All,
I looked at many large water bodies in Boulder County this morning. Best birds were 14 Snow Geese at the east end of Dodd Res, which is east of Niwot, and Pacific Loon and 2 Bonaparte's Gulls at Boulder Res.
I looked through probably 5000 Cackling Geese at Dodd, Six-Mile and Baseline Res, but didn't come up with anything dark, such as Brant, Scoters or a juvenile Jaeger.
Cheers, Peter Gent.