Female song and vocal interactions with males in a neotropical wren

Maria R. D. Rittenbach,Sandra L. Vehrencamp,Michelle L. Hall

doi:10.3389/fevo.2015.00012

Maria R. D. Rittenbach, Sandra L. Vehrencamp + Show 1 more

Open Access

https://doi.org/10.3389/fevo.2015.00012

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Abstract

Bird song is thought to function primarily in same-sex competition, mate attraction, and reproductive stimulation of a partner. However, these conclusions are based largely on studies of the song of male birds in north-temperate species. We investigate female song in a Neotropical wren, Thryophilus pleurostictus, using observations and experiments to test the function of female song. Female banded wrens sang much less often than males, their songs were shorter, and their repertoire of song types was smaller. Females did not seem to sing for same-sex competition for resources or mates: female song rate did not increase in response to simulated intrusion, and females sang in response to less than one-third of playbacks simulating territorial intrusion by either unpaired or paired females. Territorial defense is important for both survival and reproduction in species that occupy all-purpose territories year-round, but female involvement in territorial defense was limited. Females were more likely to approach simulated intruders when their partner approached more closely, and were closer to their partner during playback simulating a pair of intruders, perhaps contributing to defense jointly with their partner. Females did not appear to use song to attract males for mating: only 25% of females sang in response to playback simulating an unpaired male during the nest-building period, and they were less likely to sing shortly before laying when they were more likely to be fertile. Female song in banded wrens seemed to be used primarily for communicating with their breeding partner: female songs overlapped or began within one second of a song by their partner more often than expected by chance, and male vocal behavior changed in response to song by their partner. However, the low rate of female song in banded wrens suggests this function does not select for song elaboration, consistent with the view that same-sex competition is the main driver of female song elaboration.

Highlights

Vocal and visual ornamentation of females was traditionally considered rare, with Darwin (1871) proposing that sexual dimorphism in ornamentation was due to sexual selection acting on males, and that examples of female ornamentation were due to shared inheritance of male characteristics
COORDINATION WITH PARTNER To quantify vocal interactions and test whether female songs were closely associated with male songs by chance, because of the high song rates of males, we examined frequency histograms of response intervals and used a duty cycle approach
FEMALE SONG STRUCTURE, REPERTOIRES, AND SHARING Female songs were shorter than male songs

Summary

Introduction

Vocal and visual ornamentation of females was traditionally considered rare, with Darwin (1871) proposing that sexual dimorphism in ornamentation was due to sexual selection acting on males, and that examples of female ornamentation were due to shared inheritance of male characteristics. Selection acting on females may be as, if not more, important than selection acting on males as a cause for sexually dimorphic bird song. Despite the prevalence of female song, much less is known about all aspects of female than male song (Riebel et al, 2005), including its function in inter- and intra-sexual competition and reproductive stimulation of a partner (primary functions of song in males, Catchpole and Slater, 2008). Since the theoretical framework for understanding the evolution of song was based largely on species where female song was rare, the role of vocal interactions with a breeding partner was generally not considered. Most work on female song has been conducted in duetting species, where females often coordinate their songs with those of their partners to form joint acoustic displays (reviewed in Hall, 2004, 2009). Similarities and differences with male song, and the relative importance of female song for female–female competition, male attraction, and within-pair communication are all poorly understood

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