LEARNING BY INSTRUCTION OR SELECTION: IMPLICATIONS FOR PATTERNS OF GEOGRAPHIC VARIATION IN BIRD SONG

Experience can have both instructive and selective effects on vocal development in song birds. Learning by instruction occurs when one male imitates the song of another. Learning by selection occurs when a male chooses one or more songs to retain in his repertoire based on interaction with other individuals. These models of learning make different predictions about the degree of microgeographic variation in song present in wild populations of birds. If males are instructed by their immediate territory neighbors, then the songs of territory neighbors should be more similar than are the songs of non-neighbors. In contrast, if males select a song for retention that was learned elsewhere in the dialect, the songs of neighbors should be no more similar than are the songs of nonneighbors sampled from the same dialect. We compared the songs of males sampled in two sedentary populations and four migratory populations of four subspecies of the white-crowned sparrow, Zonotrichia leucophrys. In the two sedentary nuttalli populations, males on neighboring territories sang very similar songs, indicating that males are instructed by their territory neighbors after they disperse short distances to their breeding territories. Learning by selection during territory establishment after natal dispersal appears to predominate in the four migratory populations: the songs of territory neighbors were no more similar than were the songs of non-neighbors. We conclude that the sedentary/migratory distinction in the annual cycle determines the form of vocal learning that occurs between territory neighbors.