This is a Partial albino chickadee due to the pink legs and unusual coloring on the upper body.
Albinism is a pigment (melanin) deficiency that occurs rarely among birds and mammals, even including humans. The effects among birds vary from a few white feathers to all-white plumage. A true albino bird is very rare. It would have no pigment in its feathers, bill or legs and its eyes would appear pinkish-red, because the blood vessels can be seen when the typically dark color is missing.
Albinism is normally caused by a genetic mutation that can be inherited if both parents have the albino gene. If it's hereditary, then a new set of feathers will carry the same white pattern.
