Is Early Dispersal Enterprise or Exile? Evidence from Radio-Tagged Buzzards

In order to test whether Common Buzzards Buteo buteo that dispersed early were entrepreneurs or exiles, we determined standardised autumn ranges by radio-tracking 67 juveniles during 1990-94. Of these, 11 had dispersed more than 2 km from their natal nest, and had therefore left the natal territory. Buzzards that dispersed early had more fragmented ranges than those that delayed dispersal until the following spring; otherwise no range characteristic differed between the two groups. When only the dispersers were considered, 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 size was affected by distance from the nest but not by arable habitat. The smaller range size of distant dispersers, combined with evidence of increased productivity among them, suggests that they were more likely to have been entrepreneurs than exiles.