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LC
Whiskered Tern Chlidonias hybrida

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). The population trend appears to be fluctuating, 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.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls.
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Christidis, L.; Boles, W. E. 1994. The taxonomy and species of birds of Australia and its territories. Royal Australasian Ornithologists' Union, Melbourne.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Taxonomic note
Gender agreement of species name follows David and Gosselin (2002a).

Synonym(s)
Chlidonias hybridus Sibley and Monroe (1990, 1993), Chlidonias hybridus Cramp and Simmons (1977-1994), Chlidonias hybridus Dowsett and Forbes-Watson (1993), Chlidonias hybridus hybridus Christidis and Boles (1994), Chlidonias hybridus hybridus Cramp and Simmons (1977-1994), Chlidonias hybridus hybridus Dowsett and Forbes-Watson (1993), Chlidonias hybridus hybridus Sibley and Monroe (1990, 1993)

Population justification
The global population is estimated to number c.300,000-1,500,000 individuals (Wetlands International 2006), while national population estimates include: c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in China; c.50-10,000 wintering individuals in Taiwan; < c.1,000 individuals on migration in Korea; c.50-1,000 individuals on migration and < c.50 wintering individuals in Japan and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Russia (Brazil 2009).

Trend justification
The overall population trend is fluctuating, although some populations are stable and others have unknown trends (Wetlands International 2006).

Ecology
Behaviour Northern breeding populations of this species are fully migratory whilst tropical breeders are more nomadic or locally dispersive (del Hoyo et al. 1996). The species breeds from May to early-June (Richards 1990) in monospecific colonies of 10-100 pairs (del Hoyo et al. 1996). After breeding it departs for the wintering grounds from late-July to September, returning again between April and May (Richards 1990). The species sometimes forages singly, but is more common in small groups or larger mixed-species flocks on passage and in the winter (Snow and Perrins 1998). Habitat The species utilises a variety of wetland habitats but shows a preference for freshwater marshlands with scattered pools, particularly where the surrounding vegetation is grazed by cattle or horses (Richards 1990). It frequents inland lakes, rivers, marshes, temporary pans (e.g. in Africa), artificial fish-ponds and drainage-ponds covered with water-lilies (e.g. in Italy) (del Hoyo et al. 1996), swamps, river pools, reservoirs, large dams, sewage-ponds, flooded saltmarshes, arable fields (e.g. in Australia) (Higgins and Davies 1996, del Hoyo et al. 1996) and rice-fields (del Hoyo et al. 1996). In Australia the species also occurs along the coast on estuaries, coastal lagoons, creeks in mangrove swamps (Snow and Perrins 1998) and tidal mudflats (del Hoyo et al. 1996). Diet Its diet consists of terrestrial and aquatic insects (del Hoyo et al. 1996) (e.g. Dytiscidae, adult and larval Odonata, Orthoptera, flying ants (del Hoyo et al. 1996) and mosquitoes (Richards 1990)), spiders, frogs, tadpoles, small crabs (del Hoyo et al. 1996), shrimps (Richards 1990) and small fish (del Hoyo et al. 1996). Breeding site The nest is a heap of aquatic vegetation (Richards 1990, del Hoyo et al. 1996) or dry grass (del Hoyo et al. 1996), placed either on floating and emergent vegetation over water 60-80 cm deep or resting on the bottom of very shallow water (del Hoyo et al. 1996). The species nests in colonies, neighbouring pairs spaced between 1 and 5 m apart (del Hoyo et al. 1996), and may forage up to 9 km away from breeding sites (more usually within 1 km) (del Hoyo et al. 1996).

Threats
The species suffers nest destruction from the invasive rodent species Myocastor coypus in Italy (Arduin 1997). Utilisation Large numbers of eggs are collected for sale and local consumption in India (this may be causing population declines in some areas) (del Hoyo et al. 1996), and fishermen collect eggs in Ukraine (del Hoyo et al. 1996).

References
Arduin, M. 1997. The nutria problem. Informatore Agrario 53(29): 69-70.

Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

del Hoyo, J.; Elliott, A.; Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Higgins, P. J.; Davies, S. J. J. F. 1996. Handbook of Australian, New Zealand and Antarctic birds vol 3: snipe to pigeons. Oxford University Press, Oxford.

Richards, A. 1990. Seabirds of the northern hemisphere. Dragon's World Ltd, Limpsfield, U.K.

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

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

Text account compilers
Ekstrom, J., Butchart, S., Malpas, L.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Chlidonias hybrida. Downloaded from http://www.birdlife.org on 17/04/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/04/2014.

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.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Whiskered tern (Chlidonias hybrida) 0

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls and terns)
Species name author (Pallas, 1811)
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 10,000,000 km2
Country endemic? No
Links to further information
- Additional Information on this species
- Climate change species distributions