Abstract
The origin of vocal learning in animals has long been the subject of debate, but progress has been limited by uncertainty regarding the distribution of learning mechanisms across the tree of life, even for model systems such as birdsong. In particular, the importance of learning is well known in oscine songbirds, but disputed in suboscines. Members of this diverse group (∼1150 species) are generally assumed not to learn their songs, but empirical evidence is scarce, with previous studies restricted to the bronchophone (non-tracheophone) clade. Here, we conduct the first experimental study of song development in a tracheophone suboscine bird by rearing spotted antbird (Hylophylax naevioides) chicks in soundproofed aviaries. Individuals were raised either in silence with no tutor or exposed to standardized playback of a heterospecific tutor. All individuals surviving to maturity took a minimum of 79 days to produce a crystallized version of adult song, which in all cases was indistinguishable from wild song types of their own species. These first insights into song development in tracheophone suboscines suggest that adult songs are innate rather than learnt. Given that empirical evidence for song learning in suboscines is restricted to polygamous and lek-mating species, whereas tracheophone suboscines are mainly monogamous with long-term social bonds, our results are consistent with the view that sexual selection promotes song learning in birds.
Highlights
Vocal learning – the encoding and production of acoustic traits acquired from conspecific or heterospecific tutors – is restricted to very few groups of birds and mammals, and understanding its origins remains a core aim of evolutionary biology [1,2]
Because we found no significant difference in the structure of male and female H. naevioides songs as described by all three principal components (PC) (Table 2), we pooled song data from the sexes for this analysis
We have shown that H. naevioides individuals raised in captivity under experimental conditions produced crystallized adult songs that were statistically indistinguishable from those produced by wild adults
Summary
Vocal learning – the encoding and production of acoustic traits acquired from conspecific or heterospecific tutors – is restricted to very few groups of birds and mammals, and understanding its origins remains a core aim of evolutionary biology [1,2]. It is often assumed that songs develop without learning from tutor birds in the suboscines, a diverse clade of passerines containing ,1150 species. The finding that parrots are the sister group to both clades of passerines, the oscines and suboscines [3,4], has cast some doubt on whether suboscines develop songs by learning or not [2,5,6]. Recent evidence that vocal learning occurs in some species of suboscine suggests that they offer a better system for understanding the origins of this trait than do oscines and parrots, wherein learning is virtually universal
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