Predator-induced stress changes parental feeding behavior in pied flycatchers

Abstract

Many vertebrate species alter their reproductive behavior under stressful conditions. Available evidence in wild birds suggests that under food limitation, parents reduce overall provisioning rate while increasing selectivity of food distribution within brood in favor of senior siblings. However, how acute stressors such as predation risk influence the magnitude and direction of changes in parental provisioning is poorly understood. In this study, a small passerine bird, the pied flycatcher (Ficedula hypoleuca), was used as a model species to investigate parental provisioning strategies when exposed to different types of predators. Parents reduced provisioning rates remarkably when exposed to a predator of adults, whereas no behavioral change was observed when nest predation was imitated. Under normal conditions, parents preferred senior chicks to juniors. In contrast to experiments with food limitation, parents allocated food equally to senior and junior siblings under predation risk, irrespective of the type of a predator. No sex-related differences in parental provisioning strategies were found. We conclude that parents alter several aspects of their behavior in response to fear stress. If danger to parents occurs repeatedly, temporal reductions in provisioning rates may have cumulative and potentially harmful consequences on offspring performance.