Tree and hedgerow configurations on maize farms are key drivers of granivorous passerine bird assemblage patterns

Abstract

Granivorous birds are responsible for significant cereal crop losses to farmers worldwide. However, how cropland vegetation structural features contribute to granivorous birds’ presence and assemblage patterns remains poorly understood. This study explores how granivorous bird distribution in terms of abundance similarities, densities, species richness and encounter rates, respond to habitat configuration elements and cropping methods across non Bt-maize fields. Here we compare nine intercropped to seven monoculture farms within which influence of eight vegetation structural features and two general habitat attributes on granivorous bird’s assemblages were determined across three maize growing seasons. Bird abundance similarities were most significantly influenced by heights of hedgerows and trees. For assemblage composition, whereas bird species richness was unaffected by any habitat variable, encounter rates were higher on farms with higher hedges or tall trees. On the other hand, bird densities increased on farms with abundant large mature trees, large woodlots, high hedgerows or dominance of indigenous trees, but diminished with both overall tree density and young-tree abundance. These results suggest that keeping hedgerows low, minimizing woodlot sizes and maintaining young isolated trees across the farm, may significantly contribute to reducing granivorous bird aggregation on maize farms thus mitigating potential for maize grain losses.