Bush, bugs, and birds; interdependency in a farming landscape

Abstract

Changes in farming practices over the second half of the twentieth century greatly reduced the extent of natural areas remaining within agricultural landscapes. Field margins and hedgerows have recently been recognized as important habitat in maintaining wildlife diversity and proper ecosystem functioning. Ecotones, defined as the transitionary area of vegetation between woody plant species and the arable crop, are an especially important landscape element for birds and arthropods. In this manuscript, we aimed to evaluate which hedgerow attribute was best at predicting avian densities in a conventional and organic farming landscape. Furthermore, we wished to investigate if these same hedgerow attributes could explain arthropod family density, richness and diversity, and how these were correlated to avian densities. An information theory-based multimodel inference method was used to identify which factors influenced variability in avian densities. Although not always significant, avian densities increased with arthropod richness at our study sites. Ecotone width is the best predictor of avian densities and arthropod richness while percent gap is the most important factor if a manager wishes to increase avian diversity (H’) in hedgerow habitats. Increasing ecotone width benefits both avian densities and arthropod richness that in turn further increases bird numbers in our farming landscape.