Nesting strategy predicts farmland bird response to agricultural intensity

Abstract

Large-scale studies investigating impacts of agricultural practices on biodiversity showed that farmland bird population sizes are negatively related to national agricultural intensification indices in Europe. Here, it was tested whether the nesting strategy of farmland species predicted their abundance variations along a gradient of agricultural production intensity. Ground-nesters, which are strongly declining all over Europe, were expected to be impacted more directly by production intensity than hedge-nesters which would be instead impacted by hedge loss. To test this prediction, previously unavailable fine-scale agricultural data were used over an entire country representing highly diverse farmlands. We modelled the local abundance of 43 farmland bird species, using data from the French breeding bird survey, along an index of agricultural production intensity based on standardized crop yields and herbivore stocking rates, controlling the analysis for local climate and farmed habitat type. 68% of ground-nesters had lower relative abundance in more productive farmlands, whereas only 17% of hedge-nesters did. Nesting strategy explained an important part of bird species responses to spatial variation in agricultural production intensity. Our results suggest that although hedge loss and production intensification were parts of the strong agricultural intensification in Europe, these two phenomena are impacting different bird species.