Published in support of the UK Biodiversity Action Plan for black grouse

Causes of decline

Predation

The main predators of black grouse eggs and chicks in Britain are carrion and hooded crows, stoats and foxes. Foxes and some bird of prey species (golden eagles, goshawks, hen harriers and peregrines) will take juvenile and adult birds, while a range of other predators (such as jackdaws, magpies, weasels and pine martens) will take eggs if the opportunity arises. The importance of these predators on the black grouse populations varies regionally.

Over recent decades, predation pressures on black grouse could have increased as the populations of some predator species have increased. However, predation risk may also have increased as a result of habitat changes and fragmentation, which could make black grouse more vulnerable (short vegetation increasing their exposure, for example).

Studies in northern Europe (Angelstam 1984; Willebrand 1988) have shown that the density and breeding success of black grouse increased following a reduction of fox and pine marten numbers, while elsewhere in Sweden and Norway, increases in black grouse were correlated with a large reduction in fox numbers during an outbreak of sarcoptic mange. As the fox population recovered in Sweden, there was a corresponding decrease in black grouse numbers. Other studies in this region have found less evidence of predation effects, but overall there is compelling evidence that, in some situations, predation limits density.

Whilst an effect of predation on black grouse breeding density has yet to be demonstrated in the UK, removing carrion crows did increase breeding success at Abernethy Forest in Scotland. Thus, the general findings from Fennoscandia probably apply to the UK.

Further assessment of the role of predation may arise from a study at Palé Moor, in north Wales, following a period of no predator control but continued habitat management. An ongoing experimental study at Otterburn and Ray Demesne in Northumberland, by the Game & Wildlife Conservation Trust, aims to assess the role of gamekeepers in controlling predators, and how this might affect moorland bird species. The final data is due to be collected in spring 2008.

Habitat restoration is critical to increasing black grouse numbers in the long-term, but reducing predation is necessary to facilitate the recovery of black grouse in most places.

What can be done?

Other factors in the decline
Agriculture
Deer
Fencing
Forestry
Shooting
Weather