Meeting Abstract
Raptors, or birds of prey, are birds characterized by precise vision, talons, and powerful beaks that are used to prey upon other animals. Though stress and fluctuating asymmetry have been examined in other avian species, often within the context of sexual selection and honest signals, it has not been closely examined in birds of prey. Corticosterone and its metabolites can be successfully measured from flight feather samples and are thought to be indicative of the stress experienced by birds during molt, when they are first growing the feather. In our study, we recorded structural measurements of paired limbs from each bird admitted to the Illinois Raptor Center and measured corticosterone in the feathers of juvenile and adult red-tailed hawks (Buteo jamaicensis), Cooper’s hawks (Accipiter cooperii), and barred owls (Strix varia). We then used an analysis of covariance to determine effects of age and feather corticosterone levels on fluctuating limb symmetry. Because we are also interested in the consequences of asymmetrical growth, we also compared differences in symmetry between birds admitted with and without broken bones. We found a positive correlation between fluctuating asymmetry and corticosterone levels in immature birds but not in adult birds. Birds admitted with broken bones also had more fluctuating asymmetry. These relationships indicate that high levels of stress during development can increase fluctuating asymmetry in immature birds which, in return, may lead to decreased survival
