LONG-TERM CHANGES IN SONGS AND SONG DIALECT BOUNDARIES OF PUGET-SOUNDWHITE-CROWNED SPARROWS

Few studies have examined song variation in populations of birds over sufficiently long periods of time to demonstrate changes in the geogra phic distribution of song types. Baptista (1977) recorded songs of Pug et Sound White-crowned Sparrows (Zonotrichia leucophrys pugetensis) ov er much of their range in 1970 and 1977, describing six song dialects on the basis of differences in the terminal trills of songs. We docume nted the distribution of song dialects in the northern part of the ran ge of this subspecies in 1993 and 1994. The two most-widespread dialec ts have persisted, but the limits of their distributions have changed. One dialect with limited distribution in 1970 was not encountered. We describe two previously-undocumented dialects with limited distributi on, and identify sub-dialects whose distribution seems to be related t o barriers to dispersal. We have no reason to believe that changes obs erved are the result of selection for one song type over another.