The Diet of Peregrine Falcons in Rankin Inlet, Northwest Territories: An Unusually High Proportion of Mammalian Prey

Abstract

Throughout their virtually world-wide range, Peregrine Falcons (Falco peregrinus) rely almost completely on the aerial capture of other birds (Cade 1960, Radcliffe 1980). Moreover, the Peregrine's reliance on a wide range of stable avian prey populations is believed to be responsible for the great stability of their breeding density and reproductive output (Newton 1979, Ratcliffe 1980). In our study area near Rankin Inlet, Northwest Territories, Canada, however, Peregrine Falcons are not very stable in either breeding density or reproductive output. The number of successful pairs rose from a three-year mean of 13 to 21 and production of fledglings nearly doubled in conjunction with a 1985 peak in microtine rodent density (Court et al. 1988a, 1988b). The authors speculated that the microtine increase provided an abundant food resource that the Peregrine Falcons exploited to their reproductive advantage. A subjective appraisal of prey use during the microtine peak year indicated that both microtine rodents and arctic ground squirrels were being eaten (Court et al. 1988a). We wanted to determine if mammals were a normal prey species for the Rankin Inlet Peregrine Falcon population. Therefore, in this paper, we quantitatively describe the diet of Peregrine Falcons of Rankin Inlet during two years of non-peak microtine abundance. METHODS