News

Evidence Mounts that Predator Removal on Grouse Moor

18th November 2004

THE impact of predator removal on ground nesting birds in a moorland habitat, other than red grouse, has never before been quantified.

However the Upland Predation Experiment, currently being undertaken by researchers at The Game Conservancy Trust, is investigating whether the removal of common predators, such as foxes, stoats, weasels and crows can increase breeding success and ultimately increase the population size of a range of ground nesting bird species on moorland and the surrounding marginal farmland.

Britain’s moorland supports an important range of breeding birds, including wader species such as the lapwing which has suffered serious declines since the 1970s and the curlew which is also on the UK’s ‘amber list’ due to declines across Europe. There are also species such as the golden plover which are currently stable in numbers but which only breed on moorland. A large proportion of Britain’s moorland is managed for grouse shooting which includes the removal of the common predators.

The project itself consists of four study areas, each measuring 12 square kilometres (1,200 hectares), which have all been monitored since 2000. After an initial breeding season with no predator removal on any plots, predator removal by gamekeepers has been undertaken on two plots, with the remaining two plots being unkeepered to provide a comparison. All other influences such as grazing and heather burning have been kept constant so that the focus is on the effect of predator removal alone.

As the fourth full year of data collection draws to a close, the initial findings indicate that keepering activities reduce the numbers of the main predators and this appears to be having a positive effect on the breeding success and population size in some of the ground nesting bird species.

In addition to recording dramatic increases in breeding success and a four-fold rise in the numbers of red grouse, the wader species have been fairing well on the keepered plots. In particular the breeding success of lapwing, curlew and golden plover has been better on the keepered plots, both when compared with before keepering started and compared with the unkeepered plots. In lapwing and golden plovers the numbers of breeding pairs is also 50% higher than before keepering commenced.
For the smaller ground nesting birds such as the meadow pipit breeding success appears to be higher when predators have been removed, but at the moment the trends in abundance of small passerines are not clear in relation to predator removal.

The main focus of the monitoring has been on the more abundant ground nesting species such as red grouse, lapwing, curlew, golden plover, meadow pipits and skylarks. In addition, the less frequently found species such as black grouse, grey partridge, wheatear, whinchat, stonechat, dipper, short-eared owls and hen harrier, are being recorded and will be included in the final analysis.

The Upland Predation Experiment is planned to last eight years, and has now reached the half-way point. Although one of the keepered plots will remain keepered to look at longer term effects, the gamekeeper from the second keepered plot is moving his activities to one of the unkeepered plots. Dr Baines, the Trust’s Director of Upland Research explained:

“By moving the keeper to a new plot we can check that the same trends in breeding success and population size occur on different study areas, in addition to monitoring what happens when predator removal stops. The next four years of the experiment will be crucial to identify whether reducing the number of local predators is one of the major catalysts that will help to conserve ground nesting birds in the uplands.”

From a moorland conservation perspective, the end of the experiment in 2008 will be an important landmark for all those involved in determining future conservation policy for all precious upland species.


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