Gulls take 2-4 years to mature. The plumage during the juvenile and subadult years differs from the adult breeding plumage, and the plumage also differs between summer and winter. Thus, there can be 7 or so different plumages for each species of gull, making identification difficult. Presented here are photos of young gulls. Gull experts could sort them out, but it isn't worth it to me anymore.

Young gulls tend to be dark overall, including the bill.

Taxonomy: Charadriiformes, Laridae, Larinae.