These juvenile Glaucous
Gulls Larus hyperboreus were photographed in late September 2006 mostly at Kotzebue (a couple at Barrow), Alaska. They are presumeably of the form barrovianus, but I have my suspicions that some secondary contact with American Herring Gull or possibly Vega Gull or even Thayer's Gull took place in the recent past (genetically speaking) due to the incidence of birds with less-than-textbook wingtip and bill patterns: