The ring-billed gull, Larus delawarensis, is a common seabird that is frequently seen in areas such as beaches, estuaries, water bodies, fields, parking lots, and garbage dumps. It breeds from inland areas of the northern United States northward into central Canada. Ring-billed gulls spend the winter along coastal regions of North America, in the Gulf States, and in the southern portions of the American Midwest, as well as along the shores of the Great Salt Lake in Utah. The ring-billed gull is a common winter resident in northern Utah, and an occasional transient in other parts of the state. Although nesting colonies have been observed in northern Utah, there is insufficient evidence to believe that breeding occurs there.
Ring-billed gulls typically nest in colonies on rocky, sparsely vegetated islands in large lakes, on lake peninsulas, or on near-shore oceanic islands. In the west, colonies tend to be in close proximity to towns with croplands, which are popular foraging locations. In the east, there does not appear to be a relationship between human populations and the location of breeding colonies, presumably because the food source for the eastern populations is not directly related to human activities. Ring-billed gulls are omnivores; they eat a large variety of items that includes fishes, insects, worms, rodents, and grains. As opportunists, individuals will steal food from other birds, including members of their own species.
A pair bond is formed just before birds arrive at the nesting site; not only do the birds typically return to the same colony site each year, but they also usually select a nesting location in the same specific area of the colony each year. Typically a pair is monogamous for a breeding season, often selecting a mate from a neighboring breeding pair from the previous breeding season. The pair builds a nest of grasses and feathers on matted vegetation, either in the open, or in an area concealed by rocks. Two to four eggs are incubated for about three weeks; both parents share nest roosting duties, but the female spends more time on the nest than does the male. The young remain in the nest for a couple days after hatching, until they are able to walk. Both parents care for the young until they fledge at about five weeks at age, at which time the family group breaks up. The young will attain their adult plumage after three years.