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Sterna nilotica

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES CHARADRIIFORMES LARIDAE

Scientific Name: Sterna nilotica
Species Authority: Gmelin, 1789
Common Name/s:
English Gull-billed Tern
French Sterne hansel
Synonym/s:
Gelochelidon nilotica AOU checklist (1998 + supplements)
Gelochelidon nilotica nilotica Christidis and Boles (2008)
Gelochelidon nilotica nilotica Stotz et al. (1996)
Gelochelidon nilotica nilotica Cramp and Simmons (1977-1994)
Gelochelidon nilotica nilotica Turbott (1990)
Taxonomic Notes: 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.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor/s: BirdLife International
Reviewer/s: Butchart, S. & Symes, A.
Facilitator/s: Butchart, S., Ekstrom, J., Calvert, R., Malpas, L.
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.

Geographic Range [top]

Range Description: 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 Africa (del Hoyo et al. 1996).
Countries:
Native:
Afghanistan; Albania; Algeria; Antigua and Barbuda; Argentina; Armenia (Armenia); Aruba; Australia; Austria; Azerbaijan; Bahamas; Bahrain; Bangladesh; Barbados; Belize; Benin; Bonaire, Sint Eustatius and Saba; Brazil; Brunei Darussalam; Bulgaria; Burkina Faso; Burundi; Cambodia; Cameroon; Canada; Cayman Islands; Chad; China; Colombia; Congo, The Democratic Republic of the; Costa Rica; Côte d'Ivoire; Cuba; Curaçao; Cyprus; Czech Republic; Denmark; Djibouti; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Eritrea; Ethiopia; France; French Guiana; Gambia; Germany; Ghana; Gibraltar; Greece; Guadeloupe; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; India; Indonesia; Iran, Islamic Republic of; Iraq; Israel; Italy; Japan; Jordan; Kazakhstan; Kenya; Kuwait; Kyrgyzstan; Liberia; Libya; Macedonia, the former Yugoslav Republic of; Malawi; Malaysia; Maldives; Mali; Malta; Martinique; Mauritania; Mexico; Moldova; Mongolia; Montserrat; Morocco; Myanmar; Nepal; New Zealand; Nicaragua; Niger; Nigeria; Oman; Pakistan; Palestinian Territory, Occupied; Panama; Paraguay; Peru; Philippines; Portugal; Puerto Rico; Qatar; Romania; Rwanda; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Saudi Arabia; Senegal; Sierra Leone; Singapore; Sint Maarten (Dutch part); Somalia; South Sudan; Spain; Sri Lanka; Sudan; Suriname; Switzerland; Syrian Arab Republic; Taiwan, Province of China; Tajikistan; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Trinidad and Tobago; Tunisia; Turkey; Turkmenistan; Turks and Caicos Islands; Uganda; Ukraine; United Arab Emirates; United States; Uruguay; Uzbekistan; Venezuela, Bolivarian Republic of; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Western Sahara; Yemen; Zambia
Vagrant:
Angola (Angola); Belgium; Bermuda; Bosnia and Herzegovina; Botswana; Comoros; Croatia; Finland; Gabon; Guam; Hungary; Ireland; Jamaica; Korea, Republic of; Lebanon; Luxembourg; Montenegro; Norway; Poland; Saint Martin (French part); Serbia (Serbia); Seychelles; Slovakia; Slovenia; South Africa; Sweden; United Kingdom; Zimbabwe
Present - origin uncertain:
Anguilla; Northern Mariana Islands; Papua New Guinea
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The global population is estimated to number c.150,000-420,000 individuals (Wetlands International 2006), while national population estimates include: c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in China; c.50-1,000 individuals on migration and < c.50 wintering individuals in Taiwan and < c.1,000 individuals on migration in Japan (Brazil 2009).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Behaviour Northern breeding populations of this species are migratory, dispersing widely after breeding before travelling southwards to the wintering grounds (del Hoyo et al. 1996). It breeds colonially in monospecific groups of 5-500 pairs (occasionally up to 1,000 pairs) or as solitary pairs amidst colonies of other species (del Hoyo et al. 1996), remaining gregarious outside of the breeding season (Snow and Perrins 1998). Habitat Breeding It breeds in a variety of locations with bare or sparsely vegetated islands, banks, flats, or spits of dry mud and sand (Higgins and Davies 1996) including barrier beaches (shoals), dunes, saltmarshes, saltpans (del Hoyo et al. 1996), freshwater lagoons (del Hoyo et al. 1996, Snow and Perrins 1998), estuaries, deltas (Snow and Perrins 1998), inland lakes, rivers, marshes (Snow and Perrins 1998) and swamps (Higgins and Davies 1996). During this season it may also feed on emerging insects over lakes, agricultural fields, grasslands and even over semi-desert regions (del Hoyo et al. 1996). Non-breeding On passage the species typically forages over saltpans, coastal lagoons, mudflats, marshes and wet fields (del Hoyo et al. 1996), overwintering on estuaries, saltpans (del Hoyo et al. 1996), lagoons (Snow and Perrins 1998) and saltmarshes (Higgins and Davies 1996) or in more inland sites such as large rivers, lakes, rice-fields (Snow and Perrins 1998), sewage ponds, reservoirs, saltpans and irrigation canals (Higgins and Davies 1996). Diet It is an opportunistic feeder and is largely insectivorous (del Hoyo et al. 1996) taking adult and larval terrestrial and aquatic insects (Richards 1990, del Hoyo et al. 1996) (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 birds (del Hoyo et al. 1996). Breeding site The nest is a scrape in dried mud, sand or gravel (Richards 1990) on beaches, dry mudflats, dykes, sea-wrack on the tideline or on floating vegetation (del Hoyo et al. 1996). 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 sites (Fasola and Canova 1996). 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 sites (Fasola and Canova 1996).
Systems: Terrestrial; Freshwater; Marine

Threats [top]

Major Threat(s): The species is threatened by the deterioration and loss of habitat, e.g. through wetland drainage, agricultural intensification, pesticide pollution, fluctuating water levels (del Hoyo et al. 1996), beach erosion and the development or modification of foraging sites (Molina and Erwin 2006). It also suffers from reduced reproductive successes as a result of human disturbance at breeding colonies (del Hoyo et al. 1996, Molina and Erwin 2006).
Citation: BirdLife International 2012. Sterna nilotica. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 24 April 2014.
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