I have seen this raven (or crow) several times in my garden lately. It has two white feet that appear to be damaged or deformed. It is able to land and walk on them but does appear to have some difficulty. In a close up photo of the legs and feet there are possibly two small metal fittings which make me wonder if they are artificial feet fitted to an injured bird. With its white feathers there is evidence of leucism but I was not aware this might extend to its legs and feet. All ideas welcome. Photos attached.
Thanks Germain. It came back in today and I managed to get a good close up shot of its leg and foot which certainly confirmed your diagnosis. It appears to have a mate with it who (I am happy to say) has no sign of the scaly leg mites but who was very protective of its injured companion.