Noise-induced vocal plasticity in urban white-crowned sparrows does not involve adjustment of trill performance components

Katherine E Gentry,David A Luther

doi:10.1038/s41598-018-36276-5

Abstract

Background noise can interfere with acoustic communication and subsequently influence signaling behavior. Immediate signaling flexibility (ISF) is a context-dependent form of behavioral plasticity that allows animals to temporarily change their acoustic behavior in response to noise fluctuations and potentially improve the chances of successful communication in noisy environments. The adaptive value of ISF is ultimately contingent on the response of the intended receiver, and there are differential effects on receiver response depending on which signal component is modified. However, there is scant research on whether ISF involves modification of a signal component specifically linked to mate attraction or territory defense. Our study addresses this knowledge gap and provides important insight into whether males employ short-term signal modification in a manner that could affect mate pairing success in birds. Specifically, we explore the maladaptive potential of ISF in the San Francisco, California population of Zonotrichia leucophrys nuttalli by testing for changes in trill bandwidth and rate—the specific trill structure components known to influence the receiver’s perception of vocal performance in this species—before and during noise broadcast experiments. Although Zonotrichia leucophrys nuttalli are capable of ISF, we found no evidence that noise induces temporary adjustment of the trill structure traits used by receivers to assess vocal performance.

Highlights

Background noise can interfere with acoustic communication and subsequently influence signaling behavior and the evolution of acoustic communication[1]
The link between signal modification and receiver response is explained by the fact that (1) song functions in mate attraction and territory defense and (2) song is used by receivers to assess signaler quality[24,25]
We found that urban NWCS did not adjust trill bandwidth or trill rate in response to experimental, low frequency noise broadcasts

Summary

Introduction

Background noise can interfere with acoustic communication and subsequently influence signaling behavior and the evolution of acoustic communication[1]. Until there is sufficient evidence that ISF occurs in a song component that influences a signalers’ ability to defend his territory or attract mates, we can only continue to speculate about the effect that ISF has on vocal performance Addressing this knowledge gap will provide important insight into whether short-term signal modification has implications for territory defense or mate pairing success. The NWCS sings a single stereotyped song type, comprised of introductory, complex note, and terminal trill components (Fig. 1), and experimental evidence confirms: (1) both trill bandwidth and trill rate are important during male-to-male territorial interactions, (2) male receivers use each trill trait when assessing vocal performance of competitors, and (3) the strength of receivers’ response is not influenced by the background noise level of their territory[27,35,36]. ISF could negatively affect the receiver’s perception of vocal performance if it involves signal modification that reduces trill bandwidth or trill rate

Methods

Results

Conclusion