On some very rare occasions, I run into this leucistic Red-tailed Hawk. He is quite shy, so when I am in his territory, I am always fixing my camera settings for his stark white plumage and crank down the exposure compensation about -2/3's. I saw him in pursuit of a lady, so I stayed in the area just in case he came back. He did, but not very close. I stayed put and watched. He caught some pray, ate it and flew to a new perch but was still not close. I then saw him disappear behind a house, flying really low. I was hoping he landed. He did, he was in a pasture just a few yards from the road. I did a turn-around to put him in view through my drivers-side window and approached, ready to shoot. Now with hawks, you have about 3 seconds before they take flight, and I know this, but it seems every time, I think I can get away with getting a better view and blow the posed shot. I just gained focus when he took off. The last shot featured here is the first shot with him. Oh well, another day my white friend...another day.
Leucism (occasionally spelled leukism) is a general term for the phenotype resulting from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells capable of making pigment.
If you look at the crown/nape of this guys head (best represented in the first photo), you can see a dark pigmented area. Also, there is only 1 tail feather that is red (best represented in the 3rd photo), which is why I know its a red-tailed hawk. I know he is a "he" only because I saw him mating, so it was obvious he was a boy. I have photo'd him for more than 6 years so I fear his life left on earth won't be long, so every opportunity I get, I put in plenty of wait time in the field, because he is definately worth the patience it takes.
You can see other shots I've taken, by checking my labels for "white hawk" found on the right side of the template.