Geographical Variation in Song and Song Dialects of Montane White-Crowned Sparrows

We sampled the songs of 18 populations of montane Whitecrowned Sparrows (Zonotrichia leucophrys oriantha)in order to define their dialect groups, if any, and to explore vocal affinities with other western subspecies of Z. leucophrys. We found a clear-cut regional differentiation of song primarily on the basis of syllabic morphology and secondarily on the sequence of elements in the song. The birds of the Sierra Nevada and the San Bernardino Mountains of California constitute a fairly homogeneous dialect group related to another distinct group in the Warner Mountains, California, which are separated from the Sierra Nevada to the north by habitat unsuited to breeding oriantha. Those in two nearby but isolated desert ranges share a unique song type resembling that of Z. l. gambelii. Oriantha in the Wallowa Mountains, Oregon, to the northeast of the Steens Mountains, are allied with the dialect region of the northern Rocky Mountains. Syllabic morphology and the sequence of song elements also suggest certain vocal affinities of oriantha with other western subspecies of Z. leucophrys. For instance, the songs of oriantha in the Sierra Nevada, Warner Mountains, and San Bernardino Mountains have elements in common with those of nuttalli in central California and pugetensis north of the Columbia River. The songs of oriantha at Hart Mountain and in the Steens Mountains are very similar to those of gambelii in Alaska and the western Canadian Rockies. The songs of oriantha in the San Bernardino Mountains (a population founded after 1907)are identical with those of the central Sierra Nevada, and thus trace the origin of the founding group. We postulate that these and other data are consistent with Rand's interpretation of the subspecific differentiation of these sparrows in Pleistocene refugia.