Long-term changes in the abundance and breeding success of raptors and ravens in periods of varying management of a Scottish grouse moor
Management of heather moorland for driven Red Grouse (Lagopus lagopus scotica) shooting in the British uplands may benefit some raptors by reducing predation risk, especially when breeding, and by increasing food availability. We describe changes in abundance and breeding success of four raptor species and Common Raven (Corvus corax) during a 27-year study on a grouse moor in southwest Scotland in relation to whether or not the moor was managed by gamekeepers. Ground-nesting raptors, Hen Harrier (Circus cyaneus) and Merlin (Falco columbarius), increased during periods of grouse moor management and had a higher proportion of successful nesting attempts. Predation was the main apparent cause of breeding failure. In contrast, grouse moor management did not influence either abundance or breeding success of tree- and crag-nesting species, i.e., Peregrine (Falco peregrinus), Common Buzzard (Buteo buteo), and Raven. Buzzard sightings increased during the study, in line with their national recovery, whereas Peregrine and Raven showed little change in abundance. The results of our study highlight that management for Red Grouse can benefit both Hen Harrier and Merlin. However, on a UK scale these benefits to Hen Harriers, but not Merlin, are outweighed by their illegal killing, caused by fears that their consumption of Red Grouse can undermine the economics of grouse moor management.