A COMPARATIVE APPROACH TO VOCAL LEARNING - INTRASPECIFIC VARIATION INTHE LEARNING-PROCESS

Vocal learning in birds often results in geographically distinct 'dial ects'. To examine whether genetic variation underlies intraspecific di fferences in vocal development, young male white-crowned sparrows from sedentary (Zonotrichia leucophrys nuttalli) and migratory (Z. I. oria ntha) populations were reared in standardized conditions in the labora tory, and tutored throughout the first year of life with a changing ro ster of tutor songs. Male nuttalli acquired their tutor imitations at a later age, and over a broader range of ages, than did oriantha males . All males eventually crystallized a single song type, but male orian tha sang imitations of more tutor songs in plastic song, and persisted in plastic song twice as long as nuttalli males. Nuttalli imitations of tutor songs were fragmentary, but their imitations of specific syll ables were more accurate than those of oriantha. These genetically bas ed differences in vocal learning may be different strategies to achiev e song matching with territory neighbours in migratory and sedentary p opulations. Young migratory oriantha face a shorter singing season dur ing the early sensitive phase for song acquisition and greater uncerta inty over where they will breed as yearlings relative to nuttalli male s, who may occupy territories relatively closer to their birthplace, a nd may settle as early as their first autumn. Male oriantha acquire se veral song dialects when young, and then, through a process of selecti ve attrition, retain the song that matches the local dialect where the y settle to breed. In contrast, nuttalli may retain the ability to acq uire an accurate song copy from a neighbour when they establish a terr itory. (C) 1995 The Association for the Study of Animal Behaviour