 By merely shifting position, feather regions of a muted-looking bird can instantly become fiery red or vivid green.In courtship displays for one example, males of the colorful Anna's hummingbird orient their bodies and feathers toward the sun to enhance the display value of iridescent plumage toward a female of interest.One study of Anna's hummingbirds found that dietary protein was an influential factor in feather color, as birds receiving more protein grew significantly more colorful crown feathers than those fed a low-protein diet.