What banding tells us about the movement ecology of raptors

Abstract

We examined banding encounter records from 1920 to 2006 for three raptors that are commonly banded in North America: American Kestrel (Falco sparverius, 4707 encounters), Sharp-shinned Hawk (Accipiter striatus; 5256), and Cooper's Hawk (A. cooperii; 3848). We selected birds banded during summer or autumn migration and encountered during winter to investigate movement distances and winter latitudes by sex, age, year banded, banding latitude, and flyway. Female American Kestrels migrated farther than males, but travel distances did not vary by age. Distance moved to wintering sites declined with encounter year for American Kestrels, suggesting that migratory short-stopping may be occurring across North America. Movements of the three species typically showed a chain migration pattern; however, female American Kestrels from the most northern latitudes demonstrated a leapfrog pattern, moving beyond mid-latitude birds to more southerly wintering latitudes. Female American Kestrels and Cooper's Hawks moved farther than males, whereas Sharp-shinned Hawk migration distances did not vary by sex. Hatch-year Sharp-shinned and Cooper's hawks moved farther than after-hatch-year birds, whereas no age difference was observed for American Kestrels. For all three species, northern-latitude birds moved farther than mid- or low-latitude birds, and low-latitude birds appeared to be largely resident. Distances moved also varied by flyway for both accipiters. © 2012 The Raptor Research Foundation, Inc.