ALBINO, LEUCISTIC AND MELANISTIC
Many people have seen birds that should be colorful, but are instead completely white, mostly white or have patchy white spots where colorful feathers should be. Other birds that should be colorful appear to be very darkly colored or with dark feathers where lighter ones should be. These birds all have a genetic mutation which is expressed either in just their feathers or in all parts of their body.
Pure white birds are Albino. They have a genetic mutation where they do not produce melanin, the pigment that causes color in skin, feathers, scales and the iris of the eyes. This mutation also occurs in humans and other animals. The absence of pigment in the iris causes the eyes to appear red, as all you see are the blood vessels that feed the iris.
Leucistic birds are able to produce melanin, but the color is not expressed in some or all of their feathers. Pigment is usually expressed in their irises, however, so their eyes are usually colored, as are their feet and bills. This is the easiest way to tell if a bird is albino or leucistic. Some leucistic birds are called "piebald" or "pied" when they have a feather pattern that looks like a patchwork quilt. Marilyn Meadows photographed a leucistic "piebald" Black-Chinned Hummingbird that was coming to one of her feeders.
This leucistic (Piebald) Anna's Hummingbird was photographed on March 5, 2019 in Pasadena, California
Below are pictures of Reggie, an adorable melanistic Barn Owl who lives at The Hawking Centre in Doddington, Kent, UK
Melanistic birds, on the other hand, have a genetic mutation that makes them produce too much melanin, so their feathers are darker than normal. These birds also can be completely dark or have larger than normal dark markings of their usual feather patterns. Albino and leucistic hummingbirds generally have a short lifespan. Their feathers are not as strong as normal, and their light coloring makes them more easily spotted by predators. The males have a particular problem, as they lack the bright coloring that usually attracts a mate. Melanistic birds, however, are much better camouflaged from predators, but they have the same problem when it comes to attracting a mate.