WIND-INFLUENCED JUVENILE DISPERSAL OF SPANISH IMPERIAL EAGLES

The effect of wind on dispersal directions of 21 young Spanish Imperia l Eagles Aquila adalberti that were equipped with radio-transmitters a t the end of their nestling period from 1986 to 1988 in Donana Nationa l Park (southwestern Spain), was analyzed. Two preferential directions were found. Except for winds blowing towards the sea, which is visibl e from the natal population, the distribution of first departures was coincident with the wind directions on the dates of departure. There w as no trend among siblings towards dispersing in the same direction. S ubsequent departures by young eagles from the natal population were al ways in the same direction as their first departure and were not influ enced by wind direction. These results suggest that environmental fact ors, more than inheritance, determine individual differences in the us e of particular dispersal areas, and that these differences may persis t throughout life.