Learning plays a part in the development of song in all the songbirds (oscines) studied to date, yet its functional significance is poorly understood. Our studies of zebra finches have concentrated on the timing of song learninq and on why birds choose one tutor rather than another. Exposed to a series of tutors young males learn their song from one they encounter between independence from their parents and sexual maturity (35-65 days). Lack of contact with a singing male at that stage may lead to a delay of learning or to recall of the father's song heard earlier. They tend also to choose a tutor who sings and looks like the father, and one with which they interact, particularly aggressively. While they will not normally learn from individuals that they cannot see, or from tape recordings, the major factor here appears to be the lack of interaction between tutor and tutee in such circumstances. Females may also influence tutor choice: we have some evidence that males exposed to two songs develop that preferred by the females with which they are housed. As song in this species is primarily sexual in function, such a mechanism would appear highly advantageous to young males competing for mates.