Many bird species learn to sing during a short phase early in their lives known as the sensitive period (also called the critical period). During this time, young songbirds are highly receptive to learning their species-specific songs from adult tutors. Like human language acquisition, this phase is time-sensitive; if a bird doesn’t hear its species' song within this period (typically a few weeks to months, depending on the species), it may never sing properly as an adult.
New research is beginning to uncover the complex brain mechanisms underlying song learning during the sensitive period. Zebra Finches are widely used as a model species for neurobehavioral research, and they learn elaborate vocalizations during a critical period of just 90 days. In one recent study, biologists found that by switching off neurons that usually inhibit vocal learning, finches could once again learn new songs and expand their repertoires. Another research group found that exposure to a new song tutor during the sensitive period resulted in significant changes in neural activity and permanent changes to specific parts of Zebra Finch brains.