Gulls are long-lived and take up to 4 years to reach sexual maturity. Gulls form life-long pair bonds. Both parents assist in building the nest, defense of the nest, and care of eggs and young. Each pair produces 2 to 5 eggs per clutch and 1 clutch per year.
Gulls build nests on the ground. Most species nest in colonies, on sand and gravel-covered shorelines, and islands. They prefer to be able to easily spot threats and have quick access to water for escape.
Gulls are migratory and leave areas when bodies of water freeze.
Gulls prefer habitats with standing water and open landscapes with clear lines of vision. Urban areas, landfills, rooftops, and parking lots may be attractive sites for loafing and feeding.
Gulls feed on aquatic animals, terrestrial invertebrates, small vertebrates, remains of plants, carrion, and refuse. They frequently take the eggs and young of other seabirds. Small species, including ring-billed, laughing, and Franklin’s gulls, may feed on flying insects while in flight. Gulls steal food from each other and other species.