Why do some birds have brightly colored feathers?

Bright plumage is usually the result of sexual selection and communication. In many species, vivid colors advertise fitness, because producing and maintaining them can require good nutrition and health. Some colors come from pigments such as carotenoids, while others come from feather microstructures that create iridescence, like the shimmer seen in many hummingbirds and peacocks. Bright coloration can also help species recognize each other or intimidate rivals. Birds use color as a kind of visual language.