Great frigatebirds are also sometimes known as "man o'-war birds," a reference to their aggressiveness towards other birds and an analogy to the fast "frigate" or "man o'war" ships used by pirates. Great frigatebirds are also known as "iwa" in Hawai'ian, a name which means "thief."
Great frigatebirds are generally quiet, but they make a variety of sounds in different contexts, especially at breeding colonies. They snap their bills and squawk at birds that are too close to them in breeding colonies. Hatchlings use a harsh begging call, along with bobbing of their heads and spread wings. Adults call to young as they return also, to let them know they are coming with food. Males call more than females but there are no songs. There are 3 kinds of calls: landing calls, warbling, and reeling calls. Landing calls occur when adults are returning to the breeding colony, although females are usually quiet. Warbling and reeling calls are used by males during courtship displays, along with bill-rattling. These calls may be used when flying over potential female mates or when engaging in mutual head-waving as part of courtship. Great frigatebirds also use bill-snapping or rattling and vibrations of their mandibles to make sounds. Bill-snapping is used in agressive interactions, rattling and vibrations are used in courtship.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Great frigatebirds are considered "least concern" by the IUCN because of their large population sizes and range. Populations have historically declined, primarily because of disturbance at historical breeding colonies and destruction of nesting habitats. In addition, introduced predators can seriously impact nesting populations. Populations may still be declining, but there is little data to understand the pattern of decline. They are protected by the U.S. Migratory Bird Treaty Act. Great frigatebird adults and young are captured and eaten by humans and die when they collide with man-made structures.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
There are no adverse effects of great frigatebirds on humans. They live on remote, offshore islands and over open ocean. They may take fish scraps from commercial fishing operations or steal small fish from nets or baited hooks.
Great frigatebirds are important members of pelagic ocean ecosystems. Adults, nestlings, and eggs are collected for food in some areas. On islands in the Pacific young frigatebirds were sometimes raised as pets and used to convey messages from traveling islanders to their homes. Nesting colonies contribute to guano deposits.
Positive Impacts: food ; produces fertilizer
Great frigatebirds commonly forage and nest with other species of seabirds. They will steal food from other seabirds as well, especially from boobies, tropicbirds, and petrels. Parasites reported include feather lice (Phthiraptera), including the species Colopocephalum angulaticeps, Fregatiella aurifasciata, and Pectinopygus gracilicornis, and hippoboscid flies (Olfersia spinifera).
Species Used as Host:
Commensal/Parasitic Species:
Great frigatebirds are best known for their kleptoparasitic habits; they frequently steal food from other sea birds by harassing them until they drop their prey or regurgitate a recent meal. They pursue other birds, especially near nesting colonies, diving at them and grabbing them until they release their food. Great frigatebirds then dive rapidly to catch the released prey or regurgitate before it hits the water. Bird species commonly harassed by great frigatebirds are boobies (Sula), tropicbirds (Phaethon), and petrels (Pterodroma). However, great frigatebirds capture most of their food themselves, by grabbing fish at or just below the water's surface.
Great frigatebirds eat mainly flying fish (Exocoetidae) and squid (Ommastrephidae) found within 15 cm of the ocean surface. Most foraging occurs over deep, ocean waters in areas where upwelling, divergence, or convergence brings nutrient rich water close to the surface. They may also feed over schools of large, predatory fish (Katsuwonus and Euthynnus species ) or dolphins (Stenella, Delphinus, and Steno species) that drive smaller fish to the surface. Great frigatebirds will also feed opportunistically in coastal areas on turtle hatchlings, fish scraps from commercial fishing operations, and on seabird nestlings in breeding colonies, including great frigatebird nestlings from their own nesting colonies. They are often seen foraging in large, mixed-species flocks, especially flocking with sooty terns (Sterna fuscata) and wedge-tailed shearwaters (Puffinus pacificus). Great frigatebirds occasionally drink fresh water by dipping their bill into water while in flight.
Animal Foods: birds; reptiles; fish; mollusks
Primary Diet: carnivore (Piscivore , Molluscivore )
Great frigatebirds are found in tropical waters globally. They occur between 25 degrees north and 25 degrees south. Nesting colonies are known from offshore islands throughout the tropical Pacific, western Atlantic, and south Indian oceans. Most of what is known about great frigatebirds is known from nesting colonies and there is little information about their range and movements outside of the breeding season. Males and females may occupy separate ranges outside of the breeding season. Great frigatebirds are considered sedentary, although individuals disperse from nesting areas to broader ranges when not breeding.
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )
Great frigatebirds are found over open, tropical ocean waters and near offshore, oceanic nesting islands. Males and females may occupy different ranges outside of the breeding season, which may be influenced by their different wing loading characteristics and the nature of winds over different areas of the ocean. When not breeding, great frigatebirds wander widely to feed on fish and squid in areas with high concentrations of prey, such as at ocean upwellings, divergences, and convergences. Great frigatebirds breed on islands without predators. They nest in trees and shrubs, such as beach naupaka (Scaevola sericea), beach heliotrope (Tournefortia argentea), pisonia (Pisonia grandis), and mangroves (Bruguiera and Rhizophora species). Nests are usually above 0.5 m and may be several kilometers inland on larger islands. Great frigatebirds are superb soaring birds and do not need to come to land frequently to roost. They can soar for long period of time, including overnight.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: pelagic
There is little available information on longevity in great frigatebirds. The oldest banded bird lived to 37 years and a maximum age of 40 years is estimated and from 25 to 30 years is considered a typical lifespan. At one site, during a productive year, between 60 and 70% of eggs laid were successfully raised to fledging. But complete failure, or failure rates of up to 81% are reported from El Niño years when food is scarce.
Range lifespan
Status: wild: 37 (high) years.
Typical lifespan
Status: wild: 40 (high) years.
Great frigatebirds have highly specialized for life in flight. They have the highest ratio of wing are to body mass of any bird. They have exceptionally long wings for soaring, long, forked tails for maneuverability in flight, and very small legs and feet. Their legs and feet are so small that they cannot walk on them, only perching between flights. Great frigatebirds are also one of few seabird species that are sexually dimorphic in both size and plumage. Males are smaller than females and are entirely black, with a greenish-purple sheen dorsally. Females are larger, with a black head and black feathers dorsally, but with a white chin and chest that merges into their white belly. Males have a large, red, inflatable gular sac that becomes enlarged during the breeding season and is used in courtship displays. Male gular sacs become smaller and fades in color outside of the breeding season. Immature individuals are similar to females in plumage, but with light rufous feathers on the head and between the grey chin and chest and white belly. Great frigatebirds are distinctive birds, most often seen soaring above the water, where their long, forked tail and long, pointed wings held in a "W" shape make them easy to identify. They have long bills with a strongly hooked tip. They are from 85 to 105 cm in body length, from 205 to 230 cm in wingspan, and from 1 to 1.8 kg mass.
Great frigatebirds are likely to be confused only with other frigatebirds, especially in their immature or juvenile plumages. Incomplete understanding of regional variation in plumage patterns, vocalizations, and soft body parts in widespread species, such as great, lesser, and magnificent frigatebirds may also complicate identifications.
There are 5 recognized subspecies of great frigatebirds. Subspecies vary in body size, plumage, eye ring color, and bill color, but patterns of variation have not been well described. Subspecies are defined geographically and banding studies suggest that there may be little migration of individuals among regions. Subspecies are: F. m. minor in the eastern Indian Ocean and Australia, F. m. aldabra in the western Indian Ocean, F. m. palmerstoni throughout western and central Pacific, F. m. ridgwayi in the eastern Pacific, and F. m. nicolli in the western Atlantic.
Great frigatebirds seem to maintain body temperatures of about 40 degrees Celsius, shivering at lower temperatures. Nestlings are dependent on parents to protect them from the heat of the tropical sun. They use a variety of body postures to help radiate or absorb heat.
Range mass: 1 to 1.8 kg.
Range length: 85 to 105 cm.
Range wingspan: 205 to 230 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently; male more colorful; ornamentation
There are no reported natural predators of adults, although humans will capture adults, eggs, and young to eat. Eggs and nestlings may be preyed on by other frigatebirds (Fregata), owls (Strigiformes), and introduced predators such as rats (Rattus) and domestic cats (Felis catus). Bristle-thighed curlews (Numenius tahitiensis) have been reported eating their eggs.
Known Predators:
Great frigatebirds form monogamous, mated pairs yearly. If a pair is unsuccessful in mating, then they may divorce and select a new mate to attempt breeding. Extra-pair copulations are frequent and males often attempt to copulate with mated females when their mates are absent.
Males display in tight groups on a shrub or tree, often only 1 to 1.5 meters apart. They display continuously for several days until they acquire a mate. Females soar above display sites to assess males. Courtship displays involve a male inflating his bright red gular sac, pointing his head and bill upwards, vibrating the wings while they are extended, and using a warble vocalization and bill-rattling. Males orient themselves towards females that are soaring above. Courtship display then proceeds to reeling vocalization and rolling the head from side to side. Once a female chooses a male, they spend several days close to each other and occasionally engaging in mutual head waving.
Mating System: monogamous
Great frigatebird females breed only every 2 years or less often. Males occasionally breed yearly, but typically breed only as often as every 2 years. The timing of breeding varies substantially with region and the breeding season is extended. Breeding is seasonal in a region, but breeding is recorded from December through September throughout their range. Eggs are typically laid in a 5 to 6 month period, but eggs have been observed throughout the year. Seasonality of breeding in a region is probably linked to regional food availability. In nest clusters within a colony, egg-laying and hatching may be fairly synchronous. Once a pair bond has formed, a nest has been prepared, and an egg is laid, mates do not interact much, even when they exchange caretaking responsibilities. Time from courtship to nest building may be as little as a few days or as long as 4 weeks. Nests are generally platforms built of twigs, sticks, and other collected materials on the same trees or bushes that were used by males for courtship displays, resulting in clustered nesting colonies of 3 to 50 nests and 0.6 to 1.4 m between nests. Nests are generally sheltered from the wind but in full sun. Occasional nests are built on the ground. Generally a single, white egg is laid, but rare nests with 2 eggs or nestlings have been observed. It is possible that the eggs were laid by more than one female. Females may lay a second egg in a season if the first fails or is destroyed. Eggs are incubated immediately after laying and are never left unattended. Young begin to fly at 150 days old. They remain on the nest for 150 to 428 days after fledging, where they continue to be fed and protected by their parents. Fledglings remain near the nest for 10 to 16 months after hatching, at which point they disperse to the ocean. Great frigatebirds have an extended period of adolescence and attain sexual maturity between 5 and 7 years old. Occasionally individuals with immature plumage have been observed breeding.
Breeding interval: Great frigatebirds breed as often as every 2 years, but generally mate less often.
Breeding season: Breeding is seasonal in a region, but breeding is recorded from December through September throughout their range.
Range eggs per season: 1 to 1.
Range fledging age: 150 (low) days.
Range time to independence: 300 to 578 days.
Range age at sexual or reproductive maturity (female): 5 to 7 years.
Range age at sexual or reproductive maturity (male): 5 to 7 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Once a mated pair is formed, one or the other of the parents stays at the nest site until the nestling is 4 to 6 weeks old. Both parents incubate the egg and brood the nestling. Parents take turns incubating the egg from 3 to 18 days at a time. Typical incubation shift lengths are from 4.1 to 6.4 days long, but they vary regionally and are probably related to the distance the other parent has to travel to be able to forage. Females incubate for longer than males, in general. Young are altricial at hatching, naked and with their eyes closed. They grow very slowly, possibly as an adaptation to low or variable food availability. Growth rates vary with the availability of food. They are fed 2 to 4 times a day in their first few weeks and only every 1 to 2 days later in their deelopment. Nestlings are not left unattended by a parent until they are about 1 month old. By 14 days old nestlings are covered in white down and they develop flight plumage and begin flying by 150 days after hatching. They remain in the nest for 150 to 428 days after fledging and continue to be cared for by their parents during that time.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
TheGreat Frigatebird(Fregata minor) is a largedispersiveseabirdin thefrigatebirdfamily. Major nesting populations are found in thePacific(includingGalapagos Islands) andIndian Oceans, as well as a population in theSouth Atlantic.
The Great Frigatebird is a lightly built large seabird up to 105cm long with predominantly black plumage. The species exhibitssexual dimorphism; the female is larger than the adult male and has a white throat and breast, and the male's scapular feathers have a purple-green sheen. In breeding season, the male is able to distend its striking red gular sac. The species feeds on fish taken in flight from the ocean's surface (mostlyflyingfish), and indulges inkleptoparasitismless frequently than other frigatebirds. They feed inpelagicwaters within 80km (50mi) of theirbreeding colonyor roosting areas.
The great frigatebird (Fregata minor) is a large seabird in the frigatebird family. There are major nesting populations in the tropical Pacific Ocean, such as Hawaii and the Galápagos Islands; in the Indian Ocean, colonies can be found in the Seychelles (on Aldabra and Aride Islands) and Mauritius, and there is a tiny population in the South Atlantic, mostly on and around St. Helena and Boatswain Bird Island (Ascension Island).
The great frigatebird is a large and lightly built seabird up to 105 cm long with predominantly black plumage. The species exhibits sexual dimorphism; the female is larger than the adult male and has a white throat and breast, and the male's scapular feathers have a purple-green sheen. In the breeding season, the male is able to distend his striking red gular sac. The species feeds on fish taken in flight from the ocean's surface (mostly flying fish), and indulges in kleptoparasitism less frequently than other frigatebirds. They feed in pelagic waters within 80 km (50 mi) of their breeding colony or roosting areas.
The great frigatebird was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it in the genus Pelecanus and coined the binomial name Pelecanus minor.[2] Gmelin based his description on the "lesser frigate pelican" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds.[3][4] Latham, in turn, largely based his account on the "man of war bird" that had been described and illustrated by the English naturalist George Edwards in 1760.[5] The great frigatebird is now one of five closely-related species of frigatebird that make up their own genus (Fregata) and family (Fregatidae). Its closest relative, within the group, is the Christmas Island frigatebird (Fregata andrewsi).[6][7] Due to the rules of taxonomy, the species name of minor has been retained. This has led to the discrepancy of minor (Latin for "smaller") in contrast with its common name.[8]
A Late Pleistocene fossilised wing phalanx and proximal end of humerus (indistinguishable from the extant great frigatebird) were recovered from Ulupau Head on Oahu.[9]
Five subspecies are usually recognised:[7]
The great frigatebird measures 85 to 105 cm (33 to 41 in) in length and has a wingspan of 205–230 cm (81–91 in).[10] Male great frigatebirds are smaller than females, but the extent of the variation varies geographically.[11] The male birds weigh 1,000–1,450 g (2.20–3.20 lb) while the heavier female birds weigh 1,215–1,590 g (2.679–3.505 lb).[12]
Frigatebirds have long narrow pointed wings and a long narrow deeply forked tail. They have the highest ratio of wing area to body mass and the lowest wing loading of any bird. This has been hypothesized to enable the birds to use marine thermals created by small differences between tropical air and water temperatures. The plumage of males is black with scapular feathers that have a green iridescence when they refract sunlight. Females are black with a white throat and breast and have a red eye ring. Juveniles are black with a rust-tinged white face, head, and throat.
The great frigatebird has a wide distribution throughout the world's tropical seas. Hawaii is the northernmost extent of their range in the Pacific Ocean, with around 10,000 pairs nesting mostly in the Northwestern Hawaiian Islands. In the Central and South Pacific, colonies are found on most island groups from Wake Island to the Galápagos to New Caledonia with a few pairs nesting on Australian possessions in the Coral Sea. Colonies are also found on numerous Indian Ocean islands, the most well-known include the Seychelles islands of Aldabra and Aride, Christmas Island, the Maldives and Mauritius. The Atlantic population is very small, restricted to Ascension Island, St. Helena, and the Brazilian islands of Trindade and Martin Vaz.
Great frigatebirds undertake regular migrations across their range, both regular trips and more infrequent widespread dispersals. Birds marked with wing tags on Tern Island in the French Frigate Shoals were found to regularly travel to Johnston Atoll (873 km), one was reported in Quezon City in the Philippines.[13] One male great frigatebird relocated from Europa Island in the Mozambique Channel to the Maldives 4400 km away for four months, where it fed on rich fishing grounds.[14] Despite their extended range, birds also exhibit philopatry, breeding in their natal colony even if they travel to other colonies.[15]
The great frigatebird forages in pelagic waters within 80 km (50 mi) of the breeding colony or roosting areas. Flying fish from the family Exocoetidae are the most common item in the diet of the great frigatebird; other fish species and squid may be eaten as well. Prey is snatched while in flight, either from just below the surface or from the air in the case of flying fish flushed from the water. Great frigatebirds will make use of schools of predatory tuna or pods of dolphins that push schooling fish to the surface.[16] Like all frigatebirds they will not alight on the water surface and are usually incapable of taking off should they accidentally do so. They are often seen foraging in large, mixed-species flocks, especially flocking with sooty terns and wedge-tailed shearwaters.[17]
Great frigatebirds will also hunt seabird chicks at their breeding colonies, taking mostly the chicks of sooty terns, spectacled terns, brown noddies, black noddies and even from other great frigatebirds.[18] Studies show that only females (adults and juveniles) hunt in this fashion, and only a few individuals account for most of the kills.[19] Great frigatebirds will also feed opportunistically in coastal areas on turtle hatchlings and fish scraps from commercial fishing operations.[20]
Great frigatebirds will attempt kleptoparasitism, chasing other nesting seabirds (boobies, tropicbirds and gadfly petrels[21] in particular) in order to make them regurgitate their food. This behaviour is not thought to play a significant part of the diet of the species, and is instead a supplement to food obtained by hunting. 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%.[22]
Great frigatebirds are seasonally monogamous, with a breeding season that can take two years from mating to the end of parental care. The species is colonial, nesting in bushes and trees (and on the ground in the absence of vegetation) in colonies of up to several thousand pairs. Nesting bushes are often shared with other species, especially red-footed boobies and other species of frigatebirds.
Both sexes have a patch of skin at the throat that is the gular sac; in male great frigatebirds this skin is red and can be inflated to attract a mate. Groups of males sit in bushes and trees and force air into their sac, causing it to inflate over a period of 20 minutes into a startling red balloon. As females fly overhead the males waggle their heads from side to side, shake their wings and call. Females will observe many groups of males before forming a pair bond. Having formed a bond the pair will sometimes select the display site, or may seek another site, to form a nesting site; once a nesting site has been established both sexes will defend their territory (the area surrounding the nest that can be reached from the nest) from other frigatebirds.
Pair bond formation and nest-building can be completed in a couple of days by some pairs and can take a couple of weeks (up to four) for other pairs. Males collect loose nesting material (twigs, vines, flotsam) from around the colony and off the ocean surface and return to the nesting site where the female builds the nest. Nesting material may be stolen from other seabird species (in the case of black noddies the entire nest may be stolen) either snatched off the nesting site or stolen from other birds themselves foraging for nesting material. Great frigatebird nests are large platforms of loosely woven twigs that quickly become encrusted with guano. There is little attempt to maintain the nests during the breeding season and nests may disintegrate before the end of the season.
A single dull chalky-white egg measuring 68 mm × 48 mm (2.7 in × 1.9 in) is laid during each breeding season.[23] If the egg is lost the pair bond breaks; females may acquire a new mate and lay again in that year. Both parents incubate the egg in shifts that last between 3–6 days; the length of shift varies by location, although female shifts are longer than those of males. Incubation can be energetically demanding, birds have been recorded losing between 20 and 33% of their body mass during a shift.
Incubation lasts for around 55 days. Great frigatebird chicks begin calling a few days before hatching and rub their egg tooth against the shell. The altricial chicks are naked and helpless, and lie prone for several days after hatching. Chicks are brooded for two weeks after hatching after which they are covered in white down, and guarded by a parent for another fortnight after that. Chicks are given numerous meals a day after hatching, once older they are fed every one to two days. Feeding is by regurgitation, the chick sticks its head inside the adults mouth.
Parental care is prolonged in great frigatebirds. Fledging occurs after four to six months, the timing dependent on oceanic conditions and food availability.[10] After fledging chicks continue to receive parental care for between 150 and 428 days; frigatebirds have the longest period of post-fledging parental care of any bird. The length of this care depends on oceanic conditions, in bad years (particularly El Niño years) the period of care is longer. The diet of these juvenile birds is provided in part by food they obtained for themselves and in part from their parents. Young fledglings will also engage in play; with one bird picking up a stick and being chased by one or more other fledglings. After the chick drops the stick the chaser attempts to catch the stick before it hits the water, after which the game starts again. This play is thought to be important in developing the aerial skills needed to fish.
Great frigatebirds take many years to reach sexual maturity and only breed once they have acquired the full adult plumage. This is attained by female birds when they are eight to nine years of age and for male birds when they are 10 to 11 years of age.[24] The average lifespan is unknown but is assumed to be relatively long. As part of a study conducted in 2002 on Tern Island in Hawaii, 35 ringed great frigatebirds were recaptured. Of these 10 were 37 years or older and one was at least 44 years old.[25]
Because of the large overall total population and extended range the species is classified by the International Union for Conservation of Nature as being of Least Concern.[1]
In the South Atlantic, great frigatebirds (subspecies F. m. nicolli) once bred on both Saint Helena and Trindade. The Saint Helena population disappeared in ancient times and is only known from subfossil remains, estimated to be a few hundred years old.[26] The Trindade archipelago is part of a Brazilian military area and the human population consists only of a few Brazilian Navy personnel, limiting easy access for ornithologists. Once abundant, it has disappeared as a breeding bird from the main island of Trindade,[27] but small numbers remain elsewhere in this archipelago.[26][28][29] The main island 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.[27] In Brazil, the only country where F. m. nicolli survives, the great frigatebird is considered critically endangered.[29]
Male in flight, Galápagos Islands
Juvenile male in flight
Female in flight
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Another female in flight
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Male, Galápagos Islands
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Female, Galápagos Islands
The great frigatebird (Fregata minor) is a large seabird in the frigatebird family. There are major nesting populations in the tropical Pacific Ocean, such as Hawaii and the Galápagos Islands; in the Indian Ocean, colonies can be found in the Seychelles (on Aldabra and Aride Islands) and Mauritius, and there is a tiny population in the South Atlantic, mostly on and around St. Helena and Boatswain Bird Island (Ascension Island).
The great frigatebird is a large and lightly built seabird up to 105 cm long with predominantly black plumage. The species exhibits sexual dimorphism; the female is larger than the adult male and has a white throat and breast, and the male's scapular feathers have a purple-green sheen. In the breeding season, the male is able to distend his striking red gular sac. The species feeds on fish taken in flight from the ocean's surface (mostly flying fish), and indulges in kleptoparasitism less frequently than other frigatebirds. They feed in pelagic waters within 80 km (50 mi) of their breeding colony or roosting areas.
