Bridled tern

Bridled tern
Adult on Lady Elliot Island, Australia
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Charadriiformes
Family:	Sternidae
Genus:	Onychoprion
Species:	O. anaethetus
Binomial name
Onychoprion anaethetus (Scopoli, 1786)
Synonyms
Sterna anaethetus Scopoli, 1786

The bridled tern (Onychoprion anaethetus, formerly Sterna anaethetus - see Bridge et al., 2005) is a seabird of the tern family Sternidae. It is a bird of the tropical oceans.

Description

In non-breeding plumage

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.

Breeding

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.

Lady Elliot Island, Qld, Australia

Various views and plumages

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  Bridled tern, at rookery

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  Juvenile on Lady Elliot Island, Queensland, Australia

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  In flight Lady Elliot Island, Queensland, Australia

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  Juveniles at Perth Zoo

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  Juvenile bathing at Perth Zoo

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  Juvenile or adult with non-breeding plumage taking off from a sea debris perch during Pelagic expedition off coast of Malpe

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  ID composite

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  Bridled Tern at Mumbai, Maharashtra, India.

References

1. BirdLife International (2012). "Sterna anaethetus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.

• Bridge, E. S.; Jones, A. W. & Baker, A. J. (2005): A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution. Molecular Phylogenetics and Evolution 35: 459–469. PDF fulltext
• Bull, John L.; Farrand, John Jr.; Rayfield, Susan & National Audubon Society (1977): The Audubon Society field guide to North American birds, Eastern Region. Alfred A. Knopf, New York. ISBN 0-394-41405-5
• Collinson, M. (2006). Splitting headaches? Recent taxonomic changes affecting the British and Western Palaearctic lists. British Birds 99(6): 306-323.
• Olsen, Klaus Malling & Larsson, Hans (1995): Terns of Europe and North America. Christopher Helm, London. ISBN 0-7136-4056-1
• Kasambe, R. Thakor, P., Dudhe, N. and Mane, P. (2014): Recent sighting records of

Bridled Tern Sterna anaethetus in Mumbai (Maharashtra) and Surat (Gujarat). Newsletter for Birdwatchers. 54(1): https://upload.wikimedia.org/wikipedia/commons/4/46/Bridled_Tern_Sterna_anaethetus_in_Mumbai_and_Surat.pdf

External links

• Avibase