The song does not remain the same: daily singing of adult songbirds prevents passive changes in song structure independently of auditory feedback

Abstract Many songbirds learned to produce songs through vocal practice in early life and continue to sing these songs daily throughout their lifetime. While it is well-known that adult songbirds sing as part of their mating rituals, the functions of singing behavior outside of reproductive contexts remain unclear. Here, we tested the hypothesis that adult singing outside of reproductive contexts may serve to prevent passive changes in song performance. We found that suppressing daily singing for two weeks altered the acoustic and temporal structure of song, and that the song structure substantially recovered within two weeks of free singing. These reversible song changes were not dependent on auditory feedback or the age of the birds, contrasting with the adult song plasticity that has been reported previously. These results demonstrate that adult song structure is not stable without daily singing in non-reproductive contexts, and suggest that adult songbirds maintain song performance by preventing passive song changes through the physical act of daily singing throughout their life. Such daily singing likely functions as vocal training to maintain the song production system in optimal conditions for song performance in reproductive contexts, similar to how human singers and athletes practice daily to maintain their performance.