Killing of raptors on grouse moors: evidence and effects

Abstract

Owing to the intensity of game management in Britain, managers of grouse moors have illegally killed raptors to increase the numbers of Red GrouseLagopus l. scoticaavailable for shooting. This paper summarizes evidence for the recent scale of illegal raptor killing on grouse moors and its effects on populations. It provides insights into how raptors themselves respond demographically to different levels of killing. Over Britain as a whole, most raptors have increased and expanded considerably since the 1970s, in response to reduced killing and nest destruction, and the diminished impacts of organo‐chlorine pesticides; however, in recent decades the populations of some species have declined on and around grouse moors. This is widely evident in Hen HarrierCircus cyaneus, Peregrine FalconFalco peregrinusand Golden EagleAquila chrysaetospopulations and in more restricted areas also in Northern GoshawkAccipiter gentilisand Red KiteMilvus milvuspopulations, in all of which illegal killing has been sufficient to affect numbers over wider areas. The evidence consists mainly of: (1) greater disappearance of nesting pairs, lower breeding densities or reduced occupancy of apparently suitable traditional territories on grouse moors compared with other areas; (2) reduced nest success compared with other areas; (3) reduced adult survival compared with other areas; (4) reduced age of first breeding, reflecting the removal of adults from nesting territories and their replacement by birds in immature plumage; (5) greater levels of disappearance of satellite‐tracked birds on grouse moors than elsewhere; and (6) the finding of poisoned baits and traps, and shot or poisoned carcasses of raptors. Not all these types of evidence are available for every species, and other types of evidence are available for some. The Common BuzzardButeo buteois currently the most numerous raptor in Britain and also seems to be killed in the greatest numbers. Other raptor species, including MerlinFalco columbarius, Common KestrelFalco tinnunculusand Eurasian SparrowhawkAccipiter nisuswhich nest on or near grouse moors, have little or no significant impact on grouse and are killed less often or not at all. In the absence of illegal killing, some raptor species breed as well or better on grouse moors than in other habitats. Merlins, in particular, seem to thrive on grouse moors, benefiting from the management involved (including predator control). Other aspects of illegal raptor killing are discussed, including suggestions for ways in which it might be reduced.