Thalasseus elegans 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Laridae

Scientific Name: Thalasseus elegans (Gambel, 1849)
Common Name(s):
English Elegant Tern
Spanish Charrán elegante, Gaviotín , Pagaza elegante
Sterna elegans Gambel, 1849
Thalasseus elegans Stotz et al. (1996)
Thalasseus elegans AOU checklist (1998 + supplements)
Taxonomic Source(s): SACC. 2005 and updates. A classification of the bird species of South America. Available at: #
Taxonomic Notes: Thalasseus elegans (del Hoyo and Collar 2014) was previously placed in the genus Sterna.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Keitt, B., Tershy, B. & Verlarde, E.
Facilitator/Compiler(s): Benstead, P., Butchart, S., Gilroy, J., Moreno, R., Sharpe, C.J., van der Merwe, N.
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.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Thalasseus 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.

Countries occurrence:
Chile; Colombia; Costa Rica; Ecuador; El Salvador; Mexico; Nicaragua; Panama; Peru; United States
Belgium; Denmark; Falkland Islands (Malvinas); France; Ireland; United States Minor Outlying Islands
Present - origin uncertain:
Guatemala; Honduras
Additional data:
Estimated area of occupancy (AOO) - km2:1300Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:240000
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
Upper elevation limit (metres):100
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: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).

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: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.

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):10.9
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): 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. Rodents were a problem until 2009. After successful rodent eradication, population increased up to 5 times (Samaniego-Herrera et al. 2011).

Conservation Actions [top]

Conservation Actions: 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.

Citation: BirdLife International. 2016. Thalasseus elegans. The IUCN Red List of Threatened Species 2016: e.T22694552A93457623. . Downloaded on 23 September 2018.
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