Hummingbirds in general replace all their feathers yearly, but it can be a long process (especially the first molt for juveniles). Though young male Anna's start showing adult crown and throat feathers within the first few weeks out of the nest, it may take 9 months or more for them to get their full adult color. The process is similar in the highly migratory species, but they typically do their gorget, wing, and tail molt on the wintering grounds and come back to us in full adult plumage.