The bird began vocalizing during the motor learning phase.

The bird starts to vocalize during the motor learning phase, practicing until it can match the song it memorized. As the bird learns, hearing the tutor’s song over and over again is helpful— up to a point. If he hears it too many times, the imitation degrades— and the source matters. If the song is played through a loudspeaker, he can’t pick it up as easily. But hide the same loudspeaker inside a toy painted to look like a zebra finch, and his learning improves. What if the baby never hears another zebra finch’s song? Interestingly enough, it’ll sing anyway.