Doug Nelson is studying several aspects of vocal development in the white-crowned sparrow. This species has been studied intensively for over 30 years now, because of the fascinating degree of spatial variation in its song. Peter Marler's classic studies demonstrated that males form local song dialects, in which neighboring males sing very similar songs which differ from the songs of males recorded several kilometers away. He also demonstrated that young males learn their songs, so that songs are passed from one generation to the next in a system of cultural inheritance. Males readily imitate tape-recorded songs in the laboratory, making them ideal subjects for the study of song development. Adult males sing a single song type, but prior to "crystallizing" this song juveniles often sing 2-8 different song types. Nelson's current research focuses on different aspects of this "song overproduction" process.