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We heard White-throated Sparrows singing in the
garden and
looked out to see this striking partially leucistic
White-throated Sparrow in Toronto on 28 April 2016. To
find out how to name this plumage, I consulted articles by
aberrant plumage expert Hein van Grouw. He describes leucism as "the
partial or total lack of both melanins in the feathers (and skin)."
This is an inherited condition in which the pigment cells are absent from
some or all the areas of skin where the feathers grow. "It varies
from a few white feathers (partially leucistic) to the plumage being
completely white." The bill and legs are the normal colour. This
White-throated Sparrow has normally coloured eyes, which is typical of all leucistic birds. All albino birds, however, have red eyes, so it's
not an albino. Reference: van Grouw, H. 2013. What colour is
that bird? The causes and recognition of common colour aberrations
in birds. British Birds 106:17-29. PDF available on line: |
