Coopers HawkGender determination and differential migration in Red-tailed Hawks (Buteo jamaicensis), Red-shouldered Hawks (Buteo lineatus), and Cooper’s Hawks (Accipiter cooperii)

Gender determination in the field can be difficult for many bird species because males and females have identical plumage. However, the two sexes often differ in size. In the three raptor species mentioned above, females are usually (but not always) larger than males. By comparing morphological data (measurements of physical characters) from males to that of females, we can determine the best measurements for researchers to use to sex individuals in the field. We use a genetic test to separate males from females in order to compare their measurements. By using a morphological method to sex individuals, we can then determine if the sexes migrate at different times through the Marin Headlands. We collaborate with the Golden Gate Raptor Observatory in the Marin Headlands, Lindsay Wildlife Museum Wildlife Hospital, the UC Davis Veterinary Teaching Hospital avian service, and others for both genetic samples and morphological data.