Sparrows learn adult song and more from memory.

Male swamp sparrows reared in the laboratory and exposed to taped songs during infancy produce accurate imitations of the material following an 8-month interval with no rehearsal. When the first rehearsal occurs, at about 300 days of age, large numbers of syllables are perfected. They are developed through invention and improvisation as well as imitation. Most are discarded at the time of song crystallization. Hence, these songbirds learn more than they manifest in full adult song.