Winter agri-environment schemes and local landscape composition influence the distribution of wintering farmland birds

Abstract

Since 1992, the European Union puts in place agri-environment schemes (AES), such as unharvested set-aside fields with winter bird crops (WBC), to counteract farmland biodiversity declines that are associated with agricultural intensification since the second half of the 20th century. These measures aim at, among other things, improving habitat quality and food availability for farmland birds throughout the year. In this study in Dry Hesbaye, an agricultural region in eastern Flanders (Belgium), we use spatial generalized linear mixed models to investigate how species richness and the observation probability of ten bird species with different food diets are associated during winter (November - March) with WBC implementation in arable crop fields and the presence of landscape elements within 50 m of these fields. Our results show that species richness and the observation probabilities of nine out of ten wintering farmland bird species under study are increased at crop fields with WBC implementation. Species richness and observation probabilities are also associated with the presence of nearby landscape elements such as hedgerows, woodland, unpaved roads, or grass margins. We conclude that unharvested set-aside fields promote local diversity and observation probabilities of most of the species under study. In addition, AES measures should be implemented after considering the aforementioned natural or seminatural nearby landscape elements, which also influence local diversity and species' observation probability.