Ecological background of the raptor-gamebird conflict: raptors as limiting factors of gamebird populations

55 pages.-- REGHAB Project: Report on Workpackage 3 – Deliverable no 5.The traditional Erringtonian view suggested that predators are generally not harmful to prey populations as they only take a doomed surplus of the prey population (Errington 1956). It was also frequently assumed that the predated individuals were ill, injured or otherwise of low quality and that predators acted as health officers in nature. This view has, however, been questioned in many studies conducted during 1980s and 1990s, and recent studies indicate that predation may, at least under certain environmental conditions, have profound effects on vertebrate prey populations (Marcström et al. 1988, Newton 1993, Krebs et al. 1995, Korpimäki and Krebs 1996, Tapper et al. 1996, Hubbs and Boonstra 1997, Korpimäki and Norrdahl 1998, Byrom et al. 2000, Thirgood et al. 2000b, Korpimäki et al. 2002). From a theoretical point of view, predators can either stabilise or destabilise prey populations, depending on the type of responses of the predator and carrying capacity of the prey (e.g. Hanski et al. 1991, Sinclair and Pech 1996). Increasing rate of generalist predation decreases the length and amplitude of the prey cycle which is driven by specialist predators, and with high enough density of generalist predators the prey cycle turns to a stable equilibrium point (Hanski et al. 1991).REGHAB Project is funded by European Union Contract No. EVK2-CT-2000-200004 within the 5th Research Framework Program.Peer reviewe