Bridled Tern Onychoprion anaethetus


Taxonomic note
Onychoprion anaethetus (del Hoyo and Collar 2014) was previously placed in the genus Sterna.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: # _the_WP15.xls#.
Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
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: #
Turbott, E.G. 1990. Checklist of the Birds of New Zealand. Ornithological Society of New Zealand, Wellington.

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

Red List history
Year Category Criteria
2019 Least Concern
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 -
Extent of occurrence (EOO)

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 207,000,000 medium
Extent of Occurrence non-breeding (km2) 222,000,000 medium
Number of locations -
Fragmentation -
Population and trend
Estimate Data quality Derivation Year of estimate
No. of mature individuals 400000-1000000 poor estimated 2006
Population trend Unknown not applicable -
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 - - -
Largest subpopulations - - -
Generation length (yrs) 11.3 - - -

Population justification: The global population is estimated to number 610,000-1,500,000 individuals (Delany and Scott 2006). This roughly equates to 400,000-1,000,000 mature individuals. National population estimates include 100-10,000 breeding pairs and 50-1,000 individuals on migration in China; 10,000-1 million breeding pairs and > 1,000 individuals on migration in Taiwan (China) and < 100 breeding pairs and < 50 individuals on migration in Japan (Brazil 2009).

Trend justification: The overall population trend is uncertain, as some populations are decreasing, while others are increasing or have unknown trends (Delany and Scott 2006).

Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Anguilla (to UK) N Extant Yes
Antigua and Barbuda N Extant
Aruba (to Netherlands) N Extant
Australia N Extant Yes
Bahamas N Extant
Bahrain N Extant Yes
Barbados N Extant
Belize N Extant
Benin U Extant
Bermuda (to UK) N Extant Yes
Bonaire, Sint Eustatius and Saba (to Netherlands) N Extant
Brunei N Extant
Cambodia N Extant
Canada N Extant
Cayman Islands (to UK) N Extant
Chile V Extant
China (mainland) N Extant Yes
Christmas Island (to Australia) U Extant
Cocos (Keeling) Islands (to Australia) V Extant
Colombia N Extant
Comoros N Extant
Costa Rica N Extant Yes
Cuba N Extant
Curaçao (to Netherlands) N Extant
Denmark V Extant
Djibouti N Extant
Dominica N Extant
Dominican Republic N Extant
Ecuador N Extant Yes
Egypt N Extant
El Salvador N Extant
Equatorial Guinea N Extant
Eritrea N Extant
Fiji N Extant Yes
French Southern Territories U Extant
Gambia U Extant
Ghana V Extant
Greece V Extant
Grenada N Extant
Guadeloupe (to France) N Extant Yes
Guatemala U Extant
Guinea U Extant
Guinea-Bissau N Extant
Guyana N Extant
Haiti N Extant
Honduras N Extant
India N Extant
Indonesia N Extant
Iran, Islamic Republic of N Extant Yes
Iraq N Extant Yes
Israel N Extant
Jamaica N Extant Yes
Japan N Extant
Jordan N Extant Yes
Kenya N Extant
Kuwait N Extant Yes
Liberia V Extant
Madagascar N Extant
Malaysia N Extant
Maldives N Extant Yes
Martinique (to France) N Extant
Mauritania N Extant
Mauritius N Extant Yes
Mayotte (to France) U Extant
Mexico N Extant
Montserrat (to UK) N Extant
Mozambique N Extant
Myanmar U Extant
New Caledonia (to France) N Extant
New Zealand V Extant
Nicaragua N Extant
Nigeria N Extant
Oman N Extant Yes
Pakistan N Extant
Palau N Extant Yes
Panama N Extant
Papua New Guinea N Extant
Philippines N Extant
Puerto Rico (to USA) N Extant
Qatar N Extant Yes
Réunion (to France) U Extant
São Tomé e Príncipe N Extant
Saudi Arabia N Extant Yes
Senegal N Extant
Seychelles N Extant
Sierra Leone U Extant
Singapore N Extant
Sint Maarten (to Netherlands) N Extant Yes
Solomon Islands N Extant
Somalia N Extant Yes
South Africa N Extant
Sri Lanka N Extant
St Barthelemy (to France) N Extant
St Kitts and Nevis N Extant
St Lucia N Extant
St Martin (to France) N Extant Yes
St Vincent and the Grenadines N Extant
Sudan N Extant Yes
Taiwan, China N Extant Yes
Tanzania N Extant
Thailand N Extant
Timor-Leste N Extant Yes
Togo N Extant
Trinidad and Tobago N Extant
Turks and Caicos Islands (to UK) N Extant Yes
United Arab Emirates N Extant Yes Yes
United Kingdom V Extant
USA N Extant Yes
Vanuatu V Extant
Venezuela N Extant
Vietnam N Extant
Virgin Islands (to UK) N Extant Yes
Virgin Islands (to USA) N Extant Yes
Wallis and Futuna Islands (to France) N Extant Yes
Western Sahara N Extant Yes
Yemen N Extant Yes Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Anguilla (to UK) Dog Island
Anguilla (to UK) Sombrero Island
Aruba (to Netherlands) San Nicolas Bay Reef Islands
Australia Cape York to Cape Grenville Islands
Australia Higginson Island
Australia Houtman Abrolhos
Australia Lowendal Islands
Australia South Barnard Islands
Australia Stapleton Island
Australia Three Hummocks Island
Bahamas Booby Island
Bahamas Cay Lobos
Bahamas Cay Sal Marine Managenent Area
Bahamas Conception Island National Park
Bahamas Goulding Cay Wild Bird Reserve
Bahamas Graham's Harbour
Bahamas Great Isaac Cay
Bahamas Guana Cays
Bahamas Low Cay, High Cay and Sandy Hook
Bahamas North Atlantic Abaco Cays
Bahamas Peterson Cay (National Park)
Bahamas Samana Cay
Bahamas Tee Cay, Goat Cay and Long Rocks
China (mainland) Beiji Islands
China (mainland) Dongtou Islands
China (mainland) Nanji Islands Nature Reserve
China (mainland) Taizhou Islands
China (mainland) Wuyu Dao Island
China (mainland) Yushan Islands
China (mainland) Zhongjieshan Islands
Cuba Gran Humedal del Norte de Ciego de Ávila
Dominica L'llet
Dominica Point Des Foux
Dominican Republic Siete Hermanos Keys
Guadeloupe (to France) Falaises Nord et Îlet de Vieux-Fort de Marie-Galante
Guadeloupe (to France) Pointe des Châteaux
Indonesia Pulau Gunung Api
Indonesia Pulau Manuk
Iran, Islamic Republic of Nakhilu, Morghu and Ummal Karam islands
Iran, Islamic Republic of Sheedvar island
Jamaica Morant Cays and Bank
Jamaica Pedro Cays and Bank
Japan Yaeyama islands
Japan Yaeyama islands (Aragusukujima / Iriomotejima Islands) - Marine
Martinique (to France) Îlets et falaises de Sainte Anne
Martinique (to France) Rocher du Diamant
Mexico Islas Marietas
Nicaragua Farallones de Cosiguina
Nicaragua Farallones de Cosiguina - Marine
Oman Barr al Hikman
Oman Daymaniyat Islands
Oman Halaaniyaat Islands
Oman Masirah island
Oman Musandam islands
Panama Frailes del Sur Islands
Saudi Arabia Farasan Islands
Saudi Arabia Gulf coral islands
Saudi Arabia Gulf of Salwah
Saudi Arabia Tarut Bay
Somalia Jasiira Ceebaad and Jasiira Sacaada Diin
St Kitts and Nevis Booby Island
St Lucia Point Sables
Taiwan, China Cat Islet Seabird Refuge, Penghu County Refuge
Taiwan, China Matsu (Mazu) Islands Tern Refuge
Taiwan, China Northern Sea Islets
Trinidad and Tobago Little Tobago Island
Turks and Caicos Islands (to UK) Caicos Bank Southern Cays
Turks and Caicos Islands (to UK) Turks Bank Seabird Cays
United Arab Emirates Dayyinah Island (Diynah)
United Arab Emirates Qarnain Island
United Arab Emirates Sir Bu Na'air Island
United Arab Emirates Umm Amim
USA Dry Tortugas National Park
Virgin Islands (to USA) Saba Island and Cays

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Coastal/Supratidal Sea Cliffs and Rocky Offshore Islands suitable breeding
Marine Intertidal Rocky Shoreline suitable breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc major breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches major breeding
Marine Intertidal Tidepools suitable breeding
Marine Neritic Macroalgal/Kelp major breeding
Marine Neritic Macroalgal/Kelp major non-breeding
Marine Neritic Pelagic major breeding
Marine Neritic Pelagic major non-breeding
Marine Neritic Seagrass (Submerged) major breeding
Marine Neritic Seagrass (Submerged) major non-breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major non-breeding
Marine Neritic Subtidal Rock and Rocky Reefs major breeding
Marine Neritic Subtidal Rock and Rocky Reefs major non-breeding
Marine Neritic Subtidal Sandy major breeding
Marine Neritic Subtidal Sandy major non-breeding
Marine Neritic Subtidal Sandy-Mud major breeding
Marine Neritic Subtidal Sandy-Mud major non-breeding
Marine Oceanic Epipelagic (0-200m) suitable breeding
Marine Oceanic Epipelagic (0-200m) suitable non-breeding
Marine Oceanic Mesopelagic (200-1000m) suitable breeding
Marine Oceanic Mesopelagic (200-1000m) suitable non-breeding
Altitude 0 - 50 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Biological resource use Hunting & trapping terrestrial animals - Intentional use (species is the target) Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Reduced reproductive success, Species mortality
Human intrusions & disturbance Recreational activities Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Species disturbance

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

Recommended citation
BirdLife International (2020) Species factsheet: Onychoprion anaethetus. Downloaded from on 25/01/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from on 25/01/2020.