Smallest gull in the world with short legs, wings, and bill with an overall squat appearance. Breeding adults have a black head, gray back, and white wingtips. Nonbreeding adults have a black ear patch and cap on the back of the head. Wingtips whitish with dark underwings, especially noticeable in flight. Younger birds similar to nonbreeding adults but with a black "M"-shaped pattern on wing, especially noticeable in flight. When perched, this looks like a thick horizontal stripe across the wing and shoulder. Some individuals show faint pink wash on belly. Most similar to Bonaparte's Gull but even smaller and more compact with white wing tips. In North America, usually found singly among flocks of Bonaparte's Gulls on lakes, beaches, estuaries, or bays. Main population found in Europe; rare breeder in marshes in Canada.