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Bridled Tern | Onychoprion anaethetus
Brilstern | Charrán embridado
The Bridled Tern is a slim marine tern with a dark cap, grey-brown back and white supercilium. It breeds in small, loose colonies on rocky islets and cays scattered across the region. At sea it often rests on floating sargassum, driftwood and buoys, unlike Sooty Tern, which hardly ever settles on water or floating objects.
Voice
A barking, yapping wep-wep and a rising, whining wup-weeeuw, mainly at the colony; mostly silent at sea.
Recording: David Darrell-Lambert — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
35–38 cm, with long, narrow wings and a deeply forked tail with long white outer tail feathers. The cap is black; the narrow white forehead extends as a supercilium behind the eye, and a black loral stripe runs to the bill. A pale band across the hindneck separates the cap from the grey-brown back and wings. Underparts white; the underwing is mostly white with dark primary tips. Bill and legs black. The sexes are alike. Juveniles have pale fringes above, a streaked crown and white underparts.
Confusion species
Sooty Tern Onychoprion fuscatus is larger, with a black back that does not contrast with the cap, no white collar, a broader white forehead patch that does not extend behind the eye and a darker underwing; juvenile Sooty Terns are largely dark. Sandwich Tern Thalasseus sandvicensis and Common Tern Sterna hirundo are pale grey above.
Habitat
Open sea and coastal waters, often over reefs and along drifting sargassum mats. It breeds on rocky islets, cliffs and coral cays, scattered or in loose colonies; the single egg is laid in shelter, in a rock crevice, under an overhang or beneath low vegetation.
Where the bird is most at home, classified by the vegetation types of the Caribbean.
Range and movements
Breeds widely throughout the region, including the Bahamas, the Turks and Caicos Islands, cays off Cuba, Hispaniola and Puerto Rico, the Virgin Islands, many small islands of the Lesser Antilles south to the Grenadines, off Aruba, Bonaire and Curaçao, and off Tobago. On the large islands mainly seen offshore. Beyond the region in the tropical Atlantic to West Africa, the Red Sea, the Indian Ocean and the western Pacific.
- Summer visitor (c. Oct–Mar)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
In the breeding season it can be seen from boats along rocky islets, where birds often pass close or perch on rocks. At sea, checking terns perched on floating sargassum and driftwood is worthwhile.
Conservation status
Not threatened. The world population is large. Because its nests are scattered in rock crevices, it is less vulnerable to egg collecting than Sooty Tern, but introduced rats and cats and disturbance on breeding islands are local threats.
Scientific name
Onychoprion anaethetus | (Scopoli, 1786)
Scopoli described the species in 1786 as Sterna Anaethetus; because it was later moved to another genus, the author and year stand in brackets. The genus Onychoprion was introduced in 1832 by Wagler. Onychoprion comes from Greek onux 'nail, claw' and prion 'saw'. anaethetus goes back to Greek anaisthētos and means 'senseless, stupid'. The specimen the first description was based on came from Panay, Philippines.