Dark-eyed Juncos with white tails

I don't know how unusual this is, but 3 of 4 chicks from our dark-eyed junco nest have white tails this year. Both parents have normal dark tails with the white only underneath.
I have not seen white tails prior to these 3 juveniles.

Sandy

The bird in the photo looks slightly leucistic to me. The rufous mantle is paler than I would expect,asis the neck and throat.

Jim, I think this is a juvenile female from this spring (image taken a couple months ago) , and colours not fully developed yet.
Sandy

although juncos seem to be a species that is more prone to leucism than most, I suspect this bird is just molting? it clearly shows molt in the greater coverts, and it appears to show dark central rectrices (tail feathers) that are only about half grown in.

Sandy's junco's tail is, clearly leukistic, and after molt, it's replacement retraces will be devoid of pigment as well. A feather's structure and pigmentation are determined at the moment of each portion's formation at the germinative epidermal ring deep in the base of the follicle. The potential pigmentation and pigmentation pattern, and the physical structure of the rachis ( the central "stem/shaft) of the feather) the barbs, and barbules are all genetically determined and can be affected by a variety of possible mutations. Malnutrition and stress in response to a number of episodic or chronic stressors can produce segmental transverse feather defects as well as more pervasive feather malformations. A number of breeds of domestic fowl and even some caged bird species have been artificially selectively bred to maintain feather mutations that, in the wild state, would likely not permit survival, but in captivity can be maintained indefinitely through many generations.

Dave Graham, East River, SD