The Effect of Nest Acoustics on the Begging Calls of Nestling Tree Swallows

Abstract

Animals’ long-distance acoustic signal structure minimizes habitat-specific attenuation and distortion, but it is unknown how environmental acoustics shape the signals of dependent young, or short-range signals generally. I investigated the influence of the nest environment on nestling tree swallows’ begging calls by relating nest reverberation and resonance to nest structure; relating call features to nest reverberation, resonance and structure; and testing whether call structure reduced distortion in the home nest. Reverberation was stronger in wider cavities with intact ceilings. Nestlings used shorter calls in more reverberant cavities, and longer calls with higher middle frequency and lower minimum frequency in wider cavities with smoother walls, but did not adjust call frequency in relation to resonance. Calls originally produced in a given nest did not transmit with less distortion than calls originally produced in other nests. These findings suggest that the nest environment may shape the structure of begging calls.