Red Grouse and Their Predators

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correspondence Red grouse and their predators Sir — We read with interest articles by May1 concentrated near young plantations4 and 2 6,000 and Mead on the persecution of hen Langholm red grouse are birds of open moorland. harriers and the impact of raptor predation 5,000 Moor ‘F’ Finally, how can conflicts between on grouse-shooting bags. Some of Mead’s Moor ‘G’ raptors and grouse shooting be resolved1? 4,000 comments, however, are misleading2. As suggested by Mead6, predation patterns Mead suggests that the economic effects 3,000 observed at Langholm will not apply of harriers on grouse shooting are minimal. 2,000 everywhere. Our data suggest that, in the Unfortunately, that is not always the case. bag Grouse absence of persecution, harrier numbers We recently completed six years of research 1,000 will be related to densities of prey other on harrier and peregrine predation on 0 than grouse3. In the long term, reducing the 3 1975 1980 1985 1990 1995 2000 grouse at Langholm in southwest Scotland . Year amount of grassland on moors may reduce Raptors had bred freely on this moor since the numbers of songbirds and voles, leading 1990, and female harrier numbers increased Figure 1 Numbers of red grouse shot on Langholm to reductions in harrier density and from two to twenty between 1992 and 1997. moor during 1975–97 in comparison with reducing their impact on grouse Peregrine numbers increased from three to numbers shot on nearby moors F and G during populations. six pairs. the same period. Grouse bags on all three moors In the short term, however, When raptor numbers were high, they fluctuated in synchrony from 1975 to 1993. After raptor–grouse problems may require more removed 30% of breeding grouse in April 1993, grouse bags on moors F and G increased active intervention in the form of and May and harriers removed 37% of the while bags on Langholm moor continued to supplementary feeding or raptor grouse chicks between June and August. decline. Harrier and peregrine numbers on translocation. Such measures require the Most of these losses appeared to be Langholm moor increased between 1992 and 1997 cooperation of conservation and shooting additional to other mortality, and we whereas the numbers of these raptors on moors F interests. The future of raptors, grouse, the estimated that they reduced post-breeding and G remained low. moorland habitats they share and the rural numbers of grouse by 50%. communities they support depends upon it. Historically, grouse bags at Langholm Clearly, if bags remain low the economic Simon Thirgood have shown a six-year cycle, peaking last in cost will be considerable. Game Conservancy Trust, 1990, with 4,038 grouse shot (Fig. 1). Since Mead2 suggests that more red grouse are Newtonmore, 1990, grouse bags have declined, with 51 killed on deer fences than are taken by Inverness-shire PH20 1BE, UK birds shot in 1997. harriers, citing work in Highland Scotland4. e-mail: [email protected] In contrast, grouse bags on two nearby There are several flaws in this argument. Steve Redpath moors, with low raptor densities, having First, deer fences are uncommon in red Institute of Terrestrial Ecology, previously fluctuated in synchrony with grouse range outside the Highlands, and Banchory, Langholm moor, increased to high levels indeed on many Highland moors. For Kincardineshire AB31 4BY, UK in 1997. example, there is little fencing at Langholm e-mail: [email protected] Increased predation by raptors at and collisions account for fewer than 1% of 3 1. May, R. M. Nature 389, 330–331 (1997). Langholm was considered the most likely all recorded deaths . Second, Highland 2. Mead, C. Nature 389, 780 (1997). 5 cause for low grouse bags. Grouse studies suggest that 11% of red grouse 3. Redpath, S. M. & Thirgood, S. J. Birds of Prey and Red Grouse management at Langholm cost £99,500 deaths are due to collisions but 48% are due (HMSO, 1997). (US$168,000) in 1997 and, with grouse to raptor predation. Third, fences pose 4. Baines, D. & Summers, R. W. J. Appl. Ecol. 34, 941–948 (1997). 5. Hudson, P. J. Grouse in Space and Time (Game Conservancy Trust, shooting producing £40 per bird, a bag of fewer problems to red grouse than to 1992). 2,487 grouse was required to balance costs. woodland grouse as strikes are 6. Mead, C. The Times, 7 & 23 November 1997.

from high-latitude forests and tundra. be mutual. Again, there will always be an Exaggeration or (2) He suggests that the IPCC has not argument on the basis of equity, but we provided a study of the effects on the global have never previously allowed such underestimate? economy of restricting the use of fossil arguments to prevent major transitions in Sir — John Maddox urged caution in fuels. He is correct, but there are ample human affairs. approaching the Kyoto conference on studies to show that the transition can be The Kyoto meeting has been dealing climate change for three reasons (Nature made with great advantage. I suggest with with the most important social and 390, 111; 1997). In each of these reasons he he consults a recent study by the World political issue of our time. It is essential that is seriously mistaken. Resources Institute led by Dr Robert systematic and rapid progress be made (1) He suggests that the predictions of Repetto. towards stabilizing, not the emissions, but the Intergovernmental Panel on Climate (3) He suggests that the problem of the atmospheric burden of heat-trapping Change (IPCC) may exaggerate the rate of inequity between rich and poor countries gases. The cost of failure is progressive change by a factor of two. The fact is that has not been resolved. The issue will never environmental impoverishment and they may underestimate the rate of change be resolved to the satisfaction of all, but political chaos. by a factor of two. The potential for an there is good basis for believing that the George M. Woodwell underestimation seems especially great less-developed world can leap over the (Director) because of the uncertainties of biotic fossil-fuel age into an era of far more Woods Hole Research Center, responses, especially the possibility of efficient use of energy with reliance on 13 Church Street, PO Box 296, releasing large quantities of additional enduring sources. The developed world can Woods Hole, carbon as carbon dioxide and methane and should aid this transition.The gains will Massachusetts 02543, USA