Gerrit,

You are welcome to your opinions. However, your viewpoint is clearly a
minority one. The vast majority of scientific and popular literature about
Gyrfalcons refers to the three color morphs, and the vast majority of
individuals fit easily into one of these three morphs. For example, a good
treatment is found in the Peterson Field Guide to Hawks by Clark and
Wheeler, which describes and illustrates the white morph, gray morph, and
dark morph. The term "morph" (as in "polymorphism") is preferred by most
biologists and birders these days to "phase"; the latter term, as noted by
some, has temporal connotations.

I made reference in my message to the fact that there are individuals which
are intermediate among the different color morphs.
Thanks for pointing out that there are very rare "brown" adults. However,
the existence of intermediate individuals does not, as you seem to think,
invalidate the concept of color polymorphism. Color polymorphism is found in
many species of diurnal raptors, including such familiar species as
Red-tailed, Rough-legged, and Swainson's Hawks. In each of these, one can
find intermediate individuals, or birds that do not fall neatly into one of
the standard color morphs. It is still convenient and useful to speak about
"light-morph" and "dark-morph" birds, even if this does not describe a bird
as well as a feather-by-feather description would do.

At any rate, you seem to agree with me that there is no generally recognized
"brown morph" Gyrfalcon! The point I was trying to make is that virtually
all strongly brownish Gyrfalcons are immatures of the common gray morph, and
it is usually easy to tell by other features whether the bird is an adult or
immature.

Wayne C. Weber, Ph.D.
Delta, BC
contopus at telus.net




-----Original Message-----
From: tweeters-bounces at mailman2.u.washington.edu
[mailto:tweeters-bounces at mailman2.u.washington.edu] On Behalf Of Gerrit Vyn
Sent: November-15-10 7:55 AM
To: tweeters at u.washington.edu
Subject: [Tweeters] RE: Brown Phase Gyrfalcon (Wayne Weber)

Hello Tweeters,

Just wanted to chime in I post I saw that incorrectly corrects someones use
of the term "brown phase" gyrfalcon. Though unusual, there are in fact adult
gyrfalcons with brown plumage that superficially resemble juveniles. See
photo of an incubating bird linked below. It is also incorrect to say that
there are "three "color morphs or "phases" of Gyrfalcons: white, gray, and
dark." Gyrfalcons show a great diversity of color and pattern and range
from almost pure white to uniform brownish-black. Intermediate plumages form
a continuous gradation between the two extremes with no distinct breaks or
divisions. The terms morph and phase are used correctly when they apply to
birds with distinct, identifiable color patterns - this does not apply to
Gyrfalcon.

Take a look at the brown Gyrfalcon incubating here:

http://gerritvyn.photoshelter.com/search?I_DSC=gyrfalcon&I_DSC_AND=t&_ACT=se
arch



Best Regards,

Gerrit