A meta-analysis of tropical forest edge effects on bird nest predation risk: Edge effects in avian nest predation

Numerous studies have analyzed predation risk on bird nests along forest edges, but results are inconsistent and contributing factors not well understood. Few of these studies have been carried out in tropical regions, where predator communities and responses to edges may be different. In the face of ongoing forest fragmentation, understanding factors driving predation patterns along tropical forest edges are most likely crucial. We present a formal meta-analysis on tropical forest edge effects in nest predation, advancing the method applied by Batary and Midi (2004). We performed a meta-analysis of 20 tropical nest predation studies including data on more than 5000 artificial nests. We tested for edge effects on nest predation probability in relation to distance from a forest edge and assessed effects of forest cover, matrix type, geographic location and nest parameters. Further, we analyzed our data together with 13 nest predation studies from temperate forests (Batary and Baldi, 2004) in a combined meta-analysis, summing up to evidence from almost 9000 nests. Our meta-analysis of the tropical nest predation studies did not provide evidence of a forest edge effect on nest predation probability, while the result of the combined meta-analysis suggested a higher nest predation probability along forest edges. However, heterogeneity was extreme in both analyses (I-2 = 85% and 90.1%), indicating that each study, with its unique characteristics, may result in varying nest predation patterns. Landscape context, here: forest cover, appeared to modulate nest predation risk in relation to edge distance. Conservation managers should be aware that a standard formula for conservation actions might be of little help, since edge effects seem to vary with study site settings and landscape context. We further point out that standardized reporting guidelines for primary research might help to interpret high variation in field data. (C) 2012 Elsevier Ltd. All rights reserved.