Until the 21st century, most gulls were placed in the genus Larus, but that arrangement is now considered polyphyletic, leading to the resurrection of several genera.

[1] An older name for gulls is mews; this still exists in certain regional English dialects and is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse, and French mouette.

[2][3][4] Typically medium to large in size, gulls are usually grey or white, often with black markings on the head or wings.

[7] Gulls are resourceful, inquisitive, and intelligent, the larger species in particular,[8] demonstrating complex methods of communication and a highly developed social structure.

[9] Certain species, such as the herring gull, have exhibited tool-use behaviour, for example using pieces of bread as bait with which to catch goldfish.

The wingtips of most species are black, which improves their resistance to wear and tear, usually with a diagnostic pattern of white markings.

Considerable variety exists in the Laridae family, and species may breed and feed in marine, freshwater, or terrestrial habitats.

[15] Gulls in particular have high associations with salinity levels, which were found to be the main environmental predictor for waterbird assemblage.

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.

Dipping is common when birds are sitting on the water, and gulls may swim in tight circles or foot paddle to bring marine invertebrates up to the surface.

[18] One method of obtaining prey involves dropping heavy shells of clams and mussels onto hard surfaces.

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.

[22] Lastly, closure of nearby open-air landfills limited food availability for the gulls, further creating a stress on their shift in diet.

Analyzing both adult and chick remains, researchers found a mixture of both natural prey and human refuse.

These temporal shifts from marine to terrestrial prey highlight the resilience of adult gulls and their ability to keep chick condition consistent.

Divorce of mated pairs does occur, but it apparently has a social cost that persists for a number of years after the break-up.

Within colonies, gull pairs are territorial, defending an area of varying size around the nesting site from others of their species.

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.

[30] 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.

The name is used informally to refer to a common local species (or all gulls in general) and has no fixed taxonomic meaning.

[31] 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[32][33][34] 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.

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.