Natural history of the peregrine falcon in the Keewatin District of the Northwest Territories

Abstract

Mean internest distance of 3.3 km represents the highest nesting density on record for the species in the Arctic. Both timing of arrival on the breeding grounds and clutch initiation are influenced strongly by spring weather patterns. Nineteen species of birds and 3 species of mammals were used as prey; but in most years the bulk of the diet consisted of 6 species of birds and 1 mammal. A dramatic increase in the density of territorial peregrines in a year of high microtine rodent abundance, coupled with changes in various measures of reproductive performance, suggested that use of lemmings by falcons can be significant in some years. Suggestions that peregrines lay fewer eggs in the arctic part of their range were not supported. Broods hatched asynchronously, with the last-hatched young dying in c 1/2 of all broods of 4. Surviving last-hatched young in broods of 4 grew at rates similar to older nest mates. -from Authors