Landscape, cropping and field boundary influences on bird abundance

Comprehensive statistical models were applied to BBS data to show that for most species, variation in abundance was best predicted by landscape structure, followed by field boundary composition and finally crop types in farmland-dominated BBS squares. This means that landscape features (such as the presence of woods, villages or the mixture of grass and arable farming) have the strongest influence on farmland bird populations. However, field boundaries and, especially, crops can be both changed more easily and have changed more over time than landscape features, and so have a key role to play in driving farmland bird population trends. This makes them realistic targets for management action, as well as potential sources of future conservation problems, although the extent of these effects will be constrained by the landscapes they are found in.

Among the specific habitat influences tested, the presence of hedges with trees, which provide nesting habitat and song-posts, was shown to positively affect populations of several species, as did high levels of landscape and cropping heterogeneity. The latter boost habitat and resource variety, and therefore the number of individuals and species that can be supported.

This study has important conservation implications because it shows the potential of different components of farmland management (such as national agri-environment schemes and the Common Agricultural Policy) to contribute to bird conservation. It also demonstrates the overriding importance of landscape structure in determining bird community composition, even within landscapes dominated by farmland.