Ascension frigatebird

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Ascension frigatebird
Male Frigatebird with chick Fregata aquila.jpg
Male with chick at Boatswain Bird Island
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Fregatidae
Genus: Fregata
Species: F. aquila
Binomial name
Fregata aquila
(Linnaeus, 1758)
Juvenile

The Ascension frigatebird (Fregata aquila) is a seabird of the frigatebird family Fregatidae which breeds on the tiny Boatswain Bird Island just off Ascension Island in the tropical Atlantic Ocean.

The Ascension frigatebird is a large lightly built seabird with brownish-black plumage and a deeply forked tail. It has a wingspan of around 2 m (6.6 ft). The male has a striking red gular sac which it inflates to attract a mate. The female is slightly larger than the male and has a brown breast-band and sometimes a white belly. They feed on fish taken in flight from the ocean's surface (mostly flying fish), and sometimes indulge in kleptoparasitism, harassing other birds to force them regurgitate their food.

Taxonomy[edit]

The Ascension frigatebird was described by Linnaeus in 1758 in the 10th edition of his Systema Naturae under the binomial name Pelecanus aquilus.[2] His specimen had been collected from the Ascension Island by the Swedish explorer Pehr Osbeck.[3] The genus Fregata aquila formerly included all four species of large frigatebirds but in 1914 the Australian ornithologist Gregory Mathews split off the other three species leaving Fregata aquila to denote the Ascension frigatebird.[3] An analysis of ribosomal and mitochondrial DNA indicates that within the Fregata genus, the Ascension frigatebird is most closely related to the magnificent frigatebird.[4]

Distribution[edit]

The Ascension frigatebird formerly bred on Ascension Island itself, but the colonies were exterminated by feral cats introduced in 1815.[5] The birds nest on a 3 hectares (7.4 acres) plateau region on top of Boatswain Islet which lies 250 m (270 yd) off the northeast coast of Ascension Island.[5] A program conducted between 2002 and 2004 successfully eliminated all the feral cats[6] and as a result, in 2012 two pairs of frigatebirds returned to nest on Ascension Island.[7] In 2014 twelve nests were reported on Letterbox Peninsula at the extreme east end of the island.[8]

As with other frigatebirds, its movements outside the breeding season are little known because of identification problems within this difficult group, but it occurs off west Africa. It feeds on fish and similar surface prey such as small turtles.

A juvenile frigatebird found dying in 1953 in Tiree, Scotland was identified at the time as magnificent frigatebird but the specimen was re-examined in 2002 and found to be an Ascension frigatebird.[9] In July 2013 a juvenile was photographed at Bowmore on the island of Islay in Scotland.[10]

Description[edit]

The Ascension frigatebird is similar in size to the great frigatebird (Fregata minor) and the Christmas frigatebird (Fregata andrewsi). It measures 89–96 cm (35–38 in) in length, has a wingspan of 196–201 cm (77–79 in) and weighs around 1,250 g (2.76 lb).[11] The birds have a white axillary spur and juveniles show a white head, and a distinctly white hind neck with no reddish-brown hue. It has a brown breast band.

Status[edit]

A census of the Ascension frigatebird population on the islet of Boatswain conducted in 2001-2002 recorded around 6,250 breeding females implying a total population of 12,500 birds.[5] This number is similar to an earlier estimate of between 8,000 and 10,000 birds obtained in a study conducted in 1957-1959.[12] The species is classified as "Vulnerable" by the International Union for Conservation of Nature as it breeds on just a single tiny island.[1]

References[edit]

  1. ^ a b BirdLife International (2012). "Fregata aquila". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. (in Latin). Holmiae:Laurentii Salvii. p. 133. 
  3. ^ a b Mathews, GM (1914). "On the species and subspecies of the genus Fregata". Australian Avian Record 2 (6): 117–121. 
  4. ^ Kennedy, Martyn; Spencer, Hamish G (2004). "Phylogenies of the frigatebirds (Fregatidae) and tropicbirds (Phaethonidae), two divergent groups of the traditional order Pelecaniformes, inferred from mitochondrial DNA sequences". Molecular Phylogenetics and Evolution 31 (1): 31–38. doi:10.1016/j.ympev.2003.07.007. 
  5. ^ a b c Ratcliffe, Norman; Pelembe, Tara; White, Richard (2008). "Resolving the population status of Ascension Frigatebird Fregata aquila using a 'virtual ecologist' model". Ibis 150 (2): 300–306. doi:10.1111/j.1474-919X.2007.00778.x. 
  6. ^ Ratcliffe, Norman; Bella, Mike; Pelembe, Tara; Boyle, Dave; Benjamin, Raymond; White, Richard; Godley, Brendan; Stevenson, Jim; Sanders, Sarah (2010). "The eradication of feral cats from Ascension Island and its subsequent recolonization by seabirds". Oryx 44 (1): 20–29. doi:10.1017/S003060530999069X. 
  7. ^ McKie, Robin (8 December 2012). "Frigatebird returns to nest on Ascension for first time since Darwin". The Observer. Retrieved 10 December 2012. 
  8. ^ Fisher, Ian (23 January 2014). "Ascension frigatebird - the return continues". Royal Society for the Protection of Birds. Retrieved 8 December 2014. 
  9. ^ Walbridge, Grahame; Small, Brian; McGowan, Robert Y (2003). "From the Rarities Committee’s files: Ascension Frigatebird on Tiree – new to the Western Palearctic". British Birds 96 (2): 58–73. 
  10. ^ "Rare Ascension frigatebird recorded on Islay". BBC Highlands & Islands. 7 July 2013. Retrieved 11 July 2013. 
  11. ^ Orta, J; Christie, DA; Garcia, EFJ; Jutglar, F; Boesman, P. "Ascension Frigatebird (Fregata aquila)". In del Hoyo, J; Elliott, A; Sargatal, J; Christie, DA; de Juana, E. Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 30 November 2014. (subscription required)
  12. ^ Stonehouse, Bernard; Stonehouse, Sally (1963). "The frigatebird Fregata aquila of Ascension Island". Ibis 103b (3): 409–422. doi:10.1111/j.1474-919X.1963.tb06763.x. 

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