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 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 Gmelin, 1789

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), SACC (2005 + updates), Sibley and Monroe (1990, 1993), Stotz et al. (1996), Turbott (1990)

Synonyms Gelochelidon nilotica Stotz et al. (1996), Gelochelidon nilotica Turbott (1990), Gelochelidon nilotica Christidis and Boles (2008), Gelochelidon nilotica Cramp and Simmons (1977-1994), Gelochelidon nilotica AOU checklist (1998 + supplements)

Taxonomic note The BirdLife Taxonomic Working Group is aware that phylogenetic analyses have been published which have proposed generic rearrangements which may affect this species, but prefers to wait until work by other taxonomists reveals how these changes affect the entire groups involved.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

150,000 - 420,000

unset

-

No

Range & population The Gull-billed tern breeds in warmer parts of the world in southern Europe, very small isolated population in northern Germany and Denmark, temperate and eastern Asia, both coasts of central and southern North America, the north-west and eastern coasts of South America and Australia. Post-breeding dispersal expands its range to include much of south Asia, Central America, New Zealand and parts of central 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 migratory, dispersing widely after breeding before travelling southwards to the wintering grounds¹. It breeds colonially in monospecific groups of 5-500 pairs (occasionally up to 1,000 pairs) or as solitary pairs amidst colonies of other species¹, remaining gregarious outside of the breeding season³. Habitat Breeding It breeds in a variety of locations with bare or sparsely vegetated islands, banks, flats, or spits of dry mud and sand⁴ including barrier beaches (shoals), dunes, saltmarshes, saltpans¹, freshwater lagoons^{1, 3}, estuaries, deltas³, inland lakes, rivers, marshes³ and swamps⁴. During this season it may also feed on emerging insects over lakes, agricultural fields, grasslands and even over semi-desert regions¹. Non-breeding On passage the species typically forages over saltpans, coastal lagoons, mudflats, marshes and wet fields¹, overwintering on estuaries, saltpans¹, lagoons³ and saltmarshes⁴ or in more inland sites such as large rivers, lakes, rice-fields³, sewage ponds, reservoirs, saltpans and irrigation canals⁴. Diet It is an opportunistic feeder and is largely insectivorous¹ taking adult and larval terrestrial and aquatic insects^{1, 2} (such as Ephemeroptera, Odonata, Lepidoptera and Coleoptera) as well as spiders, earthworms, small reptiles, frogs, small fish (6-9 cm long), aquatic invertebrates and rarely voles and small birds¹. Breeding site The nest is a scrape in dried mud, sand or gravel² on beaches, dry mudflats, dykes, sea-wrack on the tideline or on floating vegetation¹. Management information A conservation scheme for the protection of gull and tern breeding colonies in coastal lagoons and deltas (e.g. Po Delta, Italy) involves protection from human disturbance, prevention of erosion of islet complexes, habitat maintenance and the creation of new islets for nest sites⁵. The scheme particularly specifies that bare islets with 30-100 % cover of low vegetation (sward heights less than 20 cm) should be maintained or created as nesting sites⁵.

Threats The species is threatened by the deterioration and loss of habitat, e.g. through wetland drainage, agricultural intensification, pesticide pollution, fluctuating water levels¹, beach erosion and the development or modification of foraging sites⁶. It also suffers from reduced reproductive successes as a result of human disturbance at breeding colonies^{1, 6}.

References 1. del Hoyo et al. (1996). 2. Richards (1990). 3. Snow and Perrins (1998). 4. Higgins and Davies (1996). 5. Fasola and Canova (1996). 6. Molina and Erwin (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: Sterna nilotica. 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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