Prey of Peregrine Falcons Breeding in West Greenland

Abstract

Previous studies on the diet of Peregrine Falcons (Falco peregrinus) in Greenland were based primarily on prey remains, an indirect technique that may produce biased results. Earlier estimates of prey biomass are too general and speculative to be conclusive. No other study provided data on the age of prey species or showed that Rock Ptarmigan (Lagopus mutus) can be an important component in the diet of Greenland peregrines. We used direct observations of prey deliveries and collection of prey remains to assess prey (in terms of frequency of occurrence and biomass) of breeding Peregrine Falcons in West Greenland. We also determined prey selection in relation to local prey availability. During 492 hr of observation at two eyries we found that four small passerines—Lapland Longspur (Calcarius lapponicus), Northern Wheatear (Oenanthe oenanthe), Common Redpoll (Carduelis flammea), and Snow Bunting (Plectrophenax nivalis)—contributed over 80% of the prey items delivered, with the longspur being the principal prey species in terms of frequency of occurrence and biomass. However, ptarmigan contributed almost as much biomass as longspurs at one eyrie. Fledglings of all these bird species provided the majority of items and biomass at both eyries. Analysis of 676 prey items from prey remains at 159 eyries showed similar frequencies and rankings for the prey species comprising the majority of the diet of Peregrine Falcons as determined by prey deliveries. Lapland Longspur was taken in proportion to its availability near two eyries; ptarmigan and Snow Buntings were taken more frequently than expected. Local differences in prey use (especially ptarmigan) were found.