienced migration just before the funnel experiments . The topography at the alpine pass Cot de Bretolet at the border of Switze rland and France allowed us to capture birds during active migratory flight . These birds were in full migration disposition. Orientation experiments w ith chaffinches suggested an influence of the sun because chaffinches did n ot orient in the seasonally expected direction, but probably showed positiv e phototaxis towards the light of the sun at the opposite side of the funne l. Chaffinches tested under overcast conditions oriented to the north-west which probably was a 'nonsense' orientation and not a reverse migration or compensatory behaviour. We conclude that freshly caught birds are too stres sed to show appropriate orientation when tested immediately after catching.