White markings tend to turn up in animals that are genetically evolved to (at least) tolerate humans. I'd guess wild animals that are used to living in cities are much more likely to develop colour mutations, its an indication of changes in the physiology and chemistry of the brain which occur with the development of tolerance of humans. I've seen a photo of a city
Fox with white legs, and the other day saw a beautiful melanistic
Fox that had been splat on the city ringroad in broad daylight.
Where I used to live in Somerset there was a colony of sparrows that often threw pure white specimins, they looked like white canaries. These were probably albinos, although I never got close enough to see the eye colour.