Habitat Use and Foraging Behavior of Eastern Bluebirds (Sialia sialis) in Relation to Winter Weather

Abstract

Abstract Population declines of songbirds following severe winters draw attention to a need to better understand behavioral responses to inclement weather. We used observations of radio-tracked Sialia sialis (Eastern Bluebird) wintering in Kentucky to examine the effects of weather on habitat use, group size, foraging behavior, and diet. Home ranges were smaller than published estimates, and consisted of more open than wooded habitat, in proportion to availability. Although habitat use appeared unchanged during inclement weather, Bluebirds increased group sizes, and shifted from insectivory to frugivory during periods of sub-freezing temperatures and snow cover. Fecal analysis confirmed the weather-driven shift of diet. Inclement winter weather likely lowers the efficiency of insectivory, leading to changes in social and foraging behaviors.