Breeding, dispersal, and migration of urban peregrine falcons in eastern North America.

摘要

The recovery of the Peregrine Falcon (Falco peregrinus ) in eastern North America is a great conservation success, but the largely new urban population that it has produced has received remarkably little study. Satellite telemetry, detailed monitoring of active nests, and a review of archived nesting data since the resumption of breeding in the east were used to characterize aspects of the ecology of this rebuilding population.;In Ontario, the Peregrine Falcon population has grown to a record size, initially due to an intense captive-breeding and release effort, and more recently to considerable immigration from adjacent states. This influx resulted in a substantial dilution of the original F.p. anatum gene pool, in part because anatum juveniles appear to have been recruited to the breeding population at a lower rate. The, shift was also facilitated by a small number of immigrant adults producing a disproportionate percentage of the offspring in southern Ontario.;In southern Ontario, nearly all nests have been on buildings in cities, reflecting the dramatic expansion of Peregrine Falcons into urban habitat throughout eastern North America. Pooling data from southern Ontario, Quebec, Massachusetts, Pennsylvania, and New Jersey revealed that productivity varied considerably by region, but overall was similar at urban and rural sites. Within urban habitat, productivity was greater on buildings than on bridges and highest in nest boxes on covered ledges. While adults showed a bias toward nest sites facing between south and east, this did not translate directly into higher productivity, reflecting the complex variety of factors that influence nesting success. While building and vehicle collisions account for significant mortality among urban juveniles, human assistance through provision of nest boxes and rescues of grounded fledglings may offset these risks.;The accuracy of small satellite transmitters was confirmed to be appropriate for tracking long-distance movements, and they were used to compare the dispersal and migration of 34 Peregrine Falcons. Adults from Alberta migrated farther than juveniles from eastern North America. Among the juveniles, those raised at natural nest sites or in rural habitat departed earlier, while males were much more likely to migrate long distances than females. Siblings varied considerably in their migratory strategies, and the one juvenile tracked over multiple years adapted his behaviour annually, suggesting that there are many factors involved in determining migratory movements in Peregrine Falcons, and that their relative importance may change with time.