Comparative Biology of Pacific Coastal White-Crowned Sparrows

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Abstract
White-crowned sparrows (Zonotrichia leucophrys) taken in June-Aug. (1960-61) from 14 breeding localities of coastal California, Oregon, Washington, and British Columbia were studied year-round in an out-door aviary at San Jose, California. Southern populations (Z. l. nuttalli) are non-migratory while northern populations (Z. l. pugetensis) are migratory. Maximum testicular growth (laporatomy) was attained in southern birds in March, middle latitude birds in April, and in northern birds in May. Prenuptial molt was extensive in birds from northern populations and absent or light in birds from southern populations. The non-migratory (southern) nuttalli showed typical but less intense "Zugunruhe" with peak in March compared to the migratory (northern) pugetensis whose, peak of "Zugunruhe" was in April. "Zugunruhe" in the nuttalli is regarded as an atavistic remnant of ancestral migratory behavior. Data suggest the 2 races are in secondary contact and that the zone of steepest variation and reduced gene flow is between Westport and Capetown on the north coast of California.