Gulls (often informally called seagulls) are birds in the family Laridae. They are most closely related to the terns (family Sternidae) and only distantly related to auks, skimmers, and more distantly to the waders. Until recently[vague], most gulls were placed in the genus Larus, but this arrangement is now known to be polyphyletic, leading to the resurrection of several genera.
Gulls are typically medium to large birds, usually grey or white, often with black markings on the head or wings. They typically have harsh wailing or squawking calls, stout, longish bills, and webbed feet. Gull species range in size from the Little Gull, at 120 g (4.2 oz) and 29 cm (11.5 inches), to the Great Black-backed Gull, at 1.75 kg (3.8 lbs) and 76 cm (30 inches).
Most gulls, particularly Larus species, are ground nesting carnivores, which will take live food or scavenge opportunistically. Live food often includes crabs and small fish. Gulls have prophylactic unhinging jaws which allow them to consume large prey. Apart from the kittiwakes, gulls are typically coastal or inland species, rarely venturing far out to sea. The large species take up to four years to attain full adult plumage, but two years is typical for small gulls. Large White-Headed Gulls are typically long-lived birds, with a maximum age of 49 years recorded for the Herring Gull.
Gulls nest in large, densely packed noisy colonies. They lay two to three speckled eggs in nests composed of vegetation. The young are precocial, being born with dark mottled down, and mobile upon hatching.
Gulls—the larger species in particular—are resourceful, inquisitive and intelligent birds, demonstrating complex methods of communication and a highly developed social structure. For example, many gull colonies display mobbing behaviour, attacking and harassing would-be predators and other intruders. Certain species (e.g. the Herring Gull) have exhibited tool use behaviour, using pieces of bread as bait with which to catch goldfish, for example. Many species of gull have learned to coexist successfully with humans and have thrived in human habitats. Others rely on kleptoparasitism to get their food. Gulls have been observed preying on live whales, landing on the whale as it surfaces to peck out pieces of flesh.
The taxonomy of gulls is confused by their widespread distribution zones of hybridization leading to geneflow. Some have traditionally been considered ring species, but recent evidence suggests that this assumption is questionable. Until recently, most gulls were placed in the genus Larus, but this arrangement is now known to be polyphyletic, leading to the resurrection of the genera Ichthyaetus, Chroicocephalus, Leucophaeus, Saundersilarus and Hydrocoloeus. Some English names refer to species complexes within the group:
* Large white-headed gull is used to describe the 18 or so Herring Gull-like species from California Gull to Lesser Black-backed Gull in the taxonomic list below.
Hybridisation between species of gull occurs quite frequently, although to varying degrees depending on the species involved (see Hybridisation in gulls). The taxonomy of the large white-headed gulls is particularly complicated.
In common usage, members of various gull species are often referred to as sea gulls or seagulls. This name is used by the layman to refer to a common local species or all gulls in general, and has no fixed taxonomic meaning.
The American Ornithologists' Union combines Sternidae, Stercorariidae, and Rhynchopidae as subfamilies in the family Laridae, but recent research  indicates that this is incorrect.
List of species
This is a list of gull species, presented in taxonomic sequence.
* Pacific Gull, Larus pacificus
* White-eyed Gull, Ichthyaetus leucophthalmus
* Dolphin Gull, Leucophaeus scoresbii
* Silver Gull, Chroicocephalus novaehollandiae
* Saunders's Gull, Saundersilarus saundersi
* Little Gull, Hydrocoloeus minutus
* Ross's Gull, Rhodostethia rosea
* Black-legged Kittiwake, Rissa tridactyla
* Ivory Gull, Pagophila eburnea
* Sabine's Gull, Xema sabini
* Swallow-tailed Gull, Creagrus furcatus
The Laridae are known from fossil evidence since the Early Oligocene, some 30-33 mya. A fossil gull from the Middle to Late Miocene of Cherry County, Nebraska, USA is placed in the prehistoric genus Gaviota; apart from this and the undescribed Early Oligocene fossil, all prehistoric species were tentatively assigned to the modern genus Larus. Among those of them that have been confirmed as gulls, "Larus" elegans and "L." totanoides from the Late Oligocene/Early Miocene of southeast France have since been separated in Laricola.
1. ^ a b Pons J.-M. ; Hassanin A. ; Crochet P.-A.(2005) Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Molecular phylogenetics and evolution 37(3):686-699.doi:10.1016/j.ympev.2005.05.011
* Grant, Peter J. (1986) Gulls: a guide to identification ISBN 0-85661-044-5
Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License