This bird was digiscoped on 23 April 2007 at the Larimer County Landfill in Fort Collins, Colorado (USA). I initially identified it as a first-cycle Lesser Black-backed Gull. Size, shape and plumage all seem correct but I am intrigued by the bicolored bill. LBBG usually maintain solid dark bills throughout their first cycle. For example, check out another first cycle LBBG from the same location a week earlier ( https://pbase.com/quetzal/image/76997924).
