Today I banded two after-second-year male American Redstarts. Redstarts have an uncommon molting pattern. After they hatch, they molt into a plumage that is very similar to females (see bottom photo), except that the males have a slightly orange tinge to their yellow sides. The males remain in this plumage through the following breeding season (their second year), after which they molt into their distinctive black and orange plumage. They retain this new plumage the rest of their lives. Thus, the next spring, black and orange birds are older than two calendar years.
Handbook of Bird Biology: Cornell Laboratory of Ornithology).