Captive rearing experiments confirm song development without learning in a tracheophone suboscine bird

Area of Science:

• Ethology
• Bioacoustics
• Evolutionary Biology

Background:

• Vocal learning mechanisms in animals, particularly birdsong, remain incompletely understood.
• The role of song learning is established in oscine songbirds but debated in suboscines, with limited empirical data.
• Previous research on suboscine song development was confined to the bronchophone (non-tracheophone) clade.

Purpose of the Study:

• To investigate the song development of a tracheophone suboscine bird, the spotted antbird (Hylophylax naevioides).
• To experimentally determine whether spotted antbird songs are innate or learned.
• To contribute to understanding the evolutionary patterns of vocal learning across avian taxa.

Main Methods:

• Rearing spotted antbird chicks in soundproof aviaries under controlled conditions.
• Exposing chicks to either silence (no tutor) or a heterospecific tutor's song via standardized playback.
• Monitoring song development and crystallization over time until maturity.

Main Results:

• Spotted antbirds required a minimum of 79 days to produce a crystallized adult song.
• The developed songs were indistinguishable from wild conspecific song types.
• No evidence of song learning was observed in either the silence-reared or tutor-exposed groups.

Conclusions:

• The findings suggest that adult songs in tracheophone suboscines, like the spotted antbird, are innate rather than learned.
• This contrasts with song learning observed in some other suboscine groups, particularly polygamous and lek-mating species.
• The results support the hypothesis that social mating systems and sexual selection may influence the evolution of vocal learning in birds.