From Wikipedia: "Leucism // is a condition in which there is partial loss of pigmentation in an animal resulting in white, pale, or patchy coloration of the skin, hair, feathers, scales or cuticle, but not the eyes. Unlike albinism, it is caused by a reduction in multiple types of pigment, not just melanin."
Last Friday afternoon I was visiting Lora's Blind at South Llano River State Park near Junction, Texas (a marvelous park for birds by the way). The blind was a little slow, so I turned my attention to the Ladder-backed Woodpecker I could hear behind me. What I saw stopped me in my tracks. It was leucistic! What a find.
The opposite of leucistic is melanistic. Now to find a melanistic bird!