Can raptor predation limit or regulate grouse populations? I. Functional and numerical response of raptors
Redpath, S.M. & Thirgood, S.J. 1997: Can raptor predation limit or regulate grouse populations? I. Functional and numerical response of raptors. - Wildl. Biol. 3: 288.
Hen harriers Circus cyaneus and peregrine falcons Falco peregrinus on heather Caluna vulgaris moorland managed for red grouse Lagopus lagopus scoticus in Britain are killed illegally by gamekeepers because they believe these raptors have a significant impact on grouse populations and shooting bags. A 5-year study of raptor-grouse dynamics was conducted to examine how diet of hen harriers and peregrine falcons varied in relation to the availability of grouse and other prey (the functional response). Further, we considered how numbers of breeding and hunting raptors varied within and between areas in relation to grouse and other prey availability (the numerical response). Hen harriers showed a functional response to grouse abundance, and both species hunted in relation to grouse abundance in winter but not in summer. Neither hen harriers nor peregrine falcons appeared to respond numerically in terms of breeding numbers.
Key words: Britain, Circus cyaneus, Falco peregrinus, hen harrier, Lagopus lagopus scoticus, peregrine falcon, predation, red grouse
Stephen M. Redpath, Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, PE17 2LS, United Kingdom
Simon J. Thirgood, The Game Conservancy Trust, Crubenmore Lodge, Newtonmore, Inverness-shire, Scotland, PH20 1BE, United Kingdom