We investigated local and regional singing patterns of Nashville Warblers (Oreothlypis ruficapilla) in southern Oregon. Each male employed a single song, but within local populations individuals sang diverse and distinct variants with a mean of 13.5 ± 1.5 (±SD) variants among 20 males sampled at each of 10 sites. Forty-one variants were recorded among the 200 males, and 17 variants were shared among two or more sites separated from 2–92 km. The mean number of variants shared between pairs of sites was high (7.9 ± 1.6) and did not vary with distance separating them. Neighboring individuals showed no tendency to sing the same variant. The resulting pattern at each site was a mosaic of diverse variants drawn from a restricted pool of variants. Several of the variants recorded in southern Oregon were also recorded >400 km north in incidental sampling, indicating a broad distribution of the variants. High local song diversity implies that an important function of song is to proclaim the identity of the individual. Possible mechanisms for maintenance of high local song diversity are discussed.