Seasonal Dynamics of Testosterone and Corticosterone in Predatory Birds as Exemplified by the Northern Goshawk (Accipiter gentilis).

Testosterone and corticosterone are steroid hormones that regulate various aspects of bird behavior. The dynamics of blood level of these hormones depending on the stage of the life cycle have been studied in many species. It has been shown for both sexes that the levels of both hormones rise during the breeding season. We have studied changes in the level of these hormones in the northern goshawk (Accipiter gentilis) during a year. This has been the first study of this type on northern goshawk. We collected blood samples from 16 adult northern goshawks kept in pairs in aviaries in the VITASFERA Rare Bird Species Breeding Center. The testosterone level rises in males during the period of lekking and mating (March-June); however, there is no synchronous increase in females. The corticosterone level generally remains high throughout the year in both sexes. Since these are the only data on the northern goshawk, it cannot be concluded whether this is characteristic of the species as a whole or only for captive birds.