Voices in the dark: predation risk by owls influences dusk singing in a diurnal passerine
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Predation is an important cost of communication in animals and thus a potent selection pressure on the evolution of signaling behavior. Heterospecific eavesdropping by predators may increase the vulnerability of vocalizing prey, particularly during low light, such as at dusk when nocturnal predators are actively hunting. Despite the risk it entails, dawn and dusk chorusing is common in passerines. However, the dusk chorus has not been studied much, neglecting the opportunity for understanding how eavesdropping between predators and prey may shape communication in birds. Here, we report the first demonstration of simulated predation risk (playback of owl vocalizations) altering the dusk chorus of a diurnal passerine, the veery (Catharus fuscescens). Veeries have a pronounced dusk chorus, singing well after sunset and potentially exposing themselves to predation by owls. In response to brief playbacks of owl calls (~30 s of calls presented three times over 25 min), veeries sang fewer songs post-sunset and stopped singing earlier relative to control trials. These changes in singing remained evident 30 min after the last owl stimulus. Although the avian dusk chorus has received relatively little attention to date, our results suggest that the dusk chorus may pose a higher predation risk to singing males that may influence the evolution of singing behavior in diurnal birds.
KeywordsAnimal communication Dusk chorus Heterospecific eavesdropping Predation risk Veery
The authors thank Stacy Tekstar, Angela Olsen, and Claire Randall for patiently and meticulously identifying all of the veery songs throughout these long recordings, and Janice Kelly for additional support in the field. Two anonymous reviewers provided constructive comments to an earlier draft of the manuscript. This research was supported in part by a grant to KAS from the National Science Foundation (DEB 0746985).
Our study was conducted in compliance with the ethical standards of animal care and use at Texas Tech University and the United States of America.
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