This pale gull was present off an on all day on Saturday, January 11, 2014 at Aurora Reservoir near Denver, Colorado. It was slightly smaller than nearby Herring Gulls, but towered over the numerous Ring-billed Gulls. Sitting, the back showed many second generation pale gray feathers, and the wing coverts were smudgy, rather than marbled, indicating a second-cycle gull. The bill was strongly pale-based, and small. In flight, the wings and tail appeared very pale. Photos were obtained very late in the day, when it was strongly backlit. I snapped a few shots as it flew by at eye level (from the north dam), before it flew off towards the northwest, appearing to depart the site just before dusk (maybe headed to the Valmont communal roost in Boulder County). Click on an image to enlarge.