A comparison of winter bird communities in agricultural grassland and cereal habitats in Ireland: implications for Common Agricultural Policy reform

Capsule. In winter, grassland sites had greater bird numbers compared to winter cereals, but a number of species of conservation concern were exclusively recorded on winter cereals. Aims. To compare the winter bird communities in grassland and winter cereal fields. Methods. Grassland and winter cereal fields were surveyed for overwintering birds in a landscape of mixed grassland and arable agriculture. Results. Generalized Linear Models demonstrated that total bird abundance, the mean abundance of the majority of ecological groups and that of several common species, were significantly greater in grassland compared with winter cereal fields. However, a number of species of conservation concern, e.g. Skylark Aluda arvensis, were observed only on winter cereal fields. Only a minority of bird variables showed a positive response to field size. Of these, total bird species richness and the Shannon and Simpson's diversity indices showed positive significant responses to increasing field size, which may alternatively and perhaps more correctly be interpreted as a positive response to field boundary density within the farmed landscape. Conclusions. Farmland habitats are important for the provision of overwintering resources for birds, and policy directed towards bird conservation should target the management of locally significant habitat types. The implications of these findings are discussed in light of the proposed revision of the Common Agricultural Policy in 2014, particularly the proposed measure for crop diversification.