Great black-backed gull  (Larus marinus)

The great black-backed gull is classified as Least Concern (LC) on the IUCN Red List (1).

The largest of the gulls, the great black-backed gull (Larus marinus) is a dominating predator that has been described as a “merciless tyrant” due to its aggressive feeding habits. This powerful bird has a thick-set body with a large, yellow, red-tipped bill, strong legs and wide, webbed feet, which have a delicate pink hue. The breast and head are snowy white and sit in stark contrast to the black back and wings (3) (4) (5).

Young great black-backed gulls undergo several plumage changes before taking on that of the adult. Juveniles are pale brown with heavy white mottling, whilst immatures are also mottled, but have a distinctive whitish head and breast, with a dark-tipped, pale bill (2).

The great black-backed gull occurs along the coastlines of northern Europe and northern Russia, as well as the east coast of North America and Central America. The great black-black backed gull is also found around some inland seas or lakes, such as the Great Lakes of the U.S. It occasionally visits the coasts of northern Africa and southern Asia (1) (2).

The great black-backed gull is found in a variety of coastal habitats, including rocky and sandy coasts and estuaries, as well as inland habitats, such as lakes, ponds, fields and moorland. It breeds in areas free of or largely inaccessible to terrestrial predators, such as vegetated islands, sand dunes, flat-topped stacks, building roofs and sometimes amongst bushes on salt-marsh islands (1) (2) (5) (6). During the winter, the great black-backed gull often travels far out to sea to feed (7).

An opportunistic predator and scavenger with an omnivorous diet, there is little that the great black-backed gull will not eat. It feeds on fish, birds, small mammals, insects, eggs, berries, carrion and occasionally even large prey such as sickly lambs (1) (2) (5) (6). Small prey items are swallowed whole, but larger items are broken up before being consumed. Harder food items, such as molluscs and eggs, are dropped on hard surfaces to break them open (2) (7).

The great black-backed gull forages alone or in groups, from the shoreline to far out at sea (5). Groups of this gull and other seabird species often gather in areas where prey is in abundance, or follow humpback whales (Megaptera novaeangliae) to eat fish forced up to the surface. Prey is also pirated from other birds and scavenged from refuse dumps (5) (7).

The great black-backed gull forms breeding pairs in March or April, with pairs nesting in colonies with the herring gull (Larus argentatus), and occasionally with other species (2) (5). Both the male and female scrape several nests into the ground, but the nest site with the best shelter from the prevailing wind is chosen, usually behind a large object such as a log or rock. The nest is then filled with grass, moss and seaweed (2) (5). One to three eggs are laid over a six day period, between late April and late June. The eggs are incubated for up to 28 days by both adult birds, which continue to care for the chicks after they have hatched, alternating between foraging for food and protecting the young. The chicks fledge after seven or eight weeks, but are cared for by the adults for up to six months. Sexual maturity is reached at four or five years (5).

Historically, the great black-backed gull was harvested for its eggs and feathers, which were used in the hat-making trade, and this species was removed from large parts of its range as a result of this exploitation (7). Today however, its adaptability to human presence and the use of urban environments as artificial nesting sites has resulted in the great black-backed gull rapidly increasing in number and range. It is now a widespread and abundant species and its numbers have increased to such high levels in some areas that it is often seen as a pest species, especially near airports where it risks collisions with airplanes, and in some coastal areas where it predates upon and competes with rarer seabirds (5).

Although there are no known major threats to the great black-backed gull, high levels of toxic pollutants, which are ingested with contaminated prey, are often found in individuals and eggs, reducing reproductive success. Breeding is also interrupted by human disturbance, which can lead to eggs being abandoned, leaving them vulnerable to exposure and predation. The great black-backed gull is also hunted for sport in Denmark (1) (6).

In the absence of any major threats, the great black-backed gull has not been the target of any known conservation measures. In fact, most management plans for this species have centred on controlling its numbers, so to conserve other seabird species. These measures are only effective on a small scale and so do not greatly affect global population numbers (5).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

More information on the conservation of birds:

• Royal Society for the Protection of Birds:
  http://www.rspb.org.uk/

 More information on the great black-backed gull and other bird species:

• BirdLife International:
  http://www.birdlife.org/