That's interesting!! I hadn't imagined that plumage color could be affected
by dietary deficiencies during individual molts. Of course, I also don't
know of that many cases where there are different plumage colors in the same
bird species that are genetically determined, like hair color in humans. i
probably didn't make it clear enough that I was just proposing an example of
how genetics could result in that kind of outcome. There may be a lot of
alternative explanations for individual cases that are plausible. I have a
small flock of house finches in my yard - two of the males are red and one
is orange. I wonder why one of them isn't getting the same diet as the
other two? competition for food?? - Teresa
----------
From: owner-tweeters
To: tweeters
Cc: Tweeters
Subject: Re: hourse finch plumages - was orioles/genetics
Date: Wed, May 3, 1995 5:43PM

Teresa,

My reading and understanding of male house finch plumage is that the
yellow, gold, orange plumages are a result of a deficiency of beta-
carotene in the individual bird's diet when the colored plumage is
developing during each molt, and are *not* dependent upon genetics.

I have captured male house finches with red plumages, banded them, and
have re-captured the same individuals years later with yellow or 'orange'
plumage having replaced the red.

I will have to look up the reference for beta-carotene and get back to
you tomorrow...

Jon. Anderson
Olympia, WA
anderjda at dfw.wa.gov


On Thu, 4 May 1995, Michelsen, Teresa wrote:

> Sex-Limited: This is the case that could fit house finches (and according

> to my reference, accounts for the male peacock plumage). In this case,
all
> house finches have a gene somewhere for "basic" plumage, the brown streaky

> plumage that juveniles and females have. Both M and F birds have this
when
> they are born. Somewhere else there is another plumage gene that both M
and
> F birds also have, but which is only expressed in the presence of male
> hormones. So at some point in the male bird's life (bird puberty, if you
> will), genes on the W chromosomes get busy cranking out male hormones and
> the red plumage shows up in males, while the females stay brown. This
> second gene is further complicated by having both dominant and recessive
> traits (the red and gold varieties). As you can see, many bird species
fit
> this pattern.
>
> - Teresa Michelsen temi461 at ecy.wa.gov