Sterna trudeaui


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Sterna trudeaui
Species Authority: Audubon, 1838
Common Name(s):
English Snowy-crowned Tern
Taxonomic Notes: 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.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Facilitator/Compiler(s): Ekstrom, J., Butchart, S., Harding, M., Calvert, R.
This species has a very 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 may be small, 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.

Geographic Range [top]

Range Description: This species breeds in south-east Brazil and Uruguay, through to Patagonia, though rarely Santa Cruz, Argentina, and in Chile (from Aconcaqua to Llanquihue). In winter, the species moves north as far as southern Peru on the west coast, and Rio de Janiero, Brazil, on the east coast (del Hoyo et al. 1996).
Argentina; Brazil; Chile; Uruguay
Falkland Islands (Malvinas); Paraguay
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The population is estimated to number 1,000-10,000 individuals, roughly equating to 670-6,700 mature individuals.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: This species frequents fresh and saline wetlands, both coastal and inland. Its diet includes small fish and insects, feeding mainly on pejerrey in Chile. It forages over shallow clear waters on the edge of lagoons, rivers and estuaries, pluynge-diving for fish. It will also feed on plouged fields. Breeding appears to occur from October to December on vegetated lagoons, mainly in marhses but also on dykes and islands in saline lagoons. Adults will vigorously attack and even strike intruders (del Hoyo et al. 1996).
Systems: Terrestrial; Freshwater; Marine

Threats [top]

Major Threat(s): The species only nests in large wetlands, suggesting habitat loss may be a potentially serious problem (del Hoyo et al. 1996).

Citation: BirdLife International 2012. Sterna trudeaui. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 04 September 2015.
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