VOCAL DEVELOPMENT IN BUDGERIGARS (MELOPSITTACUS-UNDULATUS) - CONTACT CALLS

Budgerigars have a complex vocal repertoire, some of which develops th rough learning. The authors examined the course of vocal development i n budgerigars from hatching to about 4 weeks postfledging (approximate ly 85 days old). Food-begging calls showed changes in duration, peak f requency, bandwidth, and frequency modulation with age. Within a week of hedging, each bird produced a contact call bearing a strong resembl ance to a shortened version of its patterned food-begging call. By 4 w eeks postfledging, budgerigar contact call repertoires often contained more than one call type, and there was clear evidence of sharing and imitation among the calls of parents, fledglings, and other social com panions. Perceptual testing showed that whereas acoustic variation in the structure of developing calls decreased both within and between ne stling birds, the discrimination of these calls was easier for adult b irds as young birds matured. These results suggest parallels with cert ain aspects of language development in humans.