Flushing, capture, and bleeding do not affect return rate of female Wood Thrushes (Hylocichla mustelina) in Delaware

Abstract

Theoretical questions and conservation concerns have prompted numerous, intensive studies of songbird nesting ecology. Such studies use several techniques (flushing, capture, and blood sampling) that have the potential to negatively affect reproduction, survival, and site fidelity. Although studies have examined the effects of those techniques on avian reproduction and survival, the effect on the return rate of breeding songbirds has not been researched. We used data from a 28-year demographic study to investigate the possible effect of those three common research practices on the return rate of female Wood Thrushes (Hylocichla mustelina). We also tested reproductive success and age as predictors of return because they have been shown to influence site fidelity. Number of successful nests in a breeding season was the variable that best predicted return the following year. None of the research practices negatively affected return rate. That pattern held even among yearlings with zero production, a group that should be the most easily disturbed. We also show that using all years of return for site-faithful birds as observations (i.e. repeated sampling) inflates the estimated return rate.