Short distances moved by most avian natal dispersers and even shorter distances moved between adult breeding territories are thought to confer higher fitness. However, in a rapidly changing anthropogenic world experiencing extreme habitat loss, limited dispersal may become maladaptive if the affected area exhibits an ecological magnet effect. From 1997–2025, we studied natal and breeding dispersal of Swainson’s Hawks (Buteo swainsoni) in the Antelope Valley, California. Over the course of our study, we banded 276 nestlings and 28 adults. We confirmed natal dispersal distances of 33 of the 276 nestlings (median = 13.4 km, range 1.6-87.2 km). We observed 31 hawks breeding in more than 1 year; breeding dispersal distance ranged from 0.7 – 13.3 km (median = 1.3 km, n=15). The median natal dispersal distance of 13.4 km indicates the population is philopatric while the shorter breeding dispersal distance (median = 1.3 km) indicates strong nest-site fidelity, and both together suggest a high level of relatedness. Considering the rapid expansion of solar energy development and the fact that Swainson’s Hawk in the Antelope Valley are philopatric with a high degree of nest-site fidelity, this population may be vulnerable to a form of “philopatric” and/or nest-site fidelity-induced ecological trap.

Peter H. Bloom, Ph.D. is an internationally acclaimed raptor biologist, having spent more than four decades studying, banding, and tracking hawks, eagles, kites, condors, and owls, and working with landowners and the regulatory agencies in conserving their habitats. Dr. Bloom has published on the biology of raptors in more than 40 peer-reviewed scientific papers and technical reports and has spent over 1,000 hours conducting helicopter and fixed-wing nest survey work and aerial radio-tracking raptors. He is considered one of the best all-around field biologists in California with his extensive knowledge and experience with all terrestrial vertebrate groups and vascular plants.