Is early dispersal enterprise or exile? Evidence from radio-tagged buzzards

In order to test whether Common Buzzards Buteo buteo that dispersed early w ere entrepreneurs or exiles, we determined standardised autumn ranges by ra dio-tracking 67 juveniles during 1990-94. Of these, 11 had dispersed more t han 2 km from their natal nest, and had therefore left the natal territory. Buzzards that dispersed early had more fragmented ranges than those that d elayed dispersal until the following spring; otherwise no range characteris tic differed between the two groups. When only the dispersers were consider ed, increase in distance from the natal nest was associated with a decrease in range size (r = -0.74) and an increase in the proportion of arable land within the range (r = 0.77). Further investigation revealed that range siz e was affected by distance from the nest but not by arable habitat. The sma ller range size of distant dispersers, combined with evidence of increased productivity among them, suggests that they were more likely to have been e ntrepreneurs than exiles.