Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review.

摘要

This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. Corvids accounted for almost all predation on shrub nests whereas mammals were the main predators of ground nests. Nest predation risk was significantly greater for shrub than for ground nests at all distances (0, 15 and 30 m) from the forest edge. However, nest predation risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the nearest tree. Different corvid species robbed nests at different distances from the forest edge. It was concluded that the relationship between the predation risk of grassland bird nests and distance to the forest edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge zone. A review of published articles on artificialshrub and ground nest predation in the temperate zone corroborated the results of this study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (?0 m from the edge).