Cultural and Genetic Differentiation of Two Subspecies of White-Crowned Sparrow

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Abstract
Geographic variation in song, a learned characteristic of white-crowned Sparrows (Z. leucophrys), was compared to variation in morphological, physiological and allozyme traits across an intergrade between 2 sspp. Along the north coast of California [USA], the song structure typical of the southern Z. l. nuttalli extended throughout the entire intergrade zones of the other characters. Not until reaching the extreme north end of the intergrade with the northern distributed Z. l. pugetensis were any Z. l. pugetensis song characteristics encountered. It is at the north end of the intergrade that the birds become migratory (Blanchard 1942) and other workers have identified this as the clear demarcation between subspecies. One possible theory is that if the subspecies met in secondary contact near what is now a fairly abrupt transition between migratory and non-migratory behavior, and this contact was established after the last glacial period, then little erosion has occurred in the cultural transmission of song over many generations. Over the same time scale, however, gene flow has occurred at least 100 km to the south and perhaps farther.