Intergradation of Song between Two Subspecies of White-Crowned Sparrows on the West Coast of North America

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Abstract
Previous studies showed that two subspecies of White-crowned Sparrow Zonotrichia leucophrys intergrade in morphological, physiological, and electrophoretic traits along the north coast of California, U.S.A. Characteristics of song, however, did not exhibit variation concordant with that of the other traits. Songs intermediate between those of Z. l. nuttalli and Z. l. pugetensis occurred from approximately the northern end of morphological intergrade, at Clam Beach, California, north to about the coastal redwood forest. At Crescent City, California, just north of the redwoods, features of the song shifted more toward those of Z. l. pugetensis, and all birds recorded from here north of Blanchard (1942) suggested a gradual transition in migratory behavior from non-migratory Z. l. nuttalli to fully migratory Z. l. pugetensis over approximately the same zone that the songs seem to intergrade.