I have updated this caption after an excellent review of ablinism/leucism on the yahoo group birdspix by Joseph Morlan. Most of the opinions below the photo were made before this update and reflect the complexity of the subject and lack of standardized terminology. Some widely accepted definitions from the Cornell Laboratory of Ornithology are at: Cornell Leucistic is when all or parts of the plumage are washed-out or pale compared to normal. That's not the case with this Robin, where melanin is completely missing in patches on the bird. Cf. their example of a partial albino Spotted Towhee. The confusion stems from a definition of albinism apparently first suggested by Paul Buckley in which "albino" is all-or-nothing and all forms of partial albinism are relegated to the term "leucistic." Buckley, P. A. 1982. Avian genetics. Pp. 21-110 in M. Petrak (ed.), Diseases of cage and aviary birds, 2nd ed. Lea and Febiger, Philadelphia. “Perhaps more loosely and improperly used than any other term relating to color in birds, albinism is, no more and no less, the complete absence of all pigmentation, resulting in white feathers (for the reasons just discussed), pink eyes (no melanin obscures blood circulation, cause of the pink color) and light bills and legs/feet. Albinism is all or nothing, and a bird can no more be a “partial albino” than a female mammal “partially pregnant.” ...What is most frequently termed albinism by the layman is properly called leucism. It may be complete or partial, bilaterally symmetrical or asymmetrical, and may affect melanins, carotenoids and porphyrins differentially. Leucism is simply the complete loss of a particular pigment, or all pigments, in feathers but not in soft parts. It may be as slight as a single white primary feather on only one wing, or as pervasive as an all-white bird with normal eyes, bill and legs” (p. 65). In the 1985 edition of "A Dictionary of Birds" edited by Campbell and Lack. An entry by C.J.O. Harrison lists the following types of abnormal plumage: Abnormal Pigmentation, Atypical pigmentation, Schizochroism, Pigment replacement, Gynandromorphs, Pigment deficiency, Pattern variations, and Feather structure abnormalities. The following appears in the discussion under "Atypical pigmentation:" "Partial loss of pigment, affecting all the colours present and reducing them in intensity, is rare. It is called 'dilution' by bird breeders and 'leucism' in scientific writings, although the latter term is also used at times for various forms of schizochroic loss (see below) of single pigments which make the plumage appear paler...." I tend to agree with Joseph Morlans comment: "So defined, the phenomenon of true leucism (dilution of all pigments) is much rarer than schizochroism (involving a loss or dilution of only some pigments), so "leucistic" should probably be used rarely, and not merely as a jargon replacement for the more popular vernacular "partial albino." Photographed by Richard Stilwell in Iowa in July. Canon EOS D60 1/125s f/5.6 at 400.0mm iso200