Rudimentary substrates for vocal learning in a suboscine.

Vocal learning has evolved in only a few groups of mammals and birds. The key neuroanatomical and behavioural links bridging vocal learners and non-learners are still unknown. Here we show that a non-vocal-learning suboscine, the eastern phoebe, expresses neural and behavioural substrates that are associated with vocal learning in closely related oscine songbirds. In phoebes, a specialized forebrain region in the intermediate arcopallium seems homologous to the oscine song nucleus RA (robust nucleus of arcopallium) by its neural connections, expression of glutamate receptors and singing-dependent immediate-early gene expression. Lesion of this RA-like region induces subtle but consistent song changes. Moreover, the unlearned phoebe song unexpectedly develops through a protracted ontogeny. These features provide the first evidence of forebrain vocal-motor control in suboscines, which has not been encountered in other avian non-vocal-learners, and offer a potential configuration of brain and behaviour from which vocal learning might have evolved.