[Tweeters] Leucism vs albinism

Bill and Nancy LaFramboise billnanl at verizon.net
Sat Mar 7 13:22:56 PST 2009


According to the Sibley Guide to Birds (pages 12-13), there is a difference
between albinism/partial albinism and leucism. It seems that these terms
are not interchangeable.

True or total albinism is the complete absence of color both feathers and
skin yielding white feathers and pink eyes. Partial albinism is used for
the scattered white feathers typically along a feather tract resulting in
white patches, totally white heads, etc. Evidently some birds are more
prone to this than others. We see this quite often in Dark-eyed Juncos and
sometimes in American Robins.

Leucism refers to birds with a faded appearance where typical patterns may
be present, but overall the bird looks paler. Quite a few American Crows
have been reported in the Lower Columbia Basin that look coffee colored or
lighter gray. (Pictures available)

While albinism is genetic, there has been speculation that leucism may be
dietary or otherwise environmentally caused (too much heat during incubation
?). We are not sure we can still find the article where we read about this.
Although we have never seen one of theses leucistic crows in molt, it would
be a great find as it might show whether or not black feathers were growing
in. Another point the article made was that sometimes during feather
formation, environmental factors (food, heat, injury) disturb feather
formation enough to cause white bars to form resulting in an evenly spaced
white stripe or bar especially across wing feathers.

Bill and Nancy LaFramboise
Richland WA


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