Adults have a white head, neck, chest, belly, and tail; gray back and wings; black primaries (flight feathers) with the outer two having white spots; yellow bill with a black band; and yellow legs and feet. Juveniles are variably mottled browns, with black bills and black primaries. 45 cm (17.5 in) in length; 122 cm (48 in) wingspan. Like most gulls, these birds show little difference between summer and winter plumage, but their immature stages are highly variable in plumage and for this reason can be difficult to identify.
The breeding season begins in early May and extends to early August. Breeding habitat includes inland lakes, rocky islands, isolated coastal areas, and sometimes islands in marshes. The Ring-billed Gull is a colonial nester, with many pairs nesting in the same area. The saucer-shaped nest is built on the ground by both adults out of grasses and other plant material. The nest is lined with finer grass and feathers. The female lays 1-7 (usually 2-4) eggs that both adults take turns incubating for about 21 days. The young are semiprecocial and are cared for by both adults. The young are able to swim at an early age and can fly when they are about 35 days old. They take 3 years to reach sexual maturity. Like other 3-year gulls, the Ring-billed Gull acquires a new and different plumage in each of its first three fall molts.
Non-breeding habitats are similar to the breeding season habitats, but also include more urban habitats such as parking lots and garbage dumps. The diet consists of a variety of materials, including fish, insects, small vertebrates, and in the winter, garbage. The Ring-billed Gull gathers food off the ground, or dives into the water while flying or swimming. This species is migratory.
Breeding populations of the Ring-billed Gull occur in north central and northwestern United States and in the Great Lakes region. Wintering birds are seen around the Great Lakes, all of the coastal United States, the southern half of the eastern United States, and south to southern Mexico and the Caribbean. In Georgia, this species is most common in the coastal areas during the winter, although birds may be seen throughout the state during migration.
This species is common and is not listed for any special conservation protection in any portion of its southeastern range.
The most similar eastern species is the Herring Gull. The Herring Gull is larger, being 64 cm (25 in) in length and with a 147 cm (58 in) wingspan. The Herring Gull is a highly variable species, but lacks the black band on the bill, has a red spot on the lower mandible (lower half of the bill), and almost always has pink legs and feet rather than the yellowish legs of the Ring-billed Gull.