「Nature via nurture of vocal learning in hybrid songbird」

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Kazuhiro Wada, Faculty of Science, Hokkaido University

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Abstract 

Both  “nature”  and  “nurture”  influence  the  learning  process.  Like  human  speaking, birdsong  is  a  learned  vocalization  regulated  by  genetic  and  environmental  factors. Songbird juveniles develop their songs, which are species-specifically constrained but individually unique, through the critical period of vocal learning. However, how genetic and  environmental  instructions  modulate  the  vocal  learning  process  is  not  well understood. To elucidate this, we examined song development of hybrid songbirds, whose parental species sing different species-specific songs. Hybrid songbirds exhibit a wide variability  of  individual  differences  of  acquired  song  features  under  song  playback tutoring environments. When the juveniles had experience hearing both parental species songs, approximately half population of hybrid birds acquired intermediated patterns of both parental species. In contrast, the other population of hybrid birds selectively acquired either one of parental species songs. The individual variability of song in hybrid birds was emerged  as  biased  phonological  features  from  the  initiation  of  song  production. Intriguingly, even under single-species song tutoring, some population of hybrid birds persistently developed songs with non-tutored parental species features, suggesting the predisposition of vocal learnability. In parallel, the average of song features was different between tutoring groups of the pupils, indicating that the educational effect of tutored song types additionally contributes to the learning process of song pattern. The trend of predisposed learnability of song were differently biased among breeding families. These results demonstrate “nature via nurture” associated with the development of individual uniqueness of vocal learning processes.