Gulls In North America, Gulls And People
Gulls are 43 species of seabirds, in the subfamily Larinae of the family Laridae, which also includes the terns. Gulls occur in a wide range of coastal habitats, ranging from inland lakes, rivers, and wetlands, to marine shores and estuaries. Their distribution is virtually world-wide, but most species occur in the Northern Hemisphere.
Species of gulls range in body length from 8-32 in (20-81 cm). Their wings are long and pointed, and gulls have a short squared tail. The legs are short and stout, and the feet have webbing between the toes, useful for swimming. The bill is rather stout and hooked at the end.
Gulls are typically white-colored, with the wings and back, known as the "mantle," being colored gray or black. Some species have a black head during the breeding season. The sexes are alike in color and shape. Immature birds are usually much darker colored than the adults, but in a few species they are whiter.
Gulls are strong fliers, and they can undertake long-distance movements for purposes of feeding or during their migrations. Gulls often soar and glide effortlessly, whenever possible using the wind and updrafts to transport them where they want to go. Gulls are gregarious animals, both during the breeding season when they nest in loose colonies and during the non-breeding season when they often occur in large foraging and roosting flocks.
Gulls are highly omnivorous and opportunistic animals, eating a wide range of foods, depending on availability. However, they mostly feed on animal biomass, and less commonly on vegetation, especially fruits. Gulls are capable fishers, aerially spotting a fish as it
swims near the surface and catching it in their beak. This is usually done either by picking the food off the surface of the water, or sometimes by catching the prey after a head-long, shallow plunge into the water. Gulls also predate on the young of other seabirds when the opportunity presents itself. In addition, they scavenge carrion whenever it is available. Many species also scavenge the edible refuse of humans, near garbage dumps, fishing boats, fish-processing factories, and similar sorts of places.
Gulls nest in loosely structured colonies, generally building a mound-like nest out of grasses and seaweeds. Most species nest on the ground, but a few nest on ledges on cliffs. Gulls lay one to four greenish, speckled eggs, which are incubated by both sexes of the pair, which also share the raising of the young. Depending on the species, gulls can take as long as four to five years to reach sexual maturity. Some species of gulls are long-lived, and leg-ringed individuals have reached ages greater than 40 years.