Relative effects of arable land-use, farming system and agri-environment schemes on landscape-scale farmland bird assemblages

Context Farmland biodiversity has been declining because of agricultural intensification and landscape simplification. Many farmland birds breeding in non-crop habitats use arable land as their feeding habitat (and vice versa) and understanding habitat composition and configuration at the landscape scale is important for their conservation.Objectives We explored the relationship between farmland bird densities and land-use characteristics at a landscape-scale (mean size 235 ha) to reveal the most important land-use elements driving avian farmland abundance.Methods We used bird territory mapping from 36 study landscapes across Finland to study relationships between densities of total farmland birds, open field species, edge species, farmyard species, and Farmland Bird Indicator (FBI) species, and multiple descriptors of the composition and configuration of the study landscape mosaics, reflecting the full range of available crop types, farmland structures, non-crop habitat types, and soil type.Results Densities of farmland birds increased with greater areas of leys and pastures, subsidized grasslands, habitat diversity, and farmyards with animals, and those effects were consistently stronger compared to effects of non-crop habitats. Positive effects of the relative area of leys and pastures in the landscape was most often consistent in the species-specific models, whereas species-level responses to other landscape characteristics were idiosyncratic, reflecting the variety of the species' ecologies and habitat requirements.Conclusions We demonstrate that overall habitat diversity, and habitat elements like subsidized grasslands, pastures, and farmsteads with animal production support higher bird diversity at the level of landscape mosaics. Our results suggest that studies based on field-scale study units need to be complemented with landscape-scale studies to reveal a holistic understanding of land-use intervention impacts on farmland birds.