contrast in edge vegetation structure modifies the predation risk of natural ground nests in an agricultural landscape对比优势植被结构修改自然地面巢捕食风险的农业景观.pdf

Contrast in Edge Vegetation Structure Modifies the Predation Risk of Natural Ground Nests in an Agricultural Landscape 1 1 1,2 ¨ 1 Nicole A. Schneider *, Matthew Low , Debora Arlt , Tomas Part 1 Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden, 2 Centre for Agri-Environmental Research, School of Agriculture, Policy Development, University of Reading, Reading, United Kingdom Abstract Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge- related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depen