Did you know that Brown finches that turn yellow are American Goldfinches?
These 4-5 inch long birds, with a wingspan of 7-9 inches, change from having dull winter feathers to brilliant breeding plumage in the spring. American Goldfinches are unique in that all four subspecies molt in both spring and fall.
In September, following the breeding season, American Goldfinches shed their feathers completely. Males lose their canary plumage, and their black wings and tails, marked with white bars, turn dull black, with buff-colored bars. They regrow dull, medium-brown or tan body feathers with an olive tinge and some yellow at the shoulders and face. They will lose their black caps completely.
In spring, American Goldfinch males transform into breeding birds with brilliant lemon yellow feathers.
Their bright white rumps, contrasting with their bright black and white wings and tails, are visible in flight. Males grow black caps as they adopt plumage designed to attract a female. Even their bills change from black to a brilliant orange for the breeding season of July to September.
Females are a dull yellow-brown shade all year, though their plumage does turn slightly more yellow after the spring shed.