Ross's above. Shorter bill, their mouth appears to close completely and they have a warty like surface on the bill nearest the face.

Below are a couple Snows (not the greatest pic), both a regular and a blue phase. Beak is more stream lined, and they look almost like they have lips because the bill does not quite close tightly mid-length. Also body size is about 1/3 rd larger than Ross's.
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Another couple snows
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And a common and blue phase Ross.
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Blue phase birds are rare here in the Pacific flyway. Like 1 in 5000 birds.

Very common in the central flyway.

Last edited by 1minute; 04/07/17.

1Minute