Interrelationships within a raptor guild in the central Canadian Arctic

Abstract

The interrelationships of an arctic raptor guild comprising golden eagles (Aquila chrysaetos), gyrfalcons (Falco rusticolus), peregrine falcons (Falco peregrinus), rough-legged hawks (Buteo lagopus), and common ravens (Corvus corax) (a functional raptor) were studied from 1983 to 1986. Partitioning of time, space, and food generally related to body size; small-bodied species (peregrines and rough-legged hawks) nested later, had shorter reproductive periods, used smaller cliffs with less overhang, and took smaller prey than large-bodied species. The raven, a passerine, was often the exception. The onset of laying for each raptor was closely related to arrival or emergence of major prey species. Gyrfalcons and ravens selected well-protected sites, while other species selected sites with southerly aspects but little overhang protection. Overlap in prey use was high between eagles and gyrfalcons early in the breeding season. The spacing of all species except the rough-legged hawk tended to be regular, apparently as a result of intraspecific rather than interspecific factors. However, all species tended to nest far from occupied eagle sites. Reproductive success was not affected by distance to nearest intra- or inter-specific neighbor, except among gyrfalcons whose reproductive success was significantly lower when conspecifics nested within 5 km than when they nested farther away. Golden eagles, a species on the edge of its geographic range, had the lowest reproductive success of all species.