Natal dispersal and philopatry of Southeastern American Kestrels in Florida

Sex-biased natal dispersal is common among many bird species, with females usually dispersing farthest. The relative dispersal distances of male and female American Kestrels (Falco sparverius) are unknown. We examined natal dispersal in Southeastern American Kestrels (F. s. paulus) in north-central Florida, observing birds marked as nestlings with either color bands or patagial tags. Natal dispersal distances of 34 kestrels ranged from 0.0 to 38.5 km. Mean natal dispersal distance of females (8.6 km) did not differ significantly from that of males (8.3 km) (P = 0.43). We determined that no relationship existed for either sex between dispersal distance and subsequent reproductive success. However, the relationship between hatching date and dispersal distance was marginally significant (P = 0.071); fledglings from earlier nests were more likely to breed close to their natal area than were those from late-season nests. Our results suggest that natal dispersal and site fidelity in Southeastern American Kestrels are determined, at least in part, by inter- and intra-sexual competition for breeding sites.