> From: "Jim Rosso" <jlrosso at classic.msn.com>

> This reminds me of being back in California and down in the Monterey area and
> seeing Heermann's Gulls with a large white patch in their wings.
snip
> We never saw
> these birds north of Monterey, only south.
>
I have seen such birds in Humboldt bay, 400 miles or so north of
Monterey. The explanation that I got is that these white patches are
a naturally occuring genetic expression that shows up in about 10%
of immature Heermann's Gulls (this may just be the percentage for
that area).

We also had a Dark-eyed Junco with striking white eyebrows spend a
winter in our backyard when we lived in CA.

In the cases we have been discussing, the causes are very likely
genetically based. Albinism is not a new trait, and, as with
anything genetic, expression varies over different populations and is
usually dependent on local (or regional) pressures on the organisms.
An often cited example of this is the high rate of sickle-cell anemia
in people of African descent because the heterogenous condition gave
these individuals an advantage in resisting malaria. Since
Caucasians in Europe didn't have the environmental pressure of
malaria to contend with, those without sickle-cell alleles had an
advantage resulting in a much lower rate of sickle-cell among
Caucasians.

What it all boils down to is that when you see a change in frequency
of occurence of any character there is often, *but not always*, a
change in environmental pressure. Before rushing to blame
environmental toxins or ozone depletion, one should look at the
pressures that "maintained" these populations in the first place and
see if there has been a change. Working this way may well lead back
to environmental toxins or ozone depletion, but we could just as
easily find that humans moved in, displaced natural predators with
cats, and now the cats are being kept inside, removing a predation
'problem'.

Remember, change is normal, and not every change is bad. To
interject a personal opinion, many so called environmental
restorations and improvements have been misguided by the belief that
things should be returned to some former state, and once there should
always remain in that state. That's not natural, and if you walk out
your door and look around, remember that everything you are looking
at is barely a blink in geologic time.

As far as the albinistic birds go, keep watching for them, and keep
watching for other changes that are allowing these birds to survive.
I would not be concerned about the albinistic birds themselves, but
instead with the reasons they are surviving, especially if a shift
in frequency can be documented.
jw




Jane Westervelt
Steve Kalloger
Moscow, ID