This adult Mew Gull (Larus canus brachyrhynchus, a.k. "Short-billed" Gull) was among Ring-billed Gulls (L. delawarensis) at Horseshoe Lake in Loveland, Colorado on 20 March 2008. This very rare winter visitor shows up in the county about once per year.
These "witness" photos have not been adjusted in any way other than cropping and resizing. Pardon the low quality.