A re-evaluation of song development in the song sparrow.

Song sparrows were hand-reared from the egg in auditory isolation from adult conspecifics and maintained either together with other species or individually in sound chambers. Songs developed by the males contained several normal species-specific characteristics, but on the whole differed both qualitatively and quantitatively and were therefore readily distinguished from wild-type songs. The data are largely consistent with those of Mulligan (1966), but the normal aspects of song development have been over-emphasized in recent literature.