Thalasseus bergii 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Laridae

Scientific Name: Thalasseus bergii (Lichtenstein, 1823)
Common Name(s):
English Greater Crested Tern, Crested Tern, Great Crested-Tern, Greater Crested Tern, Swift Tern
French Sterne huppée
Sterna bergii Lichtenstein, 1823
Thalasseus bergii AOU checklist (1998 + supplements)
Thalasseus bergii Christidis and Boles (2008)
Taxonomic Source(s): Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Taxonomic Notes: Thalasseus bergii (del Hoyo and Collar 2014) was previously placed in the genus Sterna.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Facilitator/Compiler(s): Butchart, S., Calvert, R., Ekstrom, J., Malpas, L. & Ashpole, J
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). The population trend appears to be stable, 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.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species can be found found on islands and coastlines of the tropical and subtropical Old World, ranging from the Atlantic Coast of South Africa, south around the Cape and continuing along the coast of Africa and Asia almost without break to south-east Asia and Australia. It can also be found on Madagascar, islands of the western Indian ocean and islands of the western and central Pacific Ocean. Outside the breeding season it can be found at sea throughout this range, with the exception of the central Indian Ocean (del Hoyo et al. 1996).
Countries occurrence:
Australia; Bahrain; Bangladesh; British Indian Ocean Territory; Brunei Darussalam; Cambodia; China; Cook Islands; Djibouti; Egypt; Eritrea; Fiji; French Polynesia; Guam; India; Indonesia; Iran, Islamic Republic of; Iraq; Israel; Japan; Kenya; Kiribati; Kuwait; Madagascar; Malaysia; Maldives; Marshall Islands; Mauritius; Mayotte; Micronesia, Federated States of ; Mozambique; Myanmar; Namibia; New Caledonia; Northern Mariana Islands; Oman; Pakistan; Palau; Papua New Guinea; Philippines; Qatar; Saudi Arabia; Seychelles; Singapore; Solomon Islands; Somalia; South Africa; Sri Lanka; Sudan; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Tonga; Tuvalu; United Arab Emirates; Vanuatu; Viet Nam; Wallis and Futuna; Yemen
Jordan; Korea, Democratic People's Republic of; Nauru; New Zealand; United States
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:142000000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The global population is estimated to number c.150,000-1,100,000 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.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Taiwan and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Japan (Brazil 2009).

Trend Justification:  The overall population trend is stable, although some populations have unknown trends (Wetlands International 2006).
Current Population Trend:Stable
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:Behaviour Many populations of this species remain sedentary in their breeding areas or disperse locally (del Hoyo et al. 1996) although some are more migratory (Urban et al. 1986). The species breeds in large dense colonies, or in small groups of less than 10 pairs amidst colonies of other species (e.g. King Gull Larus hartlaubii or Silver Gull Larus novaehollandiae) (del Hoyo et al. 1996). It usually forages singly (Urban et al. 1986) or in small groups (del Hoyo et al. 1996) but several hundred individuals may gather at roost sites (Langrand 1990). Habitat The species inhabits tropical and subtropical coastlines, foraging in the shallow waters of lagoons (Higgins and Davies 1996, del Hoyo et al. 1996), coral reefs (del Hoyo et al. 1996), estuaries (Urban et al. 1986, del Hoyo et al. 1996), bays, harbours and inlets (Higgins and Davies 1996), along sandy, rocky, coral (del Hoyo et al. 1996) or muddy shores, on rocky outcrops in open sea, in mangrove swamps (Langrand 1990) and also far out to sea on open water (del Hoyo et al. 1996). It shows a preference for nesting on offshore islands (Urban et al. 1986, del Hoyo et al. 1996), low-lying coral reefs, sandy or rocky coastal islets, coastal spits, lagoon mudflats (del Hoyo et al. 1996), and artificial islets in saltpans and sewage works (Urban et al. 1986, del Hoyo et al. 1996) within 3 km of the coast (del Hoyo et al. 1996). Diet Its diet consists predominantly of pelagic fish 10-50 cm long (Urban et al. 1986, del Hoyo et al. 1996) although it will also take cephalopods (e.g. squid), crustaceans (del Hoyo et al. 1996) (e.g. crabs (del Hoyo et al. 1996) and prawns (Higgins and Davies 1996)), insects and hatchling turtles opportunistically (del Hoyo et al. 1996). Breeding site The nest is a shallow scrape in bare sand, rock or coral (del Hoyo et al. 1996) in flat open sites (Urban et al. 1986) on offshore islands (Urban et al. 1986, del Hoyo et al. 1996), low-lying coral reefs, sandy or rocky coastal islets, coastal spits, lagoon mudflats (del Hoyo et al. 1996) or islets in saltpans and sewage works (Urban et al. 1986, del Hoyo et al. 1996). The species nests in dense colonies (Urban et al. 1986) with neighbouring nests very close together (rims may be touching) (del Hoyo et al. 1996), and usually forages within 3 km of the breeding colony (del Hoyo et al. 1996).
Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):10.5
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): The species is vulnerable to human disturbance (e.g. tourism) at breeding colonies on offshore islands (Benoit and Bretagnolle 2002) which can lead to nest desertion and increased predation of eggs and nestlings by gulls and ibises (Cooper et al. 1990). The species is also threatened by injury and mortality from entanglement with baited hooks, fishing lines, nets and human refuse (e.g. plastic bags) (Cooper et al. 1990). Utilisation Most breeding colonies of this species are subject to subsistence egg collecting (de Korte 1991, del Hoyo et al. 1996).

Citation: BirdLife International. 2016. Thalasseus bergii. The IUCN Red List of Threatened Species 2016: e.T22694571A93458063. . Downloaded on 22 September 2018.
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