[Tweeters] Leucism vs. albinism

Doug Schonewald dschone8 at donobi.net
Sat Mar 7 14:09:09 PST 2009


Tweets,

This is an interesting topic. Actually I believe there are very, very few
truly albinistic birds, and those seldom survive to adulthood, based on some
past research. Almost every bird that you see with white feathers is
leucistic, partially leucistic, or one of a number of other genetic
disorders such as Dilution, Ino, Schizochroism, etc. All are genetically
generated, but differ from albinism in that the coloring agents (eumelanin
and phaeomelanin) are present, but are either not transferred to the
feather or are present in lower amounts which creates diluted plumage
colorations. An excellent treatise on the subject can be found at:

http://www.vogelringschier.nl/DB28(2)79-89_2006.pdf

The paper was written by Hein van Grouw, longtime curator of the Natural
Museum of History - Netherlands in 2006 and is written in a way that us
common folks can understand most of it.

To be fair, a contrary paper using the terminology of albinism to describe
all white occurrences in plumage is:

http://elibrary.unm.edu/sora/JFO/v036n02/p0067-p0071.pdf

While Mr. Gross wrote this paper in 1965, most of his citations were from
the late 1800's with a couple from 1928 and 1957. I find his paper less
convincing since we have learned so much since then. Once thing in this
paper that is fascinating is the list of birds and bird families and the
occurrence of white in the feathering in each. Very good information, even
if it is slightly dated.

As far as terminology, I don't think it really matters. The terms albino,
partial albino, leucistic, and partial leucism have been used
interchangeably for years by both researchers and lay birders, and it
unlikely that it will change. However, understanding the processes at work
will help us better understand how and why birds sometimes look like they
do.
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