This adult arrived at Lake Loveland gull hangout at 3:15 pm on 30 Dec 2013 and took off towards the Carter Lake nocturnal gull roost at 3:38 pm. The first photo was digiscoped with the sun at my back, from Taft Rd., looking towards the southeast. I then circled around to the swim beach in to get close enough to photograph without the telescope, but was shooting into sunlight.

Field marks indicating adult Kumlien's Gull (Larus glaucoides kumlieni) is the size (slightly smaller than Herring), small yellow bill with pale greenish tinge, small round lightly-marked white head with yellow eye, mantle paler gray than accompanying American Herring and Ring-billed Gulls, and limited, pale gray pattern on outer primary tips with extensive white mirrors.

This bird, with mostly white head and appearance of one dark outer primary on the left side when resting, is identical to a bird I reported as Kumlien's Gull in November at Horsetooth Reservoir in Fort Collins (about 8 miles northwest).

Click an image to enlarge.