Species and temporal factors affect predator-specific rates of nest predation for forest songbirds in the Midwest

Abstract

ABSTRACT. Knowledge of the relative contributions of predator species to overall rates of nest predation can improve our understanding of why predation risk varies, but the identity of predators is seldom known. We used video technology to identify nest predators of the tree-nesting Acadian Flycatcher (Empidonax virescens) and the shrub-nesting Indigo Bunting (Passerina cyanea) in forests of Missouri and southern Illinois. Raptors, snakes, and nonraptorial birds were the most frequent nest predators; rodents depredated fewer nests; and mesopredators rarely depredated nests. We tested hypotheses concerning effects of songbird species, ordinal date, nest stage, height, and age on overall and predator-specific predation rates to determine whether variation in overall predation rates was attributable to a subset of nest predators. Overall predation rates were higher for Indigo Buntings than for Acadian flycatchers, were higher during the nestling stage than during incubation, and exhibited a midseason peak. C...