Thai National Parks

Species of Thailand

Bridled tern

Onychoprion anaethetus, Giovanni Antonio Scopoli, 1786

(In Thai: นกนางนวลแกลบคิ้วขาว)

The bridled tern (Onychoprion anaethetus) is a seabird of the family Laridae. It is a bird of the tropical oceans. The scientific name is from Ancient Greek. The genus comes from meaning "claw" or "nail", and , meaning "saw". The specific anaethetus means "senseless, stupid".


This is a medium-sized tern, at 30–32 cm in length and with a 77–81 cm wingspan similar to the common tern in size, but more heavily built. The wings and deeply forked tail are long, and it has dark grey upperparts and white underparts. The forehead and eyebrows are white, as is a striking collar on the hindneck. It has black legs and bill. Juvenile bridled terns are scaly grey above and pale below.

This species is unlikely to be confused with any tern apart from the similarly dark-backed sooty tern and the spectacled tern from the Tropical Pacific. It is paler-backed than that sooty, (but not as pale as the grey-backed) and has a narrower white forehead and a pale neck collar.

Distribution and movements

This bird is migratory and dispersive, wintering more widely through the tropical oceans. It has markedly marine habits compared to most terns. The Atlantic subspecies melanopterus breeds in Mexico, the Caribbean and west Africa; other races occur around the Arabian Peninsula and in Southeast Asia and Australasia, but the exact number of valid subspecies is disputed. It is a rare vagrant to western Europe.

These are the four subspecies listed by the IOC:

  • O. a. melanopterus – (Swainson, 1837): Caribbean and West Africa.
  • O. a. antarcticus – (Lesson, 1831): Red Sea, Persian Gulf and western Indian Ocean.
  • O. a. anaethetus – (Scopoli, 1786): eastern Indian, and Pacific Oceans.
  • O. a. nelsoni – (Ridgway, 1919): west coast of Mexico and Central America.


This species breeds in colonies on rocky islands. It nests in a ground scrape or hole and lays one egg. It feeds by plunge-diving for fish in marine environments, but will also pick from the surface like the black tern and the gull-billed tern. It usually dives directly, and not from the "stepped-hover" favoured by the Arctic tern. The offering of fish by the male to the female is part of the courtship display.

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Category / Seasonal Status

BCST Category: Recorded in an apparently wild state within the last 50 years

BCST Seasonal status: Resident or presumed resident

Scientific classification

Onychoprion anaethetus

Common names

  • English: Bridled tern
  • French: Sterne bridée
  • Thai: นกนางนวลแกลบคิ้วขาว


  • Onychoprion anaethetus anaethetus, Scopoli, 1786

    Range: Eastern Indian, and Pacific Oceans.

  • Onychoprion anaethetus antarcticus, René Primevère Lesson, 1831

    Range: Red Sea, Persian Gulf and western Indian Ocean.

  • Onychoprion anaethetus melanopterus, William John Swainson, 1837

    Range: Caribbean and West Africa.

  • Onychoprion anaethetus nelsoni, Robert Ridgway, 1919

    Range: West coast of Mexico and Central America.


  • Onychoprion anaethetus subspecies anaethetus, Les Christidis & Walter E. Boles (2008)
  • Onychoprion anaethetus, AOU Checklist (1998)
  • Sterna anaethetus, Giovanni Antonio Scopoli (1786)

Conservation status

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)

Least Concern (BCST)

- LC: still widespread and numerous -

Range Map

Distribution map of Bridled tern, Onychoprion anaethetus in Thailand
  • Bangkok Coast
  • Chanthaburi Coast
  • Chumphon Coast
  • Hat Chao Mai National Park
  • Khao Laem Ya - Mu Ko Samet National Park
  • Khura Buri District, Phang Nga
  • Ko Lanta National Park
  • Ko Tao
  • Laem Pak Bia
  • Mueang Krabi District, Krabi
  • Mueang Phuket District, Phuket
  • Pak Thale
  • Phi Phi Islands
  • Samae San Island
  • Sathing Phra District, Songkhla
  • Similan Islands
  • Surin Islands
  • Takua Pa District, Phang Nga
  • Tarutao National Marine Park
  • Than Sadet - Koh Pha-Ngan National Park
  • Trat Coast
Range map of Onychoprion anaethetus in Thailand