The importance of size, location and vegetation composition of perennial fallows for farmland birds

Across Europe, patches of un-cropped land (field margins, fallows etc.) have been established and managed as part of agri-environment schemes (AES) to counteract the decrease of farmland biodiversity. Various studies demonstrate a positive impact of such un-cropped land on different taxa. However, there is potential to further improve the efficiency of fallow options for farmland birds. In a long-term monitoring, 12 breeding farmland bird species and sizes of perennial fallows were recorded from 1992 to 2015 in a 6.1 km2 area in Switzerland. Furthermore, habitat composition and fallow characteristics were mapped in 2012. We calculated population trends, analysed habitat associations and revealed the impact of fallow habitat characteristics on territory density. The proportion of fallows in the study site increased from 1.4 % (1992) to 8.5 % (2012). Population trends of six out of 12 censused species increased significantly over the same time, four species showed no trend and trends of t...