Red Tailed Hawk (Leucistic)
Leucism is a genetic condition in which parts or all of an animal's body surface lack cells capable of producing any type of pigment. (The word is derived from the Greek word leukos, meaning "white".) You may be familiar with Piebald horses, known for their splotchy "paint" pattern. These horses are actually leucistic!
Leucism is similar to albinism (and frequently mistaken for it), however, albinos lack the ability to create melanin, one specific type of pigment. Leucistic individuals usually have normal eye color, unlike albinos, which generally have red eyes.
Because the frequency of leucism in a given species is dependent on the population size, it's not surprising that there is a relatively high occurrence of leucistic Red-tailed Hawks. (Another frequently-seen leucistic bird is the American Robin.)