AGE AND SEX DIFFERENCES IN THE TIMING OF FALL MIGRATION OF HAWKS AND FALCONS

摘要

We trapped more than 23,000 migrating raptors at Cedar Grove, Wisconsin during the autumns of 1953-1996, permitting accurate identification of age and sex. Adults migrated significantly later than juveniles in 8 of 10 species, and males migrated later than females in 7 species. We suggest that it is adaptive for adults and males to remain on breeding territories as long as possible. Adult Peregrine Falcons (Falco peregrinus) migrated before juveniles. There was no age difference in migration of Rough-legged Hawks (Buteo lagopus). Both species breed in the Arctic where the brief breeding season requires that adults leave a son as possible So adults might then migrate more rapidly than juveniles.