Abstract
Birdsong has long been considered a sexually selected trait that relays honest information about male quality, and laboratory studies generally suggest that female songbirds prefer larger repertoires. However, analysis of field studies across species surprisingly revealed a weak correlation between song elaboration and reproductive success, and it remains unknown why only certain species show this correlation in nature. Taken together, these studies suggest that females in numerous species can detect and prefer larger repertoires in a laboratory setting, but larger individual repertoires correlate with reproductive success only in a subset of these species. This prompts the question: Do the species that show a stronger correlation between reproductive success and larger individual repertoires in nature have anything in common? In this study, we test whether between‐species differences in two song‐related variables—species average syllable repertoire size and adult song stability over time—can be used to predict the importance of individual song elaboration in reproductive success within a species. Our cross‐species meta‐analysis of field studies revealed that species with larger average syllable repertoire sizes exhibited a stronger correlation between individual elaboration and reproductive success than species with smaller syllable repertoires. Song stability versus plasticity in adulthood provided little predictive power on its own, suggesting that the putative correlation between repertoire size and age in open‐ended learners does not explain the association between song elaboration and reproductive success.
Highlights
Birdsong is among the most elaborate forms of vocal communica‐ tion in nature
Analysis of available field data has not provided significant evidence for a strong correlation between reproductive success and song elaboration in na‐ ture (Byers & Kroodsma, 2009; Soma & Garamszegi, 2011), implying that sexual selection for more elaborate songs might only occur in a subset of species
There has been a long‐standing controversy over the putative link between birdsong elaboration, especially individual male repertoire size, and reproductive success, with some research claiming “elaborate songs [...] are the acoustic equivalent of the peacock's tail” (Catchpole, 1987) and other research stating “it is unlikely that sexual se‐ lection for more elaborate songs is widespread among songbirds” (Byers, 2011)
Summary
Birdsong is among the most elaborate forms of vocal communica‐ tion in nature. In addition, song plays a critical role in reproduction: Songbirds that cannot sing a species‐typical song have an impaired ability to attract mates (Catchpole & Slater, 2003). Field studies that do not find a relationship between song elaboration and reproductive suc‐ cess often use territory quality as a putative explanatory variable, implying that, in certain species, environmental factors make it ad‐ vantageous for females to pick territories on which to raise young based on the abundance or stability of resources instead of mak‐ ing decisions based on the resident male's song quality (Catchpole, 1986; Hiebert, Stoddard, & Arcese, 1989) Both of the afore‐ mentioned reviews (Byers & Kroodsma, 2009; Soma & Garamszegi, 2011) proposed that song elaboration may not be under uni‐ versal selective pressure across species. (a) Byers and Kroodsma 2009 Soma and Garamszegi 2011 + search for papers past 2010 studies, 28 species (b) 10 studies: did not measure repertoire complexity or had N < 4 birds studies, 28 species measurements measurements: not enough information measurements: subsets of the same data measurements: controlled for other variables measurement: looked at rare song
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