As the start of the red grouse shooting season approaches, a new scientific study by the Game & Wildlife Conservation Trust (1) and published in the Journal of Applied Ecology (2), identifies that the control of predators such as foxes and crows, carried out to protect red grouse, can benefit one of our most striking birds of prey - the hen harrier.
This study is the first to show how grouse moor management can help hen harrier productivity by protecting the harrier from predators and boosting its natural moorland food supply. But it highlights a conservation conundrum as high densities of harriers can prevent successful management of productive grouse moors. This has led to illegal control reducing the conservation status of this much-acclaimed bird of prey.
Within the study, which was carried out between 1992 and 2007 at Langholm, a grouse moor in southern Scotland, researchers from the Game & Wildlife Conservation Trust compared numbers and productivity of hen harriers in relation to a change in control of foxes and crows on the moor managed for red grouse shooting.
During this period, hen harrier numbers increased from two breeding females in 1992 to 20 birds in 1997. In 1999 grouse management and its associated predator control was stopped following the heavy losses of red grouse because of harrier predation. Carrion crows and red foxes then increased and numbers of female harriers dropped to just four from 2002 onwards with predation by foxes cited as the main cause of harrier breeding failure.
Grouse moors can bring conservation benefits not only to harriers but also to globally important heather moorland habitats and other important ground nesting birds such as lapwing, golden plover and curlew (3). If this management for grouse were to stop it could exacerbate the current declines of these internationally important upland bird species and heather moorland habitats.
Despite raptors in general being protected by law in the UK since 1954, an important factor restricting the range and number of breeding harriers is probably their persecution on grouse moors to conserve grouse stocks in Scotland and northern England.
For the future benefit of the hen harrier population the study clearly identifies the importance of finding ways to ensure that grouse moors are managed for harriers while still being economically viable.
Dr David Baines, the GWCT’s Upland Director of Research and lead author of the study said, “Supported by well-documented research, it is known that hen harriers can increase to densities whereby they reduce numbers of grouse and thus cause a moor to become financially unviable.”
Dr Baines continued, “Devising techniques that can be put in place to reduce the impact of harriers on grouse would mean that harriers could breed more successfully on grouse moors where their natural predators such as carrion crows, hooded crows and red foxes, which predate clutches, chicks or even adults, are legally killed by gamekeepers on grouse moors to optimise grouse stocks.”
The study concludes that to mitigate the impact of harriers on grouse populations, several techniques are being tested. These include introducing a ‘harrier quota’ principle, which would limit the number of young harriers in an area through non-lethal means and diversionary feeding of nesting harriers with supplementary food such as dead rats or day-old poultry chicks.
Dr Baines concludes, “Successful implementation of these measures on grouse moors may be a way forward to protect hen harriers. As we have shown, the control of generalist predators by gamekeepers not only helps conserve important species of ground-nesting birds and grouse but is also beneficial for our spectacular hen harrier. The argument is compelling and dialogue between shooting and conservation bodies is crucial to ensure the future of this magnificent bird of prey. It is therefore gratifying that stakeholders on both sides of the debate have recently expressed their desires to work collectively towards finding answers.”
Photocredit: Laurie Campbell. Photocaption: A study by the Game & Wildlife Conservation Trust suggests that diversionary feeding of nesting hen harriers with supplementary food such as dead rats or day-old poultry chicks could reduce the impact of harriers on grouse populations.
Notes to editors
1) The Game & Wildlife Conservation Trust is an independent wildlife conservation charity which has carried out scientific research into Britain’s game and wildlife for the past 70 years. We advise farmers and landowners on improving wildlife habitats and we lobby for agricultural and conservation policies based on science. We employ 20 post-doctoral scientists and 40 other research staff with expertise in areas such as birds, insects, mammals, farming, fish and statistics. We undertake our own research as well as projects funded by contract and grant-aid from Government and private bodies. The Trust is also responsible for a number of Government Biodiversity Action Plan species and is lead partner for grey partridge and joint lead partner for brown hare and black grouse. For Information, contact: Morag Walker – Head of Media, Telephone – 01425-652381 (direct 01425-651000) Mobile – 07736-124097 www.gwct.org.uk
2) This study, ‘Hen Harriers on a Scottish grouse moor: multiple factors predict breeding density and productivity by Dr David Baines, Upland Research Director with the Game & Wildlife Conservation Trust is published online by the Journal of Applied Ecology and can be downloaded at Hen harriers on a Scottish grouse moor: multiple factors predict breeding density and productivity J. App. Ecol. DOI: 10.1111/1365-2664.12154.
3) Taken from a study published in the Journal of Applied Ecology, 47, 263-273 ‘Changes in breeding success and abundance of ground-nesting moorland birds in relation to the experimental deployment of legal predator control” by Dr Kathy Fletcher et al from the Game & Wildlife Conservation Trust.
- Heather moorland is rarer than rainforest and threatened globally – 75% of what is left is found in Britain because it is managed for red grouse
- Heather moorland managed for grouse supports up to five times as many threatened wading birds as moors not managed by gamekeepers
- Grouse moor managers have created habitats for 95% of the surviving black grouse population in England
- Managing the heather helps preserve the biggest carbon store in the UK found in the underlying peat