Variation in the timing of vocal learning during the first year of life was studied in male song sparrows. Subjects were hatched in nests in the wild, reared in the laboratory from 2–10 days of age and tutored twice daily with tape-recorded songs from 10–350 days of age. Tutor songs were changed frequently. Half were conspecific and half heterospecific (swamp sparrow) songs. Timing of acquisition was determined by comparing analyses of crystallized songs with tape-recorded models for evidence of imitations. Learning began, on average, at 22 days of age and was heavily concentrated in the following 40-day period. Occasional cases of learning occurred as late as 200 days of age. There was a strong preference for conspecific songs. Imitations of songs acquired early in the sensitive period were more complete than those of songs acquired later. In song production, elements acquired at different times were sometimes detached from their original context and combined with others by a process of syntactical rearrangement. With the sensitive period defined in this manner, the song sparrow may be characterized as an “age-limited” song learner, as contrasted with species that are “age-independent” learners.