Ef. Brittanpowell et al., VOCAL DEVELOPMENT IN BUDGERIGARS (MELOPSITTACUS-UNDULATUS) - CONTACT CALLS, Journal of comparative psychology, 111(3), 1997, pp. 226-241
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.