Species

Justification
This species is considered Near Threatened as it has a restricted breeding range, with more than 90% of the breeding population being restricted to a single island. It is also subject to large population fluctuations in response to climatic effects, and could be negatively affected by climate change, human intrusions and overfishing.

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.
SACC. 2006. A classification of the bird species of South America. Available at: http://www.museum.lsu.edu/~Remsen/SACCBaseline.html.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

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.

Synonym(s)
Thalasseus elegans Stotz et al. (1996), Thalasseus elegans AOU checklist (1998 + supplements), Thalasseus elegans , Thalasseus elegans elegans Stotz et al. (1996)

Distribution and population
Sterna elegans breeds along the Pacific coast from south California, USA, to Baja California and the Gulf of California, Mexico (Howell and Webb 1995a, AOU 1998). The estimated population is 51,000-90,000 individuals (J. A. Kushlan et al. 2002) with up to 95% breeding on Isla Rasa in the Gulf of California (Velarde and Anderson 1994). At least three other Mexican islands are used at least occasionally (Velarde and Anderson 1994). In addition, small populations breed on Bolsa Chica (50-4,000 pairs, first recorded in 1987) and in San Diego bay (500-800 pairs), California (Velarde and Anderson 1994, Gochfeld and Burger 1996, E. Verlarde in litt. 1998, B. Tershy and B. Keitt in litt. 1999). Non-breeding birds summer from California to Costa Rica (AOU 1998). Birds winter from Guatemala to El Salvador, Nicaragua, Costa Rica, Panama, Colombia, Ecuador, Peru and Chile (AOU 1998). There are significant population fluctuations, probably caused by the effects of El Niño Southern Oscillation (compounded by over-fishing) on prey abundance and consequently breeding success (E. Verlarde in litt. 1998, B. Tershy and B. Keitt in litt. 1999). Only the Isla Rasa colony breeds every year (B. Tershy and B. Keitt in litt. 1999), but fluctuations are considerably less than one order of magnitude.

Population justification
Kushlan et al. (2002).

Trend justification
The population is suspected to undergo dramatic fluctuations in response to El Niño Southern Oscillation events and subsequent fluctuations in fish populations (Velarde and Anderson 1994, B. Tershy and B. Keitt in litt. 1999).

Ecology
This species breeds on flat rocky areas and is strongly tied to the coast. It forages in inshore waters, estuarine habitats, salt ponds and lagoons, with some individuals venturing further offshore in the non-breeding season.

Threats
Population fluctuations may be related to El Niño Southern Oscillation events, but food supply may also be influenced by over-fishing. Nest robbery formerly reduced colony size on Isla Rasa, but this site now receives adequate protection.

Conservation actions underway
None is known.

Conservation actions proposed
Monitor population trends throughout the breeding range. Research links between climate, fisheries, prey availability and breeding success. Ensure continued effective protection of all breeding colonies.

References
Anderson, D. W. 1976. The Gulf of California, Mexico. Canadian Field-Naturalist 90: 270-271.

Sowls, A. L.; DeGange, A. R.; Nelson, J. W.; Lester, G. S. 1980. Catalogue of California seabird colonies. US Fish and Wildlife Service, US Department of the Interior, Washington, D.C.

Gochfeld, M.; Burger, J. 1996. Sternidae (Terns). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 624-667. Lynx Edicions, Barcelona, Spain.

Velarde, E.; Anderson, D. W. 1994. Conservation and management of seabird islands in the Gulf of California: setbacks and successes. In: Nettleship, D.N.; Burger, J.; Gochfeld, M. (ed.), Seabirds on islands: threats, case studies and action plans, pp. 229-243. BirdLife International, Cambridge, UK.

Howell, S. N. G.; Webb, S. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford.

AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.

Kushlan, J. A.; Steinkamp, M. J.; Parsons, K. C.; Capp, J.; Cruz, M. A.; Coulter, M.; Davidson, I.; Dickson, L.; Edelson, N.; Ellio, R.; Erwin, M.; Hatch, S.; Kress, S.; Milko, R.; Miller, S.; Mills, K.;…authors continued in notes. 2002. Waterbird conservation for the Americas. U.S. Fish & Wildlife Service National Publications Clearinghouse, Shepherdstown, U.S.A.

Further web sources of information
View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Benstead, P., Butchart, S., Gilroy, J., Sharpe, C J

Contributors
Keitt, B., Tershy, B., Verlarde, E.

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

Recommended citation
BirdLife International (2013) Species factsheet: Sterna elegans. Downloaded from http://www.birdlife.org on 22/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2013.

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

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