© 2017, Dt. Ornithologen-Gesellschaft e.V. In birds, integrated levels of corticosterone (CORT) measured in feathers (CORTf) allow us to make inferences on past levels of stress demands. It has been suggested that levels of CORTf track carry-over effects across seasons. Nevertheless, our understanding of how this measure can be used to assess future health status is far from complete. In this study, we aimed to investigate whether CORT deposited in feathers over the moulting period was related to subsequent mortality and health status in wild raptors admitted to rehabilitation centres. Thirty-four Eurasian Sparrowhawks (Accipiter nisus) admitted during the non-moulting period were sampled. Body condition (BC) was used as an indicator of health status to classify individuals’ health as good, poor or cachexia depending on their pectoral muscle score. Mortality was recorded over the non-moulting period. Other potential sources of CORTf variation were assessed, such as sex, age and feather type, primary or body covert feathers. While CORTf did not vary with age or sex, significant differences were found between primary and body feathers, highlighting the importance of sampling the same feather type. Our results also revealed that birds in poor BC showed higher CORTf levels than individuals in good condition; however, CORTf levels in cachectic birds did not differ from those in good condition. This finding suggests caution when assuming that only high CORTf levels represent individuals in poor condition, and limits the utility of CORTf for the prediction of BC. The present study also showed that individuals which died following admission had higher CORTf levels than individuals which survived, suggesting the potential utility of CORTf as a metric for the study of subsequent mortality.
- Body condition
- Carry-over effects