Mystery Birds You Already Know
Birds can change their appearance during the year. This happens when birds molt. That means they replace all of their feathers. This can happen two or three times per year. Old, worn feathers fall out (not all at the same time!) and are replaced by fresh feathers. In the breeding season these new feathers are often much brighter than they are in the fall or winter.
The same thing happens as birds mature. A three month old bird can look much different than an adult of the same species. Surprisingly, even a bird's beak color can change during the year. Here are some examples of Mystery Birds that can certainly fool you!
European Starling - nonbreeding plumage and breeding plumage
American Goldfinch - non-breeding plumage and breeding plumage
Little Blue Heron - immature and adult
White Ibis - juvenile and adult