Birds
Gull
Laridae · also called seagull
The gull, or seagull, is one of the most successful and least loved of birds: a grey-and-white opportunist that will eat a crab, a chick, a chip, or a bin bag with equal enthusiasm, and that has spent the last few decades moving off the cliffs and onto our rooftops.
Overview
Gulls are the family Laridae, around 50 species, found on every continent. They are typically grey and white with strong bills and webbed feet, and they range from the tiny little gull to the great black-backed gull, a 2 kg predator that kills other seabirds. There is no species actually called a seagull, and many gulls live inland on lakes, rivers, and farmland, not at the coast. They eat almost anything.
Life in the city
Several gulls, notably the herring and lesser black-backed, have moved into towns, nesting on roofs safe from ground predators and feeding on streets, parks, and landfill. Once established, urban colonies grow because the young return to breed nearby. Gulls also have salt glands above the eyes that let them drink seawater.
Two opposite trends
Gulls seem more numerous than ever because a few adaptable species are thriving around people. But many gull species have declined sharply at their natural coastal colonies, hit by changes in fishing, disturbance, predation, and disease, and the herring gull is now red-listed in Britain despite its city success.
Status
Gulls as a family are Not Evaluated. A few generalists are abundant and increasing; several specialist colonial species are in serious decline at sea, and a small number are globally threatened.
Gull: common questions
Is a seagull a real kind of bird?
Not as a species. Seagull is a loose everyday name for any member of the gull family, Laridae, and no bird is officially called just seagull. The name is also slightly misleading, because although some gulls are true ocean birds, many are birds of inland waters and farmland that rarely see the sea, and some, like the common gull and black-headed gull, are as at home on a playing field or a reservoir as on a beach. Birdwatchers and ornithologists always use specific names such as herring gull, lesser black-backed gull, or kittiwake.
Why do gulls come inland and nest on buildings?
Because towns offer what a gull needs. Flat and gently pitched roofs are safe from foxes and other ground predators that raid cliff and island nests, chimney stacks and parapets provide sheltered nooks, and there is a reliable year-round food supply from bins, streets, parks, landfill, and deliberate feeding. Once a few pairs succeed, their young tend to return to the same area to breed, so urban colonies grow. The same period has seen many natural coastal colonies shrink, so for some species the town population is now a significant share of the total, even as the birds become a nuisance through noise, mess, and nest defence.
Why do gulls sometimes seem aggressive toward people?
Almost always it is nest or chick defence, concentrated into a few weeks in late spring and early summer. A gull that dives at a person, calls loudly, or snatches at their head is a parent whose nest or flightless young are nearby, usually on a roof above, and it is trying to drive off what it reads as a predator. Outside the breeding season gulls are wary and keep their distance. The other situation people notice is food snatching, where gulls that have learned to associate people with food will grab an unguarded sandwich or chip, a learned behaviour that spreads within a population and is worst where people feed them.
Are gull numbers going up or down?
Both, depending on the species and where you look. The overall impression that there are more gulls than ever comes mainly from a handful of adaptable species doing well in and around towns and landfill sites. At the same time, several gull species have declined steeply at their traditional coastal and island breeding colonies, driven by reduced fish availability linked to changes in fishing and the sea, by disturbance and development, by predation from foxes and mink, and by outbreaks of avian influenza and botulism. In Britain the herring gull, one of the commonest urban gulls, is on the red list of conservation concern because of that colony decline.