Nest predation decreases with increasing nest height in forest songbirds: a comparative study

Nest predation is the most important factor responsible for nest failure in birds. Nest height may be a factor that affects the rate of nest depredation in different species. In this comparative study, we tested a relationship between nest height and nest depredation in open nesting songbirds. We analyzed data from 357 populations of 252 species and found that nests built high in trees were safer than those closer to the ground. Nest depredation rates strongly decreased with increasing nest height above 5 m. This could be because there are fewer nest predator species foraging in the canopy or because there is a lower density of nesting birds making it less profitable for predators to search for nests there. We also found that ground nests in open habitats were more likely to be depredated than those in shrublands and forests. This may be because open habitats are less complex and thus more easily searched by nest predators, or because most nests in open habitats are ground nests and predators can focus on them without having to search other vegetation layers.