The capacity for song memorization varies in populations of the same species

To compare the song learning capacity of migratory and sedentary birds, we contrasted the responses of males from two different populations of the white-crowned sparrow, Zonotrichia leucophrys, to rich and lean regimes of early tutor experience. The two regimes were designed to simulate extremes in the variety of songs that young males might experience. Males from the migratory population, Z. I. oriantha, learned significantly more tutor material, from more tutor song types, and produced more song types themselves during vocal rehearsal from a rich tutoring regime than from a lean regime. Males of the sedentary nuttalli race learned similar amounts from rich and lean regimes. We argue that a migratory annual cycle introduces greater uncertainty into where a young male will breed for the first time, and that this has favoured the capacity to memorize more songs during the early sensitive phase for song memorization in migratory populations. (C) 1996 The Association for the Study of Animal Behaviour