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South American Tern Sterna hirundinacea
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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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to 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)
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: #

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

Distribution and population
This species breeds on the coasts of southern Peru and Espírito Santo, east-central Brazil south to Tierra del Fuego, Argentina and Chile, and the Falkland Islands (Malvinas) (Duffy et al. 1984, Schlatter 1984, Woods 1988, De Tarso Zuquim Antas 1991). In the austral winter, most birds breeding in the extreme south move north to Uruguay (where breeding remains unconfirmed), and the species also winters north to Ecuador and Bahia, Brazil (Antas 1991). There are also large colonies on inshore islands in Guanabara Bay and off the Espírito Santo coast, Brazil (Antas 1991). The population on the Falkland Islands was recently estimated at 6,000-12,000 pairs (Woods and Woods 1997), and a colony exceeding 1,000 pairs was discovered in south Peru in 1995 (del Hoyo et al. 1996), where it is fairly common (Clements and Shany 2001). However, although formerly locally common in Chile, only two breeding sites are now known (Damas Island and Inutil Bay near Porvenir), and extensive searches to locate former colonies between 1994 and 1997 were unsuccessful (Mickstein in litt. 1998).

Trend justification
The population is suspected to be in decline owing to disturbance of its nesting sites (del Hoyo et al. 1996).

The species is almost exclusively coastal, breeding on rocky or sandy beaches, cliff tops and small islands. Non-breeders frequent coastal waters, beaches, estuaries and harbours. It feeds mainly on small fish and crustaceans and probably also takes insects. Laying occurs in April-June in Brazil, early November in north Argentina and early December in south Argentina. Two to three eggs are laid (del Hoyo et al. 1996).

Tourism may be responsible for the decline of the Chilean population, with a breeding colony at Lake Calafquen apparently deserted due to disturbance from bathing tourists and water bikes (Mickstein in litt. 1998). Tourism has also increased markedly on the Argentinean coast, and this has presumably had a detrimental effect on at least some breeding colonies (del Hoyo et al. 1996). Egg collecting is also a problem at colonies in Espírito Santo, Brazil (Antas 1991), and may have contributed to the decline of the Chilean population (Mickstein in litt. 1998). Commercial fishing and industry are considered potential threats to the Falkland Islands population (Woods and Woods 1997).

Antas, P. T. Z. 1991. Status and conservation of seabirds breeding in Brazilian waters. In: Croxall, J.P. (ed.), Seabird status and conservation: a supplement, pp. 141-158. International Council for Bird Preservation, Cambridge, U.K.

Clements, J. F.; Shany, N. 2001. A field guide to the birds of Peru. Lynx Edicions, Barcelona, Spain.

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.

Duffy, D. C.; Hays, C.; Plenge, M. A. 1984. The conservation status of Peruvian seabirds. In: Croxall, J.P.; Evans, P.G.H.; Schreiber, R.W. (ed.), Status and conservation of the world's seabirds, pp. 245-259. International Council for Bird Preservation, Cambridge, UK.

Schlatter, R. P. 1984. The status and conservation of seabirds in Chile. In: Croxall, J.P.; Evans, P.G.H.; Schreiber, R.W. (ed.), Status and conservation of the world's seabirds, pp. 261-269. International Council for Bird Preservation, Cambridge, U.K.

Woods, R. W. 1988. Guide to birds of the Falkland Islands. Anthony Nelson, Oswestry, U.K.

Woods, R. W.; Woods, A. 1997. Atlas of breeding birds of the Falkland Islands. Anthony Nelson, Oswestry, U.K.

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

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

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

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

Recommended citation
BirdLife International (2016) Species factsheet: Sterna hirundinacea. Downloaded from on 25/10/2016. Recommended citation for factsheets for more than one species: BirdLife International (2016) IUCN Red List for birds. Downloaded from on 25/10/2016.

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 - South American tern (Sterna hirundinacea) 0

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls, Terns, Skimmers)
Species name author Lesson, 1831
Population size mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 1,410,000 km2
Country endemic? No
Links to further information
- Additional Information on this species