By getting to know Ring-billed, Herring, and Great Black-backed Gulls, you'll be prepared to spot less common species, like this juvenile Laughing Gull, who I spied among the previously mentioned gulls on a Biddeford beach. Though not a rare bird in Maine, Laughing Gulls are uncommon in York county, visiting in small numbers primarily from May through October.
As is typical of gulls, juvenile Laughing Gulls tend to be uniformly brown, whereas adults are dressed to impress. By their 3rd summer, Laughing Gulls have usually attained adult plumage: clean white undersides, gray mantle, black hood with white eye-arcs, and reddish-black bill and legs. The only other hooded gull commonly seen in New England is the smaller Bonaparte's Gull. The two adults pictured here were photographed in May and August, respectively, in Biddeford Pool, Maine.
Learn more about Laughing Gulls, including listening to their laughter and viewing photos of non-breeding birds, over at All About Birds.