Frigatebird
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Frigatebirds are a 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, long, deeply forked tails and long hooked bills. Females have white underbellies and males have a distinctive red gular pouch, which they inflate during the breeding season to attract females. Their wings are long and pointed and can span up to Template:Convert, the largest wing area to body mass ratio of any bird.
Able to soar for weeks on wind currents, frigatebirds spend most of the day in flight hunting for food, and roost on trees or cliffs at night. Their main prey are fish and squid, caught when chased to the water surface by large predators such as tuna. Frigatebirds are referred to as kleptoparasites as they occasionally rob other seabirds for food, and are known to snatch seabird chicks from the nest. Seasonally monogamous, frigatebirds nest colonially. A rough nest is constructed in low trees or on the ground on remote islands. A single egg is laid each breeding season. The duration of parental care is among the longest of any bird species; frigatebirds are only able to breed every other year.
The Fregatidae are a sister group to Suloidea which consists of cormorants, darters, gannets, and boobies. Three of the five extant species of frigatebirds are widespread (the magnificent, great and lesser frigatebirds), while two are endangered (the Christmas Island and Ascension Island frigatebirds) and restrict their breeding habitat to one small island each. The oldest fossils date to the early Eocene, around 50 million years ago. Classified in the genus Limnofregata, the three species had shorter, less-hooked bills and longer legs, and lived in a freshwater environment.
TaxonomyEdit
EtymologyEdit
The term Frigate Bird itself was used in 1738 by the English naturalist and illustrator Eleazar Albin in his A Natural History of the Birds. The book included an illustration of the male bird showing the red gular pouch.<ref>Template:Cite book</ref> Like the genus name, the English term is derived from the French mariners' name for the bird la frégate—a frigate or fast warship.<ref>Template:Cite book</ref> The etymology was mentioned by French naturalist Jean-Baptiste Du Tertre when describing the bird in 1667.<ref name=tertre>Template:Cite book</ref>Template:Efn Alternative names and spellings include "frigate bird", "frigate-bird", "frigate", "frigate-petrel".<ref name="SOED">Template:Cite book</ref>
Christopher Columbus encountered frigatebirds when passing the Cape Verde Islands on his first voyage across the Atlantic in 1492. In his journal entry for 29 September he used the word rabiforçado, modern Spanish rabihorcado or forktail.<ref>Template:Cite journal</ref><ref name=dunn>Template:Cite book</ref>Template:Efn In the Caribbean frigatebirds were called Man-of-War birds by English mariners. This name was used by the English explorer William Dampier in his book An Account of a New Voyage Around the World published in 1697:<ref name=dampier>Template:Cite book</ref>
The Man-of-War (as it is called by the English) is about the bigness of a Kite, and in shape like it, but black; and the neck is red. It lives on Fish yet never lights on the water, but soars aloft like a Kite, and when it sees its prey, it flys down head foremost to the Waters edge, very swiftly takes its prey out of the Sea with his Bill, and immediately mounts again as swiftly; never touching the Water with his Bill. His Wings are very long; his feet are like other Land-fowl, and he builds on Trees, where he finds any; but where they are wanting on the ground.<ref name=dampier/>
ClassificationEdit
Frigatebirds were grouped with cormorants, and sulids (gannets and boobies) as well as pelicans in the genus Pelecanus by Linnaeus in 1758 in the tenth edition of his Systema Naturae. He described the distinguishing characteristics as a straight bill hooked at the tip, linear nostrils, a bare face, and fully webbed feet.<ref name="linnaeus">Template:Cite book</ref> The genus Fregata was introduced by French naturalist Bernard Germain de Lacépède in 1799.<ref>Template:Cite book Page numbering starts at one for each of the three sections.</ref> The type species was designated as the Ascension frigatebird by French zoologist François Marie Daudin in 1802.<ref>Template:Cite book Although the date of 1799 is printed on the title page, this volume was not published until 1802. For a discussion of the date see: Template:Cite journal</ref><ref>Template:Cite book</ref> Louis Pierre Vieillot described the genus name Tachypetes in 1816 for the great frigatebird. The genus name Atagen had been coined by German naturalist Paul Möhring in 1752, though this has no validity as it predates the official beginning of Linnaean taxonomy.<ref name="AFD2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In 1874, English zoologist Alfred Henry Garrod published a study where he had examined various groups of birds and recorded which muscles of a selected group of fiveTemplate:Efn they possessed or lacked. Noting that the muscle patterns were different among the steganopodes (classical Pelecaniformes), he resolved that there were divergent lineages in the group that should be in separate families, including frigatebirds in their own family Fregatidae.<ref name="garrod 1874">Template:Cite journal</ref> Urless N. Lanham observed in 1947 that frigatebirds bore some skeletal characteristics more in common with Procellariiformes than Pelecaniformes, though concluded they still belonged in the latter group (as suborder Fregatae), albeit as an early offshoot.<ref>Template:Cite journal</ref> Martyn Kennedy and colleagues derived a cladogram based on behavioural characteristics of the traditional Pelecaniformes, calculating the frigatebirds to be more divergent than pelicans from a core group of gannets, darters and cormorants, and tropicbirds the most distant lineage.<ref>Template:Cite journal</ref> The classification of this group as the traditional Pelecaniformes, united by feet that are totipalmate (with all four toes linked by webbing) and the presence of a gular pouch, persisted until the early 1990s.<ref name="Hedges94">Template:Cite journal</ref> The DNA–DNA hybridization studies of Charles Sibley and Jon Edward Ahlquist placed the frigatebirds in a lineage with penguins, loons, petrels and albatrosses.<ref>Template:Cite book</ref> Subsequent genetic studies place the frigatebirds as a sister group to the group Suloidea, which comprises the gannets and boobies, cormorants and darters.<ref name = "Hackett2008">Template:Cite journal</ref><ref name=smith/> Microscopic analysis of eggshell structure by Konstantin Mikhailov in 1995 found that the eggshells of frigatebirds resembled those of other Pelecaniformes in having a covering of thick microglobular material over the crystalline shells.<ref>Template:Cite journal</ref>
Molecular studies have consistently shown that pelicans, the namesake family of the Pelecaniformes, are actually more closely related to herons, ibises and spoonbills, the hamerkop and the shoebill than to the remaining species. In recognition of this, the order comprising the frigatebirds and Suloidea was renamed Suliformes in 2010.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In 1994, the family name Fregatidae, cited as described in 1867 by French naturalists Côme-Damien Degland and Zéphirin Gerbe, was conserved under Article 40(b) of the International Code of Zoological Nomenclature in preference to the 1840 description Tachypetidae by Johann Friedrich von Brandt. This was because the genus names Atagen and Tachypetes had been synonymised with Fregata before 1961, resulting in the aligning of family and genus names.<ref>Template:Cite book</ref>
Fossil recordEdit
The Eocene frigatebird genus Limnofregata comprises birds whose fossil remains were recovered from prehistoric freshwater environments, unlike the marine preferences of their modern-day relatives. They had shorter less-hooked bills and longer legs, and longer slit-like nasal openings.<ref name="mayr">Template:Cite book</ref> Three species have been described from fossil deposits in the western United States, two—L. azygosternon and L. hasegawai—from the Green River Formation (48–52 million years old) and one—L. hutchisoni—from the Wasatch Formation (between 53 and 55 million years of age).<ref name="stidham">Template:Cite journal</ref> Fossil material indistinguishable from living species dating to the Pleistocene and Holocene has been recovered from Ascension Island (for F. aquila),<ref>Template:Cite journal</ref> Saint Helena Island,<ref>Template:Cite journal</ref> both in the southern Atlantic Ocean, and also from various islands in the Pacific Ocean (for F. minor and F. ariel).<ref>Template:Cite journal</ref><ref>Template:Cite book</ref> A tarsometatarsus and pedal phalanx from the Lower Eocene London Clay of the Walton-on-the-Naze resembles Limnofregata, but being notably larger and distinct in other ways, was tentatively referred to Marinavis longirostris due to similar stratigraphy, geography, size, and presumed frigatebird affinities.<ref>Template:Cite journal</ref>
A cladistic study of the skeletal and bone morphology of the classical Pelecaniformes and relatives found that the frigatebirds formed a clade with Limnofregata. Birds of the two genera have 15 cervical vertebrae, unlike almost all other Ciconiiformes, Suliformes and Pelecaniformes, which have 17. The age of Limnofregata indicates that these lineages had separated by the Eocene.<ref name=smith>Template:Cite journal</ref>
Living species and infrageneric classificationEdit
Template:Cladogram The type species of the genus is the Ascension frigatebird (Fregata aquila).<ref name="AFD">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> For many years, the consensus was to recognise only two species of frigatebird, with larger birds as F. aquila and smaller as F. ariel. In 1914 the Australian ornithologist Gregory Mathews delineated five species, which remain valid.<ref name=kennedy04>Template:Cite journal</ref><ref>Template:Cite journal</ref> Analysis of ribosomal and mitochondrial DNA indicated that the five species had diverged from a common ancestor only recently—as little as 1.5 million years ago. There are two species pairs, the great and Christmas Island frigatebirds, and the magnificent and Ascension frigatebirds, while the fifth species, the lesser frigatebird, is an early offshoot of the common ancestor of the other four species.<ref name=kennedy04/> Two subspecies of the magnificent, three subspecies of the lesser and five subspecies of the great frigatebird are recognised.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
| Living species of frigatebirds | |||
| Common and binomial names | Image | Description | Range |
|---|---|---|---|
| Magnificent frigatebird (Fregata magnificens) Mathews, 1914 |
File:Fregata magnificens -Galapagos, Ecuador -male-8 (1).jpg | With a body length of Template:Convert, it is the largest species and has the longest bill. The adult male is all-black with a scarlet throat pouch that is inflated like a balloon in the breeding season. Although the feathers are black, the scapular feathers have a purple sheen, in contrast to the male great frigatebird's green sheen. The female is brownish-black, but has a white breast and lower neck sides, a brown band on the wings, and a blueish-grey eye-ring.<ref name=hbwmagnificens>Template:Cite bookTemplate:Subscription required</ref> | Widespread in the tropical Atlantic, it breeds in colonies in trees in Florida, the Caribbean and Cape Verde Islands, as well as along the Pacific coast of the Americas from Mexico to Ecuador, including the Galápagos Islands.<ref name=iucnmagn/> |
| Ascension frigatebird (Fregata aquila) (Linnaeus, 1758) |
File:Male Frigatebird with chick Fregata aquila.jpg | Apart from its smaller size, the adult male is very similar to the magnificent frigatebird. The female is brownish black with a rusty brown mantle and chest, and normally lacks any white patches present on the front of female birds of other species. The occasional female observed with a white belly may be breeding before obtaining the full adult plumage.<ref name=hbwaquila>Template:Cite bookTemplate:Subscription required</ref> | Found on Boatswain Bird Island just off Ascension Island in the tropical Atlantic Ocean, having not bred on the main island since the 1800s.<ref name=iucnascension>Template:Cite iucn</ref> |
| Christmas frigatebird (Fregata andrewsi) Mathews, 1914 |
File:Christmas Island Frigatebird.JPG | The adult male is one of the frigatebird species with white on its belly—an egg shaped patch. It is larger with a longer bill than the related great frigatebird. Its upperparts are black with green metallic gloss on the mantle and scapulars. The female has dark upperparts with brown wing bars, a black head with white belly and white collar (sometimes incomplete) around its neck.<ref name=james>Template:Cite journal</ref> | Breeds only on Christmas Island in the eastern Indian Ocean.<ref name=iucnxmas>Template:Cite iucn</ref> |
| Great frigatebird (Fregata minor) (Gmelin, 1789) |
File:Male greater frigate bird displaying crop.jpg | The adult male has black upperparts with green metallic gloss on the mantle and scapulars. It is completely black underneath with subtle brown barring on the axillaries. The upperparts of the female are dark with lighter brown wing bars. Its head is black with a mottled throat and belly. The neck has a white collar.<ref name=james/> | Found in tropical Indian and Pacific oceans, as well as one colony—Trindade and Martim Vaz—in the south Atlantic, generally where the water is warmer than Template:Convert, and breeding on islands and atolls with sufficient vegetation to nest in.<ref name=iucngrt/> |
| Lesser frigatebird (Fregata ariel) (G. R.Gray, 1845) |
File:Lesser frigatebird lei.jpg | With a body length of around Template:Convert, it is the smallest species. The adult male has black upperparts with greenish to purple metallic gloss on the mantle and scapulars, and is black underneath except for bold white axillary spurs. The upperparts of the female are dark with lighter wing bars. The head is black while the belly and the neck collar are white.<ref name=james/> | Tropical and subtropical waters across the Indian and Pacific Oceans. Atlantic race trinitatis was limited to Trindade, off Eastern Brazil but may now be extinct.<ref name=hbwariel>Template:Cite bookTemplate:Subscription required</ref><ref name=alves>Template:Cite book</ref> |
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DescriptionEdit
Frigatebirds are large slender mostly black-plumaged seabirds, with the five species similar in appearance to each other. The largest species is the magnificent frigatebird, which reaches Template:Convert in length, with three of the remaining four almost as large. The lesser frigatebird is substantially smaller, at around Template:Convert long. Frigatebirds exhibit marked sexual dimorphism; females are larger and up to 25 percent heavier than males,<ref name=hbwFregatidae/> and generally have white markings on their underparts.<ref name=BoB>Template:Cite book</ref> Frigatebirds have short necks and long, slender hooked bills.<ref name=hbwFregatidae/> Their long narrow wings (male wingspan can reach Template:Convert) taper to points. Their wings have eleven primary flight feathers, with the tenth the longest and eleventh a vestigial feather only, and 23 secondaries. Their tails are deeply forked, though this is not apparent unless the tail is fanned.<ref name=obrien/> The tail and wings give them a distinctive 'W' silhouette in flight.<ref name=hbwFregatidae/> The legs and face are fully feathered. The totipalmate feet are short and weak, the webbing is reduced and part of each toe is free.<ref name=obrien/>
The bones of frigatebirds are markedly pneumatic, making them very light and contributing only 5% to total body weight. The pectoral girdle is strong as its bones are fused. The pectoral muscles are well-developed, and weigh as much as the frigatebird's feathers—around half the body weight is made up equally of these muscles and feathers.<ref name=hbwFregatidae/> The males have inflatable red-coloured throat pouches called gular pouches, which they inflate to attract females during the mating season.<ref name=BoB/> The gular sac is, perhaps, the most striking frigatebird feature. These can only deflate slowly, so males that are disturbed will fly off with pouches distended for some time.<ref name=hbwFregatidae/>
Frigatebirds remain in the air and do not settle on the ocean. They produce very little oil from their uropygial glands so their feathers would become sodden if they settled on the surface. In addition, with their long wings relative to body size, they would have great difficulty taking off again.<ref name=hbwFregatidae/>
Distribution and habitatEdit
Frigatebirds are found over tropical oceans, and ride warm updrafts under cumulus clouds. Their range coincides with availability of food such as flying fish, and with the trade winds, which provide the windy conditions that facilitate their flying.<ref name=hbwFregatidae/> They occur as rare vagrants to temperate regions and are not found in polar latitudes. Adults are generally sedentary, remaining near the islands where they breed.<ref name=hbwFregatidae/> However, male frigatebirds have been recorded dispersing great distances after departing a breeding colony—one male great frigatebird relocated from Europa Island in the Mozambique Channel to the Maldives Template:Convert away, and a male magnificent frigatebird flew Template:Convert from French Guiana to Trinidad.<ref name="Weimerskirch 2006">Template:Cite journal</ref> In 2015, a magnificent frigatebird was spotted as far north as Michigan.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Great frigatebirds marked with wing tags on Tern Island in the French Frigate Shoals were found to regularly travel the Template:Convert to Johnston Atoll, although one was reported in Quezon City in the Philippines. Genetic testing seems to indicate that the species has fidelity to their site of hatching despite their high mobility.<ref name=Dearborn>Template:Cite journal</ref> Young birds may disperse far and wide, with distances of up to Template:Convert recorded.<ref name=hbwFregatidae/>
Behaviour and ecologyEdit
Having the largest wing-area-to-body-weight ratio of any bird, frigatebirds are essentially aerial.<ref name=hbwFregatidae/> This allows them to soar continuously and only rarely flap their wings. One great frigatebird, being tracked by satellite in the Indian Ocean, stayed aloft for two months. They can fly higher than 4,000 meters in freezing conditions.<ref>Template:Cite journal</ref> Like swifts they are able to spend the night on the wing, but they will also return to an island to roost on trees or cliffs.<ref name=weimerskirch03>Template:Cite journal</ref> Field observations in the Mozambique Channel found that great frigatebirds could remain on the wing for up to 12 days while foraging.<ref>Template:Cite journal</ref> Highly adept, they use their forked tails for steering during flight and make strong deep wing-beats,<ref name=obrien/> though not suited to flying by sustained flapping. Frigatebirds bathe and clean themselves in flight by flying low and splashing at the water surface before preening and scratching afterwards.<ref name=hbwFregatidae/> Conversely, frigatebirds do not swim and with their short legs cannot walk well or take off from the sea easily.<ref name=obrien/>
According to a study in the journal Nature Communications, scientists attached an accelerometer and an electroencephalogram testing device on nine great frigatebirds to measure if they slept during flight. The study found the birds do sleep, but usually only using one hemisphere of the brain at a time and usually sleep while ascending at higher altitudes. The amount of time mid-air sleeping was less than an hour and always at night.<ref>Template:Cite news</ref>
The average life span is unknown but in common with seabirds such as the wandering albatross and Leach's storm petrel, frigatebirds are long-lived. In 2002, 35 ringed great frigatebirds were recovered on Tern Island in the Hawaiian Islands. Of these ten were older than 37 years and one was at least 44 years of age.<ref name=juola>Template:Cite journal</ref>
Despite having dark plumage in a tropical climate, frigatebirds have found ways not to overheat—particularly as they are exposed to full sunlight when on the nest. They ruffle feathers to lift them away from the skin and improve air circulation, and can extend and upturn their wings to expose the hot undersurface to the air and lose heat by evaporation and convection. Frigatebirds also place their heads in the shade of their wings, and males frequently flutter their gular pouches.<ref name=hbwFregatidae/>
Unlike most seabirds, frigatebirds are thermal soarers, using thermals to glide.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> This is in contrast to birds like albatrosses, which are dynamic soarers, using winds produced by the waves to stay aloft.
Breeding behaviourEdit
Frigatebirds typically breed on remote oceanic islands, generally in colonies of up to 5000 birds. Within these colonies, they most often nest in groups of 10 to 30 (or rarely 100) individuals.<ref name=obrien/> Breeding can occur at any time of year, often prompted by commencement of the dry season or plentiful food.<ref name=hbwFregatidae/>
Frigatebirds have the most elaborate mating displays of all seabirds. The male birds take up residence in the colony in groups of up to thirty individuals.<ref name=hbwFregatidae/> They display to females flying overhead by pointing their bills upwards, inflating their red throat pouches and vibrating their outstretched wings, showing the lighter wing undersurfaces in the process. They produce a drumming sound by vibrating their bills together and sometimes give a whistling call.<ref name=obrien/> The female descends to join a male she has chosen and allows him to take her bill in his. The pair also engages in mutual "head-snaking".<ref name=hbwFregatidae/>
After copulation it is generally the male who gathers sticks and the female that constructs the loosely woven nest. The nest is subsequently covered with (and cemented by) guano. Frigatebirds prefer to nest in trees or bushes, though when these are not available they will nest on the ground. A single white egg that weighs up to 6–7% of mother's body mass is laid, and is incubated in turns by both birds for 41 to 55 days. The altricial chicks are naked on hatching and develop a white down. They are continuously guarded by the parents for the first 4–6 weeks and are fed on the nest for 5–6 months.<ref name=obrien/> Both parents take turns feeding for the first three months, after which the male's attendance trails off leaving the mother to feed the young for another six to nine months on average.<ref name=hbwFregatidae/> The chicks feed by reaching their heads in their parents' throat and eating the part-regurgitated food. It takes so long to rear a chick that frigatebirds generally breed every other year.<ref name=obrien/>
The duration of parental care in frigatebirds is among the longest for birds, rivalled only by the southern ground hornbill and some large accipitrids.<ref>Template:Cite book</ref> Frigatebirds take many years to reach sexual maturity. A study of great frigatebirds in the Galapagos Islands found that they only bred once they have acquired the full adult plumage. This was attained by female birds when they were eight to nine years of age and by male birds when they were ten to eleven years of age.<ref name=valle>Template:Cite journal</ref>
FeedingEdit
Frigatebirds' feeding habits are pelagic, and they may forage up to 500 km (310 mi) from land. They do not land on the water but snatch prey from the ocean surface using their long, hooked bills.<ref name=obrien>Template:Cite book</ref> They mainly catch small fish such as flying fish, particularly the genera Exocoetus and Cypselurus, that are driven to the surface by predators such as tuna and dolphinfish,<ref name=weimerskirch03/> but they will also eat cephalopods, particularly squid.<ref name=obrien/> Menhaden of the genus Brevoortia can be an important prey item where common, and jellyfish and larger plankton are also eaten. Frigatebirds have learned to follow fishing vessels and take fish from holding areas.<ref name=hbwFregatidae/> Conversely tuna fishermen fish in areas where they catch sight of frigatebirds due to their association with large marine predators.<ref name="Weimerskirch 2010">Template:Cite journal</ref> Frigatebirds also at times prey directly on eggs and young of other seabirds, including boobies, petrels, shearwaters and terns, in particular the sooty tern.<ref name=hbwFregatidae/>
Frigatebirds will rob other seabirds such as boobies, particularly the red-footed booby, tropicbirds, shearwaters, petrels, terns, gulls and even ospreys of their catch, using their speed and manoeuvrability to outrun and harass their victims until they regurgitate their stomach contents. They may either assail their targets after they have caught their food or circle high over seabird colonies waiting for parent birds to return laden with food.<ref name=hbwFregatidae/> Although frigatebirds are renowned for their kleptoparasitic feeding behaviour, kleptoparasitism is not thought to play a significant part of the diet of any species, and is instead a supplement to food obtained by hunting.<ref name = "Burger">Template:Cite book</ref> A study of great frigatebirds stealing from masked boobies estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%.<ref>Template:Cite journal</ref>
Unlike most other seabirds, frigatebirds drink freshwater when they come across it, by swooping down and gulping with their bills.<ref name=hbwFregatidae/>
ParasitesEdit
Frigatebirds are unusual among seabirds in that they often carry blood parasites. Blood-borne protozoa of the genus Haemoproteus have been recovered from four of the five species.<ref>Template:Cite journal</ref> Bird lice of the ischnoceran genus Pectinopygus and amblyceran genus Colpocephalum and species Fregatiella aurifasciata have been recovered from magnificent and great frigatebirds of the Galapagos Islands. Frigatebirds tended to have more parasitic lice than did boobies analysed in the same study.<ref>Template:Cite journal</ref>
A heavy chick mortality at a large and important colony of the magnificent frigatebird, located on Île du Grand Connétable off French Guiana, was recorded in summer 2005. Chicks showed nodular skin lesions, feather loss and corneal changes, with around half the year's progeny perishing across the colony. An alphaherpesvirus was isolated and provisionally named Fregata magnificens herpesvirus, though it was unclear whether it caused the outbreak or affected birds already suffering malnutrition.<ref name="de Thoisy">Template:Cite journal</ref>
Status and conservationEdit
Populations and threatsEdit
Two of the five species are considered at risk.<ref name=hbwFregatidae/> In 2003, a survey of the four colonies of the critically endangered Christmas Island frigatebirds counted 1200 breeding pairs. As frigatebirds normally breed every other year, the total adult population was estimated to lie between 1800 and 3600 pairs. Larger numbers formerly bred on the island, but the clearance of breeding habitat during World War II and dust pollution from phosphate mining have contributed to the decrease.<ref name=iucnxmas/><ref name=james14>Template:Cite journal</ref> The population of the vulnerable Ascension frigatebird has been estimated at around 12,500 individuals.<ref name=ratcliffe08>Template:Cite journal</ref> The birds formerly bred on Ascension Island itself, but the colonies were exterminated by feral cats introduced in 1815. The birds continued to breed on a rocky outcrop just off the shore of the island. A program conducted between 2002 and 2004 eradicated the feral cats<ref>Template:Cite journal</ref> and a few birds have returned to nest on the island.<ref>Template:Cite news</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The other three species are classified by the International Union for Conservation of Nature as being of Least Concern. The populations of all three are large, with that of the magnificent frigatebird thought to be increasing,<ref name=iucnmagn>Template:Cite iucn</ref> while the great and lesser frigatebird decreasing.<ref name=iucngrt>Template:Cite iucn</ref><ref name=iucnlssr>Template:Cite iucn</ref> Monitoring populations of all species is difficult due to their movements across the open ocean and low reproductivity. The status of the Atlantic populations of the great and lesser frigatebirds are unknown and possibly extinct.<ref name=hbwFregatidae/>
As frigatebirds rely on large marine predators such as tuna for their prey, overfishing threatens to significantly impact on food availability and jeopardise whole populations.<ref name="Weimerskirch 2010"/> As frigatebirds nest in large dense colonies in small areas, they are vulnerable to local disasters that could wipe out the rare species or significantly impact the widespread ones.<ref name=hbwFregatidae/>
HuntingEdit
In Nauru, catching frigatebirds was an important tradition still practised to some degree. Donald W. Buden writes: "Birds typically are captured by slinging the weighted end of a coil of line in front of an approaching bird attracted to previously captured birds used as decoys. In a successful toss, the line becomes entangled about the bird's wing and bringing [sic] it to ground."<ref>Template:Cite journal</ref> Marine birds including frigatebirds were once harvested for food on Christmas Island but this practice ceased in the late 1970s.<ref name=james14/> Eggs and young of magnificent frigatebirds were taken and eaten in the Caribbean.<ref name=hbwFregatidae/> Great frigatebirds were eaten in the Hawaiian Islands and their feathers used for decoration.<ref>Template:Cite book</ref>
Cultural significanceEdit
The frigate bird appears on the national Flag of Kiribati. The design is based on its former colonial Gilbert and Ellice Islands coat of arms. The bird also appears on the flag of Barbuda, and is the national bird of Antigua and Barbuda.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
There are anecdotal reports of tame frigatebirds being kept across Polynesia and Micronesia in the Pacific. A bird that had come from one island and had been taken elsewhere could be reliably trusted to return to its original home, hence would be used as a speedy way to relay a message there.<ref name=hbwFregatidae/> There is evidence of this practice taking place in the Gilbert Islands and Tuvalu.<ref name="Lewis1994">Template:Cite book</ref>
The great frigatebird was venerated by the Rapa Nui people on Easter Island; carvings of the birdman Tangata manu depict him with the characteristic hooked beak and throat pouch.<ref>Template:Cite book</ref> Its incorporation into local ceremonies suggests that the now-vanished species was extant there between the 1800s and 1860s.<ref>Template:Cite book</ref>
Maritime folklore around the time of European contact with the Americas held that frigatebirds were birds of good omen as their presence meant land was near.<ref name=hbwFregatidae/>
See alsoEdit
Explanatory notesEdit
ReferencesEdit
External linksEdit
- Frigatebird videos, photos and sounds on the Internet Bird Collection
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