Ring-billed Gulls are medium sized, white-headed, primarily inland-nesting North American gulls that frequent garbage dumps, parking lots, and southern coastal beaches in large numbers during winter. This species was nearly wiped out by human persecution and development between 1850 and 1920, but has since rebounded to become a common and familiar bird. An estimated 3 to 4 million individuals inhabited North America in 1990, whereas Breeding Bird Survey (BBS 2011, Sauer et al. 2011) data in 2009 suggested that this number had increased 250%. In some localities this gull is considered a pest and various measures are used to control its numbers, most with limited success.
Ring-billed Gulls are opportunistic feeders that mostly eat insects, earthworms, fish, rodents, and grain. They nest on the ground in colonies on sparsely vegetated islands in large lakes, and occasionally on mainland peninsulas and on near-shore oceanic islands. Eastern breeders share nesting habitat with Herring Gulls (Larus argentatus), Great Lakes breeders with Caspian and Common terns (Hydroprogne caspia and S. hirundo), and western breeders with California Gulls (Larus californicus). The breeding biology of the Ring-billed Gull is well known and the history of its populations during the last century well documented.
Based on morphology and displays, this gull is closely related to other typical white-headed gulls; it has hybridized with Mew (Larus canus), California, Franklin's (Leucophaeus pipixcan) and Laughing gulls (Leucophaeus atricilla) (Moynihan 1959a), among others. However, genetic analyses are required to establish its phylogenetic relationships with other gulls.
Important bibliographies on the Ring-billed Gull are: Clapp et al. (Clapp et al. 1983c), that contains summaries of numerous aspects of the species' biology with 276 references from 1907–1983, and Smith (Smith 1986a) that lists 333 references between 1935–1986. Locations of spirit and skeletal collections are given in Wood et al. Wood et al. 1982 and (1982b), respectively. A recent summary of the status of Great Lakes populations can be found in Morris et al. (2011).