Female song rates in response to simulated intruder are positively related to reproductive success

Kristal E Cain,Naomi E Langmore,Andrew Cockburn

doi:10.3389/fevo.2015.00119

Kristal E Cain, Naomi E Langmore + Show 1 more

Open Access

https://doi.org/10.3389/fevo.2015.00119

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Abstract

Bird song is well studied in males as a sexually selected behavior. However, although song is also common among females, it is infrequently examined and poorly understood. Research suggests that song is often used as a resource defense behavior and is important in female-female competition for limited resources, e.g. mates and territories. If so, song should be positively related to fitness and related to other resource defense behaviors, but this possibility has rarely been explored. Here we examine fitness estimates in relation to spontaneous song rates and song rates in response to a simulated intruder (playback), in the superb fairy-wren (Malurus cyaneus), a cooperatively breeding songbird. We also determine how song rates relate to other territorial defense behaviors. Song rate in response to playback, but not spontaneous song rate, was positively related to nest success and the number of fledglings produced by successful females. Further, response song rate was also correlated with other territorial defense behaviors (latency to respond and flights). This evidence supports the hypothesis that female song may be used in the context of female-female competition to improve access to limited reproductive resources, and suggests that song may provide direct fitness benefits.

Highlights

Territorial song is a classic example of a sexually selected trait in males, and usually functions in the contexts of male-male competition and female mate choice (Catchpole and Slater, 1995)
To test the hypothesis that song rate is important in territory defense and has important consequences for female fitness we examined the relationship between reproductive success and song in two contexts: spontaneous song rates and song in response to a simulated female intruder
The total number of fledglings produced across the breeding season was positively related to response song rate, it was not statistically significant (Figure 3, Table 2)

Summary

Introduction

Territorial song is a classic example of a sexually selected trait in males, and usually functions in the contexts of male-male competition and female mate choice (Catchpole and Slater, 1995). Females may be territorial, and recent comparative work has shown that female song is both phylogenetically widespread and ancestral, suggesting that song may serve critical functions in females (Price, 2009; Odom et al, 2014). Researchers have argued that female song may be an important signal used by females in intrasexual competition when critical resources are limited (e.g., social partners or territories; Langmore, 1998; Price et al, 2009; Odom et al, 2014). Variation in the expression of song should be positively related to resource acquisition and fitness. If song is used in competitive scenarios, it should be positively associated with other defense behaviors, e.g., attacks. There are scant data addressing these possibilities (Eens and Pinxten, 1998; Langmore, 1998; Illes and Yunes-Jimenez, 2009; Illes, 2014)

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