OVERPRODUCTION IN SONG DEVELOPMENT - AN EVOLUTIONARY CORRELATE WITH MIGRATION

Many songbirds overproduce songs during development and shrink the rep ertoire at the time of adult crystallization. The amount of overproduc tion varies between species. The hypothesis was tested that overproduc tion of learned songs during ontogeny is correlated with a migratory a nnual cycle. It is argued that in migrants, overproduction permits son g matching between territory neighbours when song memorization is rest ricted to an early sensitive phase and young males subsequently disper se relatively long distances to their first breeding territory. Song d evelopment was compared in the sedentary Nuttall's white-crowned sparr ow, Zonotrichia leucophrys nuttalli, and two migratory taxa, the Puget Sound white-crowned sparrow, Z. l.pugetensis, and the mountain white- crowned sparrow, Z. l.oriantha. Although the Puget Sound and Nuttall's white-crowned sparrows are sister taxa, male Puget Sound sparrows mor e closely resembled the more distantly related, but migratory, mountai n white-crowned sparrow on every measure of song development studied. It is concluded that a migratory annual cycle is a better explanation of diversity in vocal development in this species than recency of comm on ancestry. (C) 1996 The Association for the Study of Animal Behaviou r.