This first-cycle gull was photographed March 28, 2007 in the Coastal Plain near Houston and Galveston, Texas; note the size compared to the two adult LBBGs (but note that there is some Size Illusion at play; it is the size of a small/medium American Herring Gull), the overall structure (esp. the head and bill), and the extent of molt - might this be some type of Yellow-legged Gull?:
