Justification This species has an extremely 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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely 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, 1766

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

Synonyms Chroicocephalus ridibundus Christidis and Boles (2008)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

4,800,000 - 8,900,000

unset

-

No

Range & population The Black-headed Gull breeds in north-east North America and across much of Europe and Asia, excluding the north of each continent (northern Scandinavia and north Russia), and south Asia. Some populations in North America and the milder areas of Europe are resident, with the remaining populations wintering to the south over a large range, encompassing much of the southern coast of Asia and Europe, and the central and northern coast of Africa¹.

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

Ecology: Behaviour Northern breeding populations of this species are strongly migratory although populations at lower latitudes tend to be sedentary or locally dispersive¹. The species breeds between April and May¹ in dense colonies of up to several thousand pairs^{1, 4} often with other gull or tern species³. It generally remains gregarious throughout the year⁴ and may roost in large flocks during the winter². Habitat Breeding The species chiefly breeds inland and shows a preference for shallow, calm⁴, temporarily flooded wetland habitats¹ with lush vegetation^{1, 3}. It forms nesting colonies on the margins of lakes^{1, 2, 3}, lagoons^{3, 4}, slow-flowing rivers, deltas, estuaries⁴ and on tussocky marshes^{1, 2, 3}, but may also nest on the upper zones of saltmarshes^{1, 4}, coastal dunes and offshore islands in more coastal areas¹. The species will also utilise artificial sites such as sewage ponds, gravel- and clay-pits, ponds, canals and floodlands⁴ and may nest on the dry ground of heather moors, sand-dunes, beaches^{1, 4} and stony islets⁴. Non-breeding During the winter the species is most common in coastal habitats¹ and tidal inshore waters, showing a preference for inlets or estuaries with sandy or muddy beaches, and generally avoiding rocky or exposed coastlines⁴. It may also occur inland during this season, frequenting ploughed fields, moist grasslands, urban parks, sewage farms, refuse tips, reservoirs, ponds and ornamental waters⁴, and roosts on sandy and gravel sites or on inland reservoirs². Diet Its diet consists predominantly of aquatic and terrestrial insects, earthworms and marine invertebrates (e.g. molluscs, crustaceans and marine worms)¹ although it may also take fish¹ (usually dead or sick)³, rodents (e.g. voles)³ and agricultural grain¹. During the non-breeding season the species may rely heavily on artificial food sources provided by man, especially in Western Europe¹, and often scavenges from refuse tips during this period². Breeding site The nest is a rough construction of vegetation² based on a shallow scrape⁴ and placed on a floating mat, in broken reeds, on a hummock, or sometimes on dry, grassy or sandy ground^{1, 3}. The species shows a strong preference for nesting near vegetation (although vegetation overgrowth can lead to the desertion of colony sites)¹. It usually nests in dense colonies with neighbouring nests placed an average of 1 m apart¹.

Threats The species is susceptible to avian influenza⁵ and avian botulism so may be threatened by future outbreaks of these diseases⁶. It may also be threatened by future coastal oil spills⁷ and has suffered local population declines in the past as a result of egg collecting¹. In some areas of its breeding range the species may also suffer from reduced reproductive successes due to contamination with chemical pollutants¹.

References 1. del Hoyo et al. (1996). 2. Richards (1990). 3. Flint et al. (1984). 4. Snow and Perrins (1998). 5. Melville and Shortridge (2006). 6. Hubalek et al. (2005). 7. Gorski et al. (1977).

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 ridibundus. Downloaded from http://www.birdlife.org on 6/9/2010

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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