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 learn to produce songs through vocal practice in early life and continue to produce many renditions of learned songs daily throughout their lifetime. While it is well-known that adult songbirds sing as part of a mating ritual, additional functions of their singing behavior are not fully understood. Here, we demonstrate that adult singing outside the reproductive contexts functions to prevent passive changes in song performance. Using a reversible behavioral manipulation, we suppressed the daily singing behavior of adult zebra finches produced in the solo context for two weeks and examined its effect on song performance. We found that singing suppression significantly decreases the pitch of song elements and both amplitude and duration of song motifs. This suggests that adult song is not acoustically stable without singing and that adult birds maintain their song performance by daily singing. Moreover, suppression-induced changes in song structure were substantially recovered within two weeks of free singing even in deafened birds. Thus, the recovery of song performance does not necessarily require auditory feedback but rather is caused predominantly by singing behavior per se (i.e., the physical act of singing). Finally, unlike the auditory feedback-dependent song plasticity previously reported, passive song changes caused by singing suppression were not significantly dependent on age. Our findings demonstrate that adult songbirds maintain song performance by preventing passive song changes through the physical act of daily singing outside the reproductive contexts throughout life. Such daily singing presumably functions as vocal training to maintain the neural and/or muscular system for song production in optimal conditions to make the best song performance in reproductive contexts.