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LC
Common White Tern Gygis alba

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 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.

Taxonomic source(s)
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.
SACC. 2006. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.html#.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Distribution and population
The Common White Tern has a distribution across the tropics of the world, being found year-round on islands in the south Atlantic Ocean, the Indian Ocean, and the western and central Pacific. It is also a seasonal visitor to islands in the south-central and eastern Pacific off the coast of Mexico1.

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

Ecology
This species feeds mainly upon small fish, but will also take squid and crustaceans. The proportions vary locally, with 50% of its diet comprising of fish on Christmas Island compared to 85% on Hawaii. Prey are caught by diving. Its breeding season varies locally, nesting on coral islands, usually with vegetation, nesting in trees and bushes, on rocky slopes and cliffs, and also on artificial substrates. It lays a single egg on a bare branch, usually within a slight depression at a fork or on the midrib of a palm frond or banana leaf. It is resident year round on some islands though is a seasonal visitor on others where its non-breeding movements are not known (del Hoyo et al. 1996).

References
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.

Further web sources of information
Explore HBW Alive for further information on this species

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Ekstrom, J., Butchart, S., Calvert, R.

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

Recommended citation
BirdLife International (2014) Species factsheet: Gygis alba. Downloaded from http://www.birdlife.org on 28/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/08/2014.

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 - Common white tern (Gygis alba) 0

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls, Terns, Skimmers)
Species name author (Sparrman, 1786)
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 1,800 km2
Country endemic? No
Links to further information
- Additional Information on this species