Changes in Song Dialect Distributions and Microgeographic Variation in Song of White-Crowned Sparrows (Zonotrichia leucophrys nuttalli)

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Abstract
Multivariate analysis and analysis for spatial autocorrelation of 21 frequency and time characteristics of the songs of White-crowned Sparrows (Zonotrichia leucophrys nuttalli) showed that within a dialect area the songs of neighboring males were no more similar to one another than to the songs of non-neighbors. This result refutes one prediction of the hypothesis that song dialects are maintained because males copy the songs of neighbors to gain an advantage in territorial defense or mate attraction. Historical events were important in producing changes over 10 yr in dialect distributions in an area of secondary contact between two dialects. The dialect distributions changed as the sparrow population invaded a new area where the vegetation had been modified, and the sparrows disappeared from a drought-affected area. The basic structure of the dialects did not change in 18 yr, and the fine structure, measured by 21 variables, did not differ between the 2 yr sampled. In 10 yr the two dialects did not blend to form an intermediate dialect.

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