This leucistic, or "white", Red Kite is a regular visitor to the Gigrin Farm feeding station. It's strikingly unusual colour is caused by a rare genetic mutation which prevents normal pigmentation of the feathers resulting in predominantly white or pale plumage. Since the eyes and bare parts (bill, cere and legs) retain their normal colours, it is not a true albino.
It was sad to see as the other 'normal' birds were mobbing it and keeping it from the food that they give them every day to help grow the Red Kite population as it wasn't long ago that they became an endangered species.