Seagull

is a large white-headed gull with a distinctively heavy bill.]] Gulls range in size from the little gull, at and , to the great black-backed gull, at and . They are generally uniform in shape, with heavy bodies, long wing, and moderately long necks. The tails of all but three species are rounded; the exceptions being Sabine's gull and swallow-tailed gulls, which have forked tails, and Ross's gull, which has a wedge-shaped tail. Gulls have moderately long legs, especially when compared to the similar terns, with fully webbed feet. The bill is generally heavy and slightly hooked, with the larger species having stouter bills than the smaller species. The bill colour is often yellow with a red spot for the larger white-headed species and red, dark red or black in the smaller species. Gulls are a generalist species that can thrive in various environments and survive on a widely varied diet. They are the least specialised of all the seabirds, and their morphology allows for equal adeptness in swimming, flying, and walking. They are more adept walking on land than most other seabirds, and the smaller gulls tend to be more manoeuvrable while walking. The walking gait of gulls includes a slight side to side motion, something that can be exaggerated in breeding displays. In the air, they are able to hover and they are also able to take off quickly with little space. The general pattern of plumage in adult gulls is a white body with a darker mantle; the extent to which the mantle is darker varies from pale grey to black. A few species vary in this, the ivory gull is entirely white, and some like the lava gull and Heermann's gull have partly or entirely grey bodies. The wingtips of most species are black, which improves their resistance to wear and tear, usually with a diagnostic pattern of white markings. The head of a gull may be covered by a dark hood or be entirely white. The plumage of the head varies by breeding season; in nonbreeding dark-hooded gulls, the hood is lost, sometimes leaving a single spot behind the eye, and in white-headed gulls, nonbreeding heads may have streaking.

s are endemic to the Galapagos Islands.]] Gulls have a worldwide cosmopolitan distribution. They breed on every continent, including the margins of Antarctica, and are even found in the high Arctic. They are less common in the tropics, although a few species do live on tropical islands such as the Galapagos and New Caledonia. Many species breed in coastal colonies, with a preference for islands; one particular species, the grey gull, breeds in the interior of dry deserts far from water. Considerable variety exists in the Laridae family, and species may breed and feed in marine, freshwater, or terrestrial habitats. Two species of gulls dependent on human fisheries are Audouin's gull (Ichthyaetus audouinii) and lesser black-backed gulls (Larus fuscus); their breeding distributions (especially the black-backed gull) are heavily impacted by human fishing discards and fishing ports. Gulls in particular have high associations with salinity levels, which were found to be the main environmental predictor for waterbird assemblage.

===Diet and feeding=== Charadriiform birds drink salt water, as well as fresh water, as they possess exocrine glands located in supraorbital grooves of the skull by which salt can be excreted through the nostrils to assist the kidneys in maintaining electrolyte balance. Gulls are highly adaptable feeders that take a wide range of prey opportunistically. The food taken by gulls includes fish, and marine and freshwater invertebrates, both alive and already dead; terrestrial arthropods and invertebrates such as insects and earthworms; rodents, eggs, carrion, offal, reptiles, amphibians, seeds, fruit, human refuse, and even other birds. No gull species is a single-prey specialist, and no gull species forages using only a single method. The type of food depends on circumstances; terrestrial prey, e.g. seeds, fruit and earthworms, is more common during the breeding season, while marine prey is more common in the nonbreeding season when birds spend more time on large bodies of water. or on wet grass for earthworms. One method of obtaining prey involves dropping heavy shells of clams and mussels onto hard surfaces. While overall feeding success is a function of age, the diversity in both prey and feeding methods is not. The time taken to learn foraging skills may explain the delayed maturation in gulls. and also between orcas (the largest dolphin species) and kelp gulls (among other seabirds). Looking at the effect of humans on gull diet, overfishing of target prey such as sardines have caused a shift in diet and behaviour. Analysis of the yellow-legged gull's (Larus michahellis) pellets off the northwest coast of Spain has revealed a shift from a sardine to crustacean-based diet. This shift was linked to higher fishing efficiency and thus overall fish stock depletion. Human disturbance has also been shown to have an effect on gull breeding, in which hatching failure is directly proportional to the amount of disturbance in a given plot. Certain gull breeds have been known to feast on the eyeballs of baby seals and directly pilfer milk from the elephant seal's teat.

s nest colonially, but have tiny, closely packed territories.]] , with three typical eggs]] Gulls are monogamous and colonial breeders that display mate fidelity which normally lasts for the life of the pair. Divorce of mated pairs does occur, but it apparently has a social cost that persists for a number of years after the break-up. Gulls also display high levels of site fidelity, returning to the same colony after breeding there once and even usually breeding at the same location within that colony. Gull colonies can vary from just a few pairs to over a hundred thousand pairs, and may be exclusive to that gull species or shared with other seabird species. A few species nest singly, and single pairs of band-tailed gulls may breed in colonies of other bird species. Within colonies, gull pairs are territorial, defending an area of varying size around the nesting site from others of their species. This area can be as large as a radius around the nest in the European herring gull to just a tiny area of cliff ledge in the kittiwakes. Lasting between 22 and 26 days, incubation begins after the first egg is laid but is not continuous until after the second egg is laid, meaning that the first two chicks hatch at about the same time, and the third some time later. Young chicks are brooded by their parents for about one or two weeks, and often at least one parent stays behind to guard the chicks until they fledge. Although the chicks are fed by both parents, early on in the rearing period the male does most of the feeding and the female most of the brooding and guarding.

The family Laridae was introduced (as Laridia) by the French polymath Constantine Samuel Rafinesque in 1815. The taxonomy of gulls is confused by their widespread distribution zones of hybridisation leading to gene flow. Some have traditionally been considered ring species, but research has suggested that this assumption is questionable. Before the 21st century, 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. * White-winged gull is used to describe the four pale-winged, high Arctic-breeding taxa within the former group; these are Iceland gull, glaucous gull, Thayer's gull, and Kumlien's gull. In common usage, members of various gull species are often referred to as 'sea gulls' or 'seagulls'; however, this is a layperson's term and is not used by most ornithologists and biologists. The name is used informally to refer to a common local species (or all gulls in general) and has no fixed taxonomic meaning. In common usage, gull-like seabirds that are not technically gulls (e.g. albatrosses, fulmars, terns, and skuas) may also be referred to as 'seagulls' by the layperson. The American Ornithologists' Union combines the Sternidae, Stercorariidae, and Rhynchopidae as subfamilies in the family Laridae, but early 21st-century research shows this to be incorrect. A molecular phylogenetic study published in 2022 found the following relationships between the genera, including the most recent generic change: the placement of Saunders's gull in its own genus Saundersilarus. }} |2= }} |2= }} }} }} }} }} }}

This is a list of the 54 gull species, presented in taxonomic sequence. {| class="wikitable collapsible" |- ! Image ! Genus !Species |- | |Larus | *Pacific gull Larus pacificus *Belcher's gull Larus belcheri *Olrog's gull Larus atlanticus *Black-tailed gull Larus crassirostris *Heermann's gull Larus heermanni *Common gull Larus canus *Short-billed gull Larus brachyrhynchus *Ring-billed gull Larus delawarensis *California gull Larus californicus *Great black-backed gull Larus marinus *Kelp gull Larus dominicanus ("southern black-backed gull" or "karoro" in New Zealand) ** Cape gull Larus dominicanus vetula *Glaucous-winged gull Larus glaucescens *Western gull Larus occidentalis *Yellow-footed gull Larus livens *Glaucous gull Larus hyperboreus *Iceland gull Larus glaucoides ** Kumlien's gull Larus glaucoides kumlieni **Thayer's gull Larus glaucoides thayeri *European herring gull Larus argentatus *American herring gull Larus smithsonianus *Caspian gull Larus cachinnans *Yellow-legged gull Larus michahellis *Vega gull Larus vegae *Armenian gull Larus armenicus *Slaty-backed gull Larus schistisagus *Lesser black-backed gull Larus fuscus **Heuglin's gull Larus fuscus heuglini |- | |Ichthyaetus | *White-eyed gull Ichthyaetus leucophthalmus *Sooty gull Ichthyaetus hemprichii *Pallas's gull (or Great black-headed gull) Ichthyaetus ichthyaetus *Audouin's gull Ichthyaetus audouinii *Mediterranean gull Ichthyaetus melanocephalus *Relict gull Ichthyaetus relictus |- | |Leucophaeus | *Dolphin gull Leucophaeus scoresbii *Laughing gull Leucophaeus atricilla *Franklin's gull Leucophaeus pipixcan *Lava gull Leucophaeus fuliginosus *Grey gull Leucophaeus modestus |- | |Chroicocephalus | *Silver gull Chroicocephalus novaehollandiae **Red-billed gull Chroicocephalus novaehollandiae scopulinus *Huahine gull Chroicocephalus utunui (extinct) *Hartlaub's gull Chroicocephalus hartlaubii *Brown-hooded gull Chroicocephalus maculipennis *Grey-headed gull Chroicocephalus cirrocephalus *Andean gull Chroicocephalus serranus *Black-billed gull Chroicocephalus bulleri *Brown-headed gull Chroicocephalus brunnicephalus *Black-headed gull Chroicocephalus ridibundus *Slender-billed gull Chroicocephalus genei *Bonaparte's gull Chroicocephalus philadelphia |- | |Saundersilarus | *Saunders's gull, Saundersilarus saundersi |- | |Hydrocoloeus (may include Rhodostethia) | *Little gull Hydrocoloeus minutus |- | |Rhodostethia | *Ross's gull Rhodostethia rosea |- | |Rissa | *Black-legged kittiwake Rissa tridactyla *Red-legged kittiwake Rissa brevirostris |- | |Pagophila | *Ivory gull Pagophila eburnea |- | |Xema | *Sabine's gull Xema sabini |- | |Creagrus | *Swallow-tailed gull Creagrus furcatus |- |}

The Laridae are known from not-yet-published fossil evidence since the Early Oligocene, some 30–33 million years ago. Three gull-like species were described by Alphonse Milne-Edwards from the early Miocene of Saint-Gérand-le-Puy, France. A fossil gull from the Middle to Late Miocene of Cherry County, Nebraska, US, 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, Milne-Edwards' "Larus" elegans and "L." totanoides from the Late Oligocene/Early Miocene of southeast France have since been separated in Laricola.