Vocal Imitation in Zebra Finches is Inversely Related to Model Abundance

A juvenile zebra finch male kept singly with its father develops a fairly complete imitation of the father's song. The imitation is less complete when other male siblings are present, possibly because an imitation commences, model abundance increases. Here, we examine the consequences of allowing more or less access to a song model. Young males heard a brief song playback when they pecked at a key, but different males were allowed to hear different numbers of playbacks per day. Using an automated procedure that scores the similarity between model and pupil songs, we discovered that forty playbacks of the song motif per day, lasting a total of 30 sec., resulted in a fairly complete imitation. More exposure led to less complete imitation. An inhibitory effect of model abundance on imitation may foster individual identity and explain the vocal diversity found in zebra finches.