Forster's Tern Sterna forsteri


Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: # _the_WP15.xls#.
Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: #

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2018 Least Concern
2016 Least Concern
2012 Least Concern
2009 Least Concern
2008 Least Concern
2004 Least Concern
2000 Lower Risk/Least Concern
1994 Lower Risk/Least Concern
1988 Lower Risk/Least Concern
Species attributes

Migratory status full migrant Forest dependency Does not normally occur in forest
Land mass type Average mass 149 g

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 8,980,000 medium
Extent of Occurrence non-breeding (km2) 12,100,000 medium
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals poor estimated 2009
Population trend Increasing estimated -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations - - -
Percentage in largest subpopulation - - -
Generation length (yrs) 11 - - -

Population justification: The global population is estimated to number c.120,000 individuals.

Trend justification: In North America, this species has undergone a small or statistically insignificant increase over the last 40 years (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Antigua and Barbuda V Extant
Bahamas N Extant
Belize N Extant Yes Yes
Bermuda (to UK) N Extant
Brazil N Extant
Canada N Extant Yes Yes
Cayman Islands (to UK) N Extant
Costa Rica N Extant Yes
Cuba N Extant
Dominican Republic N Extant
El Salvador N Extant
Guadeloupe (to France) V Extant Yes
Guatemala N Extant
Haiti N Extant
Honduras N Extant
Iceland V Extant
Ireland V Extant
Jamaica V Extant
Mexico N Extant
Montserrat (to UK) V Extant
Netherlands V Extant
Nicaragua U Extant
Panama V Extant Yes
Portugal V Extant
Puerto Rico (to USA) N Extant
Spain V Extant
St Vincent and the Grenadines V Extant
Turks and Caicos Islands (to UK) N Extant
United Kingdom V Extant
USA N Extant Yes
Virgin Islands (to UK) V Extant
Virgin Islands (to USA) V Extant

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Canada Whitford and Rush Lakes
Canada Utikuma and Utikumasis Lakes
Canada Lesser Slave Lake PP
Canada Lakeland
Canada Creston Valley Wildlife Management Area
Canada Delta Marsh
Canada Netley-Libau Marsh
Canada Oak Hammock Marsh WMA
Canada Lake St. Martin Islands
Canada Marshy Point
Canada Riverton Sandy Bar
Canada Long Point Peninsula and Marshes
Canada Point Pelee
Canada Greater Rondeau Area
Canada Eastern Lake St. Clair
Canada Port Franks Forested Dunes
Canada Last Mountain Lake National Wildlife Area
Canada Paysen/Kettlehut Lake
Canada Blackstrap Coulee
St Vincent and the Grenadines Ashton Wetland
USA Ogden Bay UT03
USA Bear River Bay UT02
USA Barrier Island/Lagoon System
USA Barataria Terrebonne
Mexico Estero Santa Cruz
Mexico Estero Cardonal
Mexico Bahía Lechuguilla
Mexico Sistema Lagunario Huizache - Caimanero
Mexico Marismas Nacionales
Mexico Ensenada de Pabellones
Mexico Bahía Santa María
Mexico Bahía de Ceuta - Cospita

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Neritic Macroalgal/Kelp major non-breeding
Marine Neritic Macroalgal/Kelp major breeding
Marine Neritic Pelagic suitable non-breeding
Marine Neritic Seagrass (Submerged) major non-breeding
Marine Neritic Seagrass (Submerged) major breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major non-breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major breeding
Marine Neritic Subtidal Rock and Rocky Reefs major non-breeding
Marine Neritic Subtidal Rock and Rocky Reefs major breeding
Marine Neritic Subtidal Sandy major non-breeding
Marine Neritic Subtidal Sandy major breeding
Marine Neritic Subtidal Sandy-Mud major non-breeding
Marine Neritic Subtidal Sandy-Mud major breeding
Wetlands (inland) Permanent Freshwater Lakes (over 8ha) suitable breeding
Altitude 1000 - 2500 m Occasional altitudinal limits  

Purpose Primary form used Life stage used Source Scale Level Timing
Pets/display animals, horticulture - - International Non-trivial Recent

Recommended citation
BirdLife International (2022) Species factsheet: Sterna forsteri. Downloaded from on 16/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from on 16/08/2022.