Hello Hans and Wayne.


One of the many interesting things about birds and birding is that the observer's learning never ends.


I quote from the researchers and experts at Cornell Ornithology:




"'The Gyrfalcon shows extreme variation in plumage color and pattern, exhibiting a range from almost uniform white to uniform brownish-black. Intermediate plumages form a continuous gradation between the two extremes with no distinct breaks or divisions. Although not uniformly agreed upon (see Potapov and Sale 2005 ), use of terms that describe distinct, identifiable color patterns such as ?morph? or ?polymorphism? for Gyrfalcons is incorrect ( Cade et al. 1998 , Flann 2003, Cade 2006 ) and misleading. For convenience, most birds are lumped into one of three generalized descriptors: white, gray/intermediate, and dark "variants". Each group is described in terms of a range of patterns and colors. White variants have a large proportion of background color to marking color; reverse is true for dark variants; gray/intermediate variants have intermediate amounts of both. The change in proportions results from changes in length and width of shaft-streaks on spotted and streaked feathers (generally on head and ventral body surfaces) and in completeness of barring on barred feathers (generally on mantle, wings, tail, and legs). In complete barring, dark bars are continuous from one lateral edge of feather to the other with bands of light background color between; in incomplete barring, background color on either side of shaft is interrupted in middle by darker marking color.



Dark variants overall Van Dyke brown, except breast and belly background varying from pale neutral gray (86) to pale pinkish buff (121D) heavily streaked (anteriorly) and barred (posteriorly) with Van Dyke brown; tail neutral gray strongly barred with Van Dyke brown, darker color often mottling lighter color, barring faint in darkest individuals; primaries and secondaries pale horn mostly obscured with heavy irregular sepia barring or heavy mottling; underwing coverts and axillaries heavily barred with Van Dyke brown, leaving only small spots or barring of white background."




Bud, what are your thoughts?




Best regards

Dan Reiff



----- Original Message -----
From: "Hans-Joachim Feddern" <thefedderns at gmail.com>
To: "Wayne Weber" <contopus at telus.net>
Cc: "TWEETERS" <tweeters at u.washington.edu>
Sent: Sunday, November 14, 2010 10:24:48 PM
Subject: [Tweeters] Re: Brown phase Gyrfalcon?

Wayne,

Thank you for the clarification! All Gyrfalcons I have ever seen in the wild, including along the Hulahula River in the Brooks Range in Alaska, have all been gray morphs. The only white morph I have ever seen, was many years ago in Germany, kept by a falconer. Needless to say, a brown Gyrfalcon had me consult a field guide. There it was on page 123 of the combined Eastern/Western Peterson "Field Guide to the Birds of North America": Brown Morph in flight and head only! In the meanwhile I have checked in half a dozen other field guides and reference books and you are absolutely correct!
The lesson learned from this, is "Thou shalt not use only one field guide!". Come to think about it, I did not even look at Sibley - I wonder if he is correct? Of course would "phase' not be a juvenile form on the way to adulthood?

Cheers,

Hans Feddern
Twin Lakes/Federal Way, WA.
thefedderns at gmail.com


On Sat, Nov 13, 2010 at 10:40 PM, Wayne Weber < contopus at telus.net > wrote:






Tweeters,



A recent message made reference to a ?brown phase? GYRFALCON. For the record, there is no such animal. The birds sometimes referred to as ?brown phase? are actually immatures of the gray morph or gray phase. Their plumage is much browner than that of adults, and they are usually heavily streaked on the underparts-- both of these features making them pretty easy to tell from adults.



There are three color morphs or ?phases? of Gyrfalcons: white, gray, and dark (blackish), as well as, undoubtedly, a few individuals that are intermediate. In Washington and elsewhere along the Pacific coast, virtually 100% of the birds we see are gray-phase. There is no brown phase?they are just the immatures of the gray phase.



Wayne C. Weber

Delta, BC

contopus at telus.net





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