Two novel vocalizations are used by veeries (Catharus fuscescens) during agonistic interactions.

Kara L Belinsky,Kenneth A Schmidt,Claire E Nemes,Johan J Bolhuis

doi:10.1371/journal.pone.0120933

Kara L Belinsky, Kenneth A Schmidt + Show 2 more

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https://doi.org/10.1371/journal.pone.0120933

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Abstract

Avian vocalizations are common examples of the complex signals used by animals to negotiate during agonistic interactions. In this study, we used two playback experiments to identify agonistic signals in a songbird species with several acoustically complex songs and calls, the veery. In the first experiment, we compared veery singing behavior in response to simulated territorial intrusions including playback of three variations of veery song: 1) song alone as a control, 2) songs with added whisper calls, and 3) songs with introductory notes removed. In the second experiment, we used multimodal stimuli including songs, whisper calls and songs with introductory notes removed, along with a robotic veery mount. Focal males readily responded to all of the playback stimuli, approached the speaker and/or robotic mount, and vocalized. Male veeries gave more whisper calls, and sang more songs without the introductory note in response to all types of playback. However, veeries responded similarly to all types of stimuli presented, and they failed to physically attack the robotic mount. These results indicate that rival veeries use two different types of novel vocalizations: whisper calls and songs lacking the introductory note as agonistic signals, but do not allow us to discern the specific functions of these two vocalizations.

Highlights

Vocalizations are commonly observed examples of agonistic signals that animals use during conflicts over resources [1]
We used two playback experiments to identify agonistic signals in the veery. We identified those vocalizations that are used by the focal male in an aggressive context, and compared them to vocalizations used in response to two types of putative agonistic signals
We find these results to be convincing evidence that whisper calls and songs without introductory notes are agonistic signals in this species

Summary

Introduction

Vocalizations are commonly observed examples of agonistic signals that animals use during conflicts over resources [1]. Agonistic signals allow competitors to assess each other’s relative fighting motivation or ability, and to avoid costly physical contests when one competitor chooses to retreat rather than fight [2]. The vocalizations of red deer, Cervus elaphus [3], and common toads, Bufo bufo [4], signal body size, which is a good indicator of fighting ability in these species. The vocalizations of songbirds are a fruitful model for studying agonistic signaling because these birds have complex vocal repertoires, often including a variety of learned songs and largely innate calls that are often used to signal aggressive intent.

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