Ever since someone reported a Snowy Owl near Mukwanago WI, there's been some discussion over whether it is a snowy or not. It was also mentioned that an albino Red-tailed Hawk had been seen in the area before but not since two years ago.
There are some that argue that the bird was the Red-tail but others that say it was a snowy. The original observer feels that the bird is indeed a snowy. I'm inclined to agree with him until proven otherwise. Snow Owls are very difficult to misidentify.
Mike Hendrikson at "colder by the lake" birding blog says otherwise. He says that he has had people misidentify such birds as Red-tailed and Rough-legged hawks and even crows or ravens and mistake them for Snowy Owls. Well... I believe Mike. He's an excellent birder and trip leader and he has a ton more experience than I do. I still can't get over how people can misidentify such a striking bird as a Snowy Owl though.
To give you an idea of how difficult it is, I've posted some pics that I've pulled of the web. (note, these are not my pictures and I lay no claim to them. I'm merely compiling them for comparison reasons) lol, I probably broke some kind of copyright law though.
anyway, these are not the worlds best comparisons but they do illustrate to a point the differences between Snowys and albino red-tails.
Note the posture. Snowys tend more to look like their leaning forward. Compare with the very upright posture of Red-tails.
I believe the picture below is copyright Mike Mcdowel. One of WI's top digiscopers.
Note in this pic the very upright posture that this hawk is maintaining.
This bird has more of the leaning forward posture that we sometimes see in Red-tails and may look more like a Snowy at a distance. Note though that this bird is quite a bit thinner looking than a snowy might look.
(sorry these aren't any bigger)
Note also that the general head shape is completely different. The red-tails look much more "hawk-like" than the rounded head of the Snowy Owl.
There are also differences in color between red-tails and snowys (not in these birds but in non-albino red-tails). I tend to think of red-tails having an off white breast. Almost yellowish in color. Snowy Owls are mostly pure white. I know of no color variations in the white coloring of these birds other than the black barring that some snowys display. Snowy owls tend to be pure white. Snow white. Rarely is the color an off white (unless the bird is dirty or something).
Here are some extra links about Snowy Owls. I've tried to keep the sources as respectable as possible.