Distribution and abundance of birds and their habitats within the lowland farmland of Britain in winter

Abstract

Capsule: Farmland bird species occurred at low densities and were highly aggregated in a small proportion of available pastures, stubble fields and farmyards. Aim: To document the current distribution and abundance of farmland birds and their habitats within the lowland farmland of Britain in winter. Methods: Over three winters volunteer observers visited a stratified random sample of 1090 1-km squares within which they counted a suite of 30 farmland bird species and mapped agricultural habitats. Results: For individual species, less than 10% of habitat patches were occupied and densities in occupied patches were low. Several differences were apparent in patterns of relative abundance compared to the 1980s. In particular marked declines of Tree Sparrow and Corn Bunting were apparent. The national distribution of cereal stubbles was localized. A large proportion of most species was found in grassland. Positive associations at the patch scale were apparent for improved grassland by invertebrate feeders and cereal and maize stubbles and farmyards, mostly by granivores. Conclusion: Many farmland passerines are highly aggregated, even within particularly favoured field types. These results are consistent with winter food resources being highly localized and the need to create more food-rich patches if declines are to be reversed. © 2008 British Trust for Ornithology.