A large, black-backed subadult gull was photographed in Wellington, CO by Brad Biggerstaff on 11 March 2013. I photographed a similar bird about 10 miles away on 12 March 2013. Same bird? Photos are poor, but can we identify it?

Update: My personal opinion is that Brad's bird is whiter headed, shorter-billed, with more dark smudging on the inner half. If it is a different bird, what species? Structurally, it doesn't seem right for GBBG. Primary extension is too short for LBBG. Leg color is wrong for Western and Slaty-backed. What about Kelp (from South America)? Colorado has one previous record.

Update 15 March 2013 - Brad pointed out a dark line in the water behind the bird in his photograph making the bill look larger than it actually was. Given this info, Kelp is no longer a reasonable consideration. LBBG would be the most likely identification.