Justification This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Family/Sub-family Laridae

Species name author Linnaeus, 1758

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Christidis and Boles (2008), Cramp and Simmons (1977-1994), Dowsett and Forbes-Watson (1993), SACC (2005 + updates), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Taxonomic note Larus cachinnans (Sibley and Monroe 1990, 1993) has been split into L. cachinnans and L. michahellis; L. armenicus (Sibley and Monroe 1990, 1993; AERC TAC) has been lumped into L. michahellis. These changes to the BirdLife checklist follow examination by the BirdLife Taxonomic Working Group (BTWG) of a recent review of large white-headed gulls in the Holarctic by Collinson et al. (2008) and associated literature referred to therein. The following species level treatment, shown with subspecific placements, has been adopted by the BTWG: L. fuscus (with intermedius, graellsii, heuglini, taimyrensis and barabensis); L. argentatus (with argenteus, smithsonianus, vegae and mongolicus); L. michahellis (with atlantis and armenicus) and L. cachinnans. This treatment is based on evidence of sympatry, and morphological and behavioural differences, but rejects further splits derived from phylogentic analyses based on mtDNA because Collinson et al. (2008) admit that (1) mtDNA lineages can disappear by random events, resulting in misplacements and displacements in phylogenies, and (2) hybridisation, which seems very widespread in these white-headed gulls, can result in "adoption" of mtDNA sequences by another taxon, completely obscuring the real situation. Collinson et al. (2008) explicitly state "these complications do not just make gull phylogenies difficult: they may cause entirely false conclusions to be drawn about species boundaries… it must be recognised that splits or lumps based solely on mtDNA cannot be regarded as robust". While proposed splits not adopted here are not based solely on mtDNA, the morphological evidence presented is not conclusive, taxa are only diagnosable in some cases and there is hybridisation between them.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

910,000 - 1,100,000

unset

736,000 km²

No

Range & population The Lesser Black-backed Gull breeds from the central-north of Russia, around Scandinavia, Germany, Belgium, the Netherlands and northern United Kingdom to Iceland. It also breeds year-round on the coast of Portugal, southern Ireland, the United Kingdom and northern France, and one seasonally breeding population is found in north-east Spain. Seasonal breeders disperse widely, expanding its range to include the entire North Sea coast, much of the Mediterranean, Black Sea and Caspian Sea coasts, the northern and eastern coasts of Africa (including rivers inland), and around the Arabian Peninsula to north-west India¹.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour Most populations of this species are fully migratory¹ and travel in leapfrog-like stages¹, using many stopovers en-route². The Autumn migration is started by the non-breeding birds in late-June, the breeding birds following from late-July to September². The return migration takes place between February and late-June¹, with the species arriving at breeding colonies from March onwards, and breeding from May or late-April to mid-June¹. It breeds colonially^{4, 5}, often with other gull species (especially Herring Gull Larus argentatus)⁵, in colonies ranging in size from a few pairs⁶ to several tens of thousands⁴. Outside of the breeding season the species remains gregarious, normally migrating singly or in small groups of less than 10⁷, and often feeding in flocks of hundreds of individuals on rubbish dumps or over shoals of fish at sea^{6, 7}. It may also feed singly or in small groups⁷. In its African wintering grounds the species may roost communally during the day on salt or fresh waterbodies^{7, 11}. Habitat Breeding The species breeds on coastal grassy slopes (flat and unbroken)⁴, sand-dunes^{4, 5}, cliffs^{1, 4, 5}, rocky offshore islands^{1, 5}, saltmarshes⁵, and on inland habitats such as the margins of lakes^{2, 4}, high moorland^{4, 5}, and islands in lakes and rivers² . It shows a preference for well vegetated sites, with fairly close, short vegetation^{6, 4}, and may forage on arable land, pasture land⁴, and on refuse dumps^{1, 4}. Non-breeding Outside of the breeding season the species chiefly inhabits inshore and offshore seas⁶, as well as lagoons, estuaries, harbours and seashores in the tropics⁶. It may also frequent inland habitats during this season, such as large lakes and rivers⁷, in England preferring flooded gravel pits and reservoirs, canals, river weirs, flood-lands and sewage treatment areas⁶. As in the breeding season it is often seen foraging on arable land, pasture land⁴, and on refuse dumps^{1, 4}. Diet The species is an omnivorous, opportunistic feeder³ that forages extensively at sea. Its diet consists of small fish (especially Baltic herring Clupea harengus)¹, aquatic and terrestrial invertebrates (e.g. beetles, flies and larvae, ants, moths⁷, grasshoppers², crustaceans, molluscs, segmented worms and starfish⁷), bird eggs and nestlings, carrion, offal¹, rodents, berries¹ and grain⁷. It often follows fishing fleets, feeding on discarded bycatch³. Breeding site The nest can be anything between a heap of grass, seaweed⁴, lichen, feathers (or other local materials)¹, and a simple sparsely-lined scrape⁴, that is usually positioned on open ground on a flat rock or a bare peat hag⁵. The species breeds in colonies, showing a preference for level-ground^{1, 9} that is well covered with fairly close, short vegetation^{5. 6}, often nesting under heather, bracken or other vegetation⁴ (sometimes under pine trees)¹. Suitable sites include flat, unbroken grassy slopes⁴, sand-dunes, the tops and ledges of coastal cliffs^{4, 5}, rocky offshore islands^{1, 5}, saltmarshes⁵, the margins of inland lakes^{2, 4}, islands in lakes and rivers², and high moorland^{4, 5}, although the species will also nest on buildings and rooftops¹.

Threats Some populations of this species have significantly declined due to decreasing food availability caused by competition and predation from Larus argentatus and Larus marinus^{1, 2, 8} and by changes in fishing and refuse disposal practices^{2, 5} (e.g. closure of landfill sites and the covering of waste)^{1, 2, 5, 8}. Population declines may also have been aided by poisoning from organochloride pollution¹¹ and contamination from pesticides². Colonies have been culled in Britain and Ireland in order to "protect" other breeding seabirds (e.g. terns) from predation and competition⁵. The species is exploited on its African wintering grounds¹, is hunted unsustainably in Denmark¹², and is threatened by egg-collecting and general human disturbance on the Iberian Peninsula⁸. Human disturbance occurs at wintering sites, caused by local people checking snare traps set to catch other species¹⁰. The species is susceptible to avian botulism, so may be threatened by future outbreaks of this disease⁵.

References 1. del Hoyo et al. (1996). 2. Olsen and Larsson (2003). 3. BirdLife International (2000). 4. Richards (1990). 5. Mitchell et al. (2004). 6. Snow and Perrins (1998). 7. Urban et al. (1986). 8. Barcena et al. (1984). 9. Hume and Pearson (1993). 10. Hario (2006). 11. Bustnes et al. (2006). 12. Bregnballe et al. (2006).

Further web sources of information

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

Text account compilers Stuart Butchart (BirdLife International), Rob Calvert (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2010) Species factsheet: Larus fuscus. Downloaded from http://www.birdlife.org on 30/7/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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