Influence of landscape scale on farmland birds breeding in semi-natural pastures

Little attention has been paid to fragmentation effects on organisms living in open habitats in which species may have high mobility and generalized habitat use. We investigated landscape effects on 23 farmland bird species breeding in 72 semi-natural dry pastures distributed equally among three landscape types (agricultural-dominated, mosaic, and forest-dominated) in southcentral Sweden. There were generally higher local abundances of farmland birds in pastures located in agricultural-dominated and mosaic landscapes than in forest-dominated landscapes. Species feeding on a mixed diet as well as resident species and temperate migrants were most numerous in pastures located in agricultural-dominated landscapes and least numerous in forest-dominated landscapes. While controlling for the effects of local pasture area and vegetation structure, we found that the local abundance of 18 (78%) farmland bird species was significantly associated with the composition and structure of the surrounding landscape. The landscape distance that explained the largest part of local variation in abundance varied among species according to the size of their breeding territories or foraging home ranges. Our results suggest that habitat use of farmland birds breeding in pastures is affected both by suitable foraging habitats in the surrounding landscape and by nest sites within local pastures. Despite the generally higher abundances of farmland birds in pastures located in agricultural-dominated landscapes, most species of European and Swedish conservation concern had higher abundance in pastures located in more forested landscapes. Thus, the rapid loss of semi-natural dry pastures in forest-dominated landscapes is a serious threat to the future of these species in Sweden.