Comparative studies of vocal learning--The five recognized subspecies of white-crowned sparrow differ in several aspects of their natural history that might influence how and when songs are learned (Table). Results from laboratory studies of song learning by hand-reared males, conducted in collaboration with Peter Marler, have been published in Animal Behaviour in 1995 and 1996.

Males of the migratory Puget Sound and Mountain subspecies learn more tutor song types than do males of the sedentary nuttalli race. The great majority of song learning is concentrated in a senstive period in the first 2-3 months of life. Mountain white-crowned sparrows have a significantly shorter and earlier sensitive phase than Nuttall's males. We suggest that vocal dialects in the migratory subspecies result not from yearling males imitating adult males in their first breeing season, but from a process of selective attrition of song types during matched countersinging. In contrast, males of the sedentary nuttalli subspecies may rely more upon imitating the song of the neighbor they settle next to after dispersing.

 Nelson is currently studying song learning in Gambel's white-crowned sparrow. This subspecies is interesting because, in contrast to the first three subspecies listed in the Table, males do not form local song dialects. Instead, there are several different song types in a given location, and neighboring males do not share similar songs. He is currently studying a group of hand-reared males to discover how they may differ from the first 3 subspecies in the first year of vocal development.