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The lesser frigatebird (''Fregata ariel'') is a seabird of the frigatebird family
Fregatidae Frigatebirds are a Family (biology), family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, l ...
. At around 75 cm (30 in) in length, it is the smallest species of frigatebird. It occurs over tropical and subtropical waters across the Indian and Pacific Oceans as well as off the Atlantic coast of Brazil. The lesser frigatebird is a lightly built seabird with brownish-black plumage, long narrow wings and a deeply forked tail. The male has a striking red gular sac which he inflates to attract a mate. The female is slightly larger than the male and has a white breast and belly. Frigatebirds feed on fish taken in flight from the ocean's surface (often
flying fish The Exocoetidae are a family (biology), family of Saltwater fish, marine Actinopterygii, ray-finned fish in the order (biology), order Beloniformes, known colloquially as flying fish or flying cod. About 64 species are grouped in seven genus, ge ...
), and sometimes indulge in
kleptoparasitism Kleptoparasitism (originally spelt clepto-parasitism, meaning "parasitism by theft") is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct f ...
, harassing other birds to force them to regurgitate their food.


Taxonomy

The lesser frigatebird was first described as ''Atagen ariel'' by the English zoologist George Gray in 1845 from a specimen collected on
Raine Island Raine Island is a vegetated coral cay in total area situated on the outer edges of the Great Barrier Reef off northeastern Australia. It lies approximately north-northwest of Cairns, Queensland, Cairns in Queensland, about east-northeast of C ...
,
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
, Australia. The lesser frigatebird is one of five closely related species of the genus ''Fregata''. The other four are: the
great frigatebird The great frigatebird (''Fregata minor'') is a large seabird in the frigatebird family (biology), family. There are major nesting populations in the tropical Pacific Ocean, such as Hawaii and the Galápagos Islands; in the Indian Ocean, colonies ...
(''Fregata minor''), the Christmas frigatebird (''Fregata andrewsi''), the magnificent frigatebird (''Fregata magnificens'') and the Ascension frigatebird (''Fregata aquila''). The genus is the only member of the family
Fregatidae Frigatebirds are a Family (biology), family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, l ...
.


Subspecies

Three subspecies are recognised: *''F. a. ariel'' occurs in the central and eastern Indian Ocean, the seas off South East Asian and from northern Australia to the west and central Pacific Ocean. *''F. a. iredalei'' named by the Australian ornithologist Gregory Mathews in 1914. It occurs in the western Indian Ocean and breeds on the
Aldabra Aldabra, the world's second-largest coral atoll (the largest is Kiritimati), is located east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands (Seychelles), Outer Islands ...
atoll. *''F. a. trinitatis'' was named by the Brazilian zoologist
Alípio de Miranda-Ribeiro Alípio de Miranda-Ribeiro (21 February 1874, Rio Preto, Minas Gerais – 8 January 1939) was a Brazilian herpetologist and ichthyologist. His son, Paulo de Miranda-Ribeiro (1901–1965), was also a zoologist. From an early age Alípio de Miran ...
in 1919. It occurs in the South Atlantic off the coast of Brazil and breeds on the Trindade Archipelago. It has disappeared as a breeding bird from the main island, but very small numbers (less than 40 breeding pairs) remain on a small offshore islet. Some ornithologists have questioned the validity of these subspecies as they appeared to differ only in their size. Few museum specimens of the isolated Atlantic ''F. a. trinitatis'' exists, making comparisons difficult, but a comprehensive study published in 2017 found that it differed in both color of plumage and skeletal details, leading to the recommendation of treating it as a separate species (''Fregata trinitatis'').


Description

The lesser frigatebird is the smallest species of
frigatebird Frigatebirds are a Family (biology), family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, l ...
and measures in length with a wingspan of and long forked tails. Male birds weight . Female birds are heavier and weight . Like all frigatebirds the male has a large red sac on the front of the throat which is inflated during courtship. Courtship display also involves a variety of calls, bill rattling and spreading of the wings. The male is mostly all black save for a white patch on the flank which extends on to the underwing as a spur. Males also have a pale bar on the upper wing. Females have a black head and neck with a white collar and breast as well as a spur extending on to the underwing. The female also has a narrow red ring around the eye. Juveniles and immature birds are more difficult to differentiate but the presence of the spurs of white in the armpits is a helpful distinguishing sign. Frigate birds are built for flying; they rarely swim and cannot walk but can manage to climb around the trees and bushes in which they nest. They have a very light skeleton and long narrow wings and are masters of the air. Their name probably derives from the fact that they harass other sea birds such as boobies and tropicbirds as they return to their nests from feeding, forcing them to disgorge their catch, which is then swooped upon and caught by the frigate birds before it reaches the water below. This practice seems to be more common among female frigate birds, but probably only accounts for a fairly small proportion of the diet, which mainly consists of
squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...
and
flying fish The Exocoetidae are a family (biology), family of Saltwater fish, marine Actinopterygii, ray-finned fish in the order (biology), order Beloniformes, known colloquially as flying fish or flying cod. About 64 species are grouped in seven genus, ge ...
scooped up from the surface of the sea.


Distribution

The lesser frigatebird is said to be the most common and widespread frigatebird in Australian seas (Lindsey, 1986). It is common in tropical seas, breeding on remote islands, including Christmas Island in the Indian Ocean in recent years. These birds are most likely to be seen from the mainland prior to the onset of a tropical cyclone, and once this abates they disappear again.


Breeding

Breeding seems to occur between May and December in the Australian region. They nest in trees (on
Christmas Island Christmas Island, officially the Territory of Christmas Island, is an States and territories of Australia#External territories, Australian external territory in the Indian Ocean comprising the island of the same name. It is about south o ...
) and both sexes contribute to nest building and incubation and feeding of the young. One egg is laid which takes 6–7 weeks to hatch. Fledglings are not left alone for another seven weeks or so for fear that they may be attacked and eaten by other birds including other frigate birds. They remain in the nest for another 6 months or so until fledged but they are cared for and fed by their parents for quite a long time after that.


Status

The total world population is estimated to be several hundred thousand birds. At least 6,000 pairs breed on the Aldabra Islands in the Indian Ocean and another 15,000 pairs breed on islands off the north coast of Australia. The largest colonies are on the
Phoenix Islands The Phoenix Islands, or Rawaki, are a group of eight atolls and two submerged coral reefs that lie east of the Gilbert Islands and west of the Line Islands in the central Pacific Ocean, north of Samoa. They are part of the Kiribati, Republic ...
and
Line Islands The Line Islands, Teraina Islands or Equatorial Islands () are a chain of 11 atolls (with partly or fully enclosed lagoons, except Vostok and Jarvis) and coral islands (with a surrounding reef) in the central Pacific Ocean, south of the Hawa ...
in the central Pacific Ocean. Nests placed on the ground are very vulnerable to predation by introduced species such as feral cats. The elimination of cats from Howland, Baker and
Jarvis Island Jarvis Island (; formerly known as Bunker Island or Bunker's Shoal) is an uninhabited coral island located in the South Pacific Ocean, about halfway between Hawaii and the Cook Islands. It is an Territories of the United States#Unincorporated u ...
s has led to the reestablishment and growth of colonies. Baker Island had no nesting lesser frigatebirds in 1965 but after the elimination of the feral cats on the island in around 1970 the birds returned and in 2002 16,200 individuals were recorded. Because of the large overall population and extended range the species is classified by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
as being of
Least Concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...
. In the South Atlantic, lesser frigatebirds (subspecies ''F. a. trinitatis'') once bred on Fernando de Noronha,
Saint Helena Saint Helena (, ) is one of the three constituent parts of Saint Helena, Ascension and Tristan da Cunha, a remote British overseas territory. Saint Helena is a volcanic and tropical island, located in the South Atlantic Ocean, some 1,874 km ...
and Trindade. The Fernando de Noronha and Saint Helena populations disappeared in ancient times and are only known from
subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
remains, estimated to be a few hundred years old. More recently, it disappeared as a breeding bird from the main island of Trindade, effectly restricting its known breeding range to a small rocky islet off the main island. It is unclear whether it breeds on the Martim Vaz Islands, another part of the Trindade archipelago. The main island of Trindade was once covered in forest but after this was destroyed, overgrazing by the introduced goats prevented any recovery. A series of eradication programs in the second half of the 20th century eliminated all the introduced vertebrates other than house mice. Feral cats that had seriously depleted ground nesting birds were finally eradicated in 1998. The islands are part of a Brazilian military area and the human population consists only of a few
Brazilian Navy The Brazilian Navy () is the navy, naval service branch of the Brazilian Armed Forces, responsible for conducting naval warfare, naval operations. The navy was involved in War of Independence of Brazil#Naval action, Brazil's war of independence ...
personnel, limiting easy access for ornithologists. In 1975–1976 the ornithologist
Storrs Olson Storrs Lovejoy Olson (April 3, 1944 – January 20, 2021) was an American biologist and ornithologist who spent his career at the Smithsonian Institution, retiring in 2008. One of the world's foremost avian paleontologists, he was best known ...
visited the island and reported seeing a small colony of 15 nests on a rocky islet just off the southern coast. Ornithologists reported sightings in 1987 in the same general area as the 1975–1976 sightings, followed by a few sightings off the northeastern coast during a 1994–2000 seabird survey, and sightings of a minimum of six individuals in 2014 at the rocky islet of the 1975–1976 sightings. Combined, these sightings suggest that the remaining South Atlantic population is tiny, possibly numbering less than 20 breeding pairs. If recognized as a separate species, as proposed in 2017, this South Atlantic endemic qualifies as
Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
. In Brazil it is considered Critically Endangered.


Gallery

Fregata ariel - Labuan Tawoa - Batuputih (4).JPG Fregata ariel - Labuan Tawoa - Batuputih (3).JPG Fregata ariel - Labuan Tawoa - Batuputih (2).JPG Fregata ariel - Labuan Tawoa - Batuputih (1).JPG


References

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Further reading

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External links


BirdLife International species factsheet

Photos, video and audio recordings on the Internet Bird Collection
{{Taxonbar, from=Q870775 lesser frigatebird Birds of Brazil Birds of the Atlantic Ocean Birds of the Indian Ocean Birds of the Pacific Ocean lesser frigatebird lesser frigatebird Articles containing video clips