A meta-analysis of edge effects on nesting success in forest and shrubland birds of eastern North America

Abstract

Numerous studies report proximity to land cover edges decreases avian nesting success, yet variation among species, sites, and nesting guilds obscures overall patterns. Nest success is a key demographic parameter, and edges are often created from anthropogenic disturbance; therefore, further understanding of nest success and edges should inform bird conservation efforts. We performed a meta-analysis to examine effects of edges on mature forest and shrubland bird nest survival in eastern North America. Sixteen studies fit our inclusion criteria, comprising data for 11 mature forest and 9 shrubland species. Nest success for mature forest birds declined with proximity to edges. Additionally, random effects of species and study explained a relatively large amount of variance in nest survival. We did not find a significant edge effect for shrubland birds, but only two data points (averaged within studies) were greater than 100 meters from an edge. Thus, in studies we compiled, an impact of edges was only apparent for forest species that nested far from edges. An interactive effect of distance-to-edge and nest placement (low vs. higher nesting height) did not significantly influence nest survival. Single-species analyses showed a relationship between distance-to-edge and nesting success for Hermit Thrush ( Catharus guttatus ), though small sample sizes may have limited our ability to detect relationships for other species. Overall, core areas greater than 250 m from edges tend to have higher nest success for mature forest birds, information that will help managers and conservationists when maintaining habitat for both forest and shrubland bird communities.

Keywords

• border
• depredation
• ecotone
• nest predation
• review