PHOTOPERIOD AND TUTOR ACCESS AFFECT THE PROCESS OF VOCAL LEARNING

Song-learning in white-crowned sparrows, Zonotrichia leucophrys, invol ves three steps: memorization of external models, song practice and se lection of a song from the practiced repertoire for crystallization. T hese three events occur in a sequential and predictable order during t he first year of life in captive sparrows. To study the external regul ation of these events, we raised nestling sparrows under conditions in which photoperiod and tutor exposure were manipulated. We measured pl asma testosterone concentration twice a month to-study its role in the mediation of vocal learning. We conclude that the timing of song memo rization is relatively impervious to photoperiodic manipulation. Song practice and crystallization, however, were readily influenced by both photoperiod and tutor exposure. We suggest that low testosterone conc entrations permit acquisition at an older age than would normally occu r, and confirm that testosterone propels the transition to production- of crystallized song, but is not required for the onset of song practi ce. (C) 1998 The Association for the Study of Animal Behaviour.