Testosterone-induced shortening of the storage phase of song development in birds interferes with vocal learning

Bird song is a complex, learned behavior. Vocal learning in sparrows involves several different processes that occur in a distinct temporal pattern over the course of the first year of life. Songs are acquired without practice during a sensitive period within the first 3 months of life and rehearsal of the acquired song does not begin until 7 or 8 months of age. The function of the storage period between song acquisition and production is not known. We set out to investigate its significance by administering testosterone, known to stimulate production of adult song, to birds at 100 days of age after song acquisition was completed but some 5 months prior to normal song onset. Most testosterone-treated birds produced abnormal songs resembling those of males raised in acoustic isolation suggesting that, in sparrows, events occurring during the storage phase play a significant role in vocal learning.