[Umpqua Birds] Leucism and Albinism
- From: Robert and Jean Pollock <rjpollock@xxxxxxxxxx>
- To: umpquabirds@xxxxxxxxxxxxx
- Date: Wed, 5 Feb 2014 14:16:00 -0800
Hi Everyone,
Last week Jeannie and I were out at the BLM ranch on North Bank road
and we saw a flock of juncos that included one leucistic male. The
bird had a large white cheek patch on one side of its head and a
smaller white patch on the other. This bird, the leucisitic Red-tail
that we occasionally see near our house, and Matt's reports and
photographs of the leucistic Fox Sparrow (http://www.flickr.com/
photos/matthewghunter/sets/72157638840748645/) and the albino House
Finch, prompted me to review leucism and albinism in birds. I
thought originally that I would write a short article like the one I
did on hybridization and post it here, but I came across an excellent
article on the Cornell website and I decided to take the easy way out
and provide a link instead of preparing a detailed post. Here it
is: http://static.birds.cornell.edu/pfw/AboutBirdsandFeeding/
Albinism_Leucism.htm
Two interesting things are not mentioned in the article. The first
is that there are a number of mutations in birds which result in
white feathers other than the albinism and leucism mutations. White
Leghorn chickens are one example; they carry a dominant mutation
(albinism and leucism are associated with a recessive mutation) which
results in their feathers being white. I mention White Leghorns
because I did my dissertation on pigment cell development in the skin
of chick embryos. If you remove a small patch of skin from a White
Leghorn embryo and grow it in culture, pigment cells develop normally
as they would in the skin of embryos of colored breeds. There is an
inhibitory substance in the blood of White Leghorn embryos that
prevents pigment formation.
The other intriguing thing is the random nature of the size and shape
and location of the white areas in speckled leucistic birds. It is
difficult to understand how such a random arrangement develops in the
embryo, but obviously the pigment cells know what's up even though,
at present, we don't.
If you have any questions, I'll try to answer them.
Bob Pollock
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