Letter: Magpies found not guilty

Sir: The British Trust for Ornithology has not failed to address the possible link between the decline of many familiar songbirds and the increase in magpie numbers (Letters, 19 April). Our data, based on the work of tens of thousands of birdwatchers over many years, provide more detailed information than just the gross population trends.

We use our data both to investigate various potential causes of reductions in bird numbers and to focus more detailed studies on the most likely of them. So far, the evidence is that magpies, while they may affect the numbers of some other species on a local scale, are not responsible for the observed widespread declines of many other species. In contrast, there is extensive evidence that many species have been adversely affected by developments in farming practices.

Modern farming appears to represent the greatest threat to birds in Western Europe today. This is a problem for society at large, which determines the policies and economic conditions under which farmers operate. Finding a solution will not be easy and will not be helped by blaming everything on one factor, be it magpies or anything else.

Should our work ever suggest that magpies are, indeed, responsible for reducing the populations of other birds, then we shall draw that conclusion clearly to the attention of those responsible for wildlife policy. It is not for BTO to campaign for culls but to urge that the management of the countryside is based on sound evidence, not prejudice.

JEREMY J D GREENWOOD

British Trust for Ornithology

Thetford, Norfolk