Monday, July 30, 2007

Bridled tern fact sheet

Onychoprion anaethetus Bridled tern 

The Bridled tern is characterised by a long forked tail, brownish-grey coloured upper wings (hence the name “brown dorsal” in Portuguese) and a white ventral. On the front of the head between the eyes they have a white patch in the form of a triangle. The beak and legs are black, making them very easy to distinguish from other tern species sighted in the Azores. Males and females are alike (i.e. they are not sexually dimorphic). Bridled terns feed on fish which they catch by diving down. They form colonies on rocky islands to nest  in spring. The female lays only one egg in a small depression in the ground. The egg is then  incubated for about 28 days. Bridled terns are distributed throughout tropical and subtropical waters on islands of the Indian, Pacific and Atlantic Oceans. In the Azores they are considered a very rare migrant breeding species.

Length: 30 - 32 cm

Weight: 130 g

Wingspan: 77 - 81 cm

Population: c.10,000 mature individuals

Longevity: At least 20 years

Diet: Small fish and planktonic invertebrates

Eggs: 1

Incubation: 28 - 30 days

Nesting sites: Rugged areas or in small depressions

Fledging: 30 days

In other languages: 
Portuguese: Garajau de dorso castanho
Spanish: Charrán embridado
French: Sterne bridée
Italian: Sterna dalle redini
German: Zügelseeschawalbe
Dutch: Brilstern
Swedish: Tygeltärna
Norwegian: -
Danish: -
Finnish: Ohjasnokitiira

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