Here is another photo of this bird thanks to Cheryl Farmer again. In this photo you can see there are patches of feathers lacking melanin as well as normally pigmented feather patches. The photo in the previous post shows the face of the owl and you can see the bill and eyes appear pale as well. I have followed the terminology proposed by Jeff Davis in the Sept/Oct 2007 Birding magazine to describe this plumage because I agree that it does a much better job than some of the other terms previously used (ie. partial albinism).
A recent post to the Montana Outdoor Birding Group by Chad Adams provided a link to an article on albinism in Great Gray Owls. In this article the authors Pentti Alaja and Heimo Mikkola describe a number of Great Grays with abnormal pigments in Yellowstone National Park and in nearby Idaho. Bozeman is not that far (as the owl flies) from these observations.
This is a striking bird and apparently many birders went to find it today. Unfortunately some of them trespassed into private property to "get a better look" at this bird and then the neighbor who originally reported the bird to Cheryl was verbally abused by some of the birders when she told them they were trespassing. The original observer unfortunately now regrets telling anyone about the owl and Cheryl, who was very careful not to disturb this bird when she took these photos, is rightly upset that she led to these transgressions by alerting the general birding public to the location of the owl. This is a shame and I guess I expected better of my fellow birders there (I was formerly the president of the Sacajawea Audubon Society in Bozeman). The result will probably be that observers who care about the birds they see will not report interesting birds they see to protect the birds and avoid rude and inconsiderate behavior. We all lose then.
Alaja, P. and H. Mikkola. 1997. Albinism in the Great Gray Owl (Strix nebulosa) and Other Owls in Biology and Conservation of Owls of the Northern Hemisphere, Second International Symposium. USDA Forest Service General Technical Report NC-190. http://www.ncrs.fs.fed.us/epubs/owl/
Davis, J. N. 2007. Color Abnormalities in Birds: A Proposed Nomenclature for Birders. Birding 39(5)36-46