Predatory responses of a raptor guild to changes in prey density

Abstract

The responses of a guild of open-country birds of prey to changes in prey density were studied on a simple island habitat in southern Ontario. Numerical responses were conspicuous in all species, while functional responses were weak. Individual raptor species displayed characteristic responses, differing from others in intensity and aspects of seasonality related to breeding versus wintering. Yet a basic similarity in the form of response for all species present at any one season, and a complementarity of responses of species present through the changing seasons, resulted in an overall guild level pattern of numerical and functional response of predators to changes in prey density. The synchronous fluctuations of predator and prey densities observed are similar to those of arctic areas and unusual for the temperate regions where the study was conducted. Characteristics of the predator and prey assemblages and features of the study site were important in determining the type, the intensity, and the level (species or guild) at which the responses were exhibited.