Delayed plumage maturation in socially isolated juvenile zebra finches, Taeniopygia guttata

We investigated the effect of social variables on the regulation of the moult from juvenile to adult plumage in male zebra finches. Males reared in social isolation after day 31 after hatching retained their juvenile plumage until day 90; if then placed in a colony setting, they developed the typical male plumage in 2–3 weeks. The isolation-induced delay in male plumage resulted from a delay in the juvenile moult. Social isolates that could trigger song playbacks by pecking at a key developed male plumage at the same time as controls. We suggest that a nongonadal mechanism sensitive to social variables normally ensures that adult male plumage is acquired in zebra finches during the weeks leading up to sexual maturity. This is the first report of a social effect on moult.