According to the literature, Leucism is a pigmentation problem where some or all of a birds feathers are of a different than normal colour, often white. Reportedly the colour variations or patterns are usually symetrical. For more information and description on leucism in birds, see http://birding.about.com/od/identifyingbirds/a/leucism.htm .
I previously posted several images of this leucistic crow. At that time I indicated that it appeared that the other (normal) crows were harassing it on account of it being different. It now appears that I was probably wrong. The fighting amongst the crows seemed to have been merely a lover's quarrel. The leucistic crow now appears to have acquired a mate and it and its mate are now mostly seen together or as part of a group of crows.
Top Image: The leucistic Crow (top) and its mate perched up high in a tree in one of my neighbours yards.
The leucistic Crow takes off. Its mate followed shortly.
The leucistic Crow in full flight.
After a brief stop on an other neighbours roof, the leucistic Crow takes off again after its mate.
Note: the white backgound is a due to a white gable end of the adjacent house and not the sky. The sky was blue at the time.