Frigate Birds: Characteristics, Behaviour, Flying and Courting

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male magnificent frigatebird

Frigate birds are large birds with a wings span of up to 2.3 meters (7.5 feet) but they are best known for the enormous red pouches that males have under their bills which they inflate during their courting ritual. Unlike most other ocean going birds frigate birds can't dive which partly explains why they often harass other birds — usually boobies — and make them drop their catch which the frigatebirds scoop up in mid flight. Frigates are fast, maneuverable boats. The birds' name is an allusion to their speed and maneuverability.

Frigatebirds belong to seabird family Fregatidae (frigatids) which comprises a single genus (Fregata) with five species. They can be found in pelagic (open ocean) and coastal environments in tropical and subtropical oceans around the globe. Breeding grounds are located on remote oceanic islands or in coastal mainland mangrove regions.[Source: Laura Howard, Tanya Dewey, Animal Diversity Web (ADW) /=]

Frigatebirds may live for at least 25-37 years. A frigatebird fossil (Limnofregata) from Wyoming has been dated to the Eocene Period (56 million to 33.9 million years ago) but the evolutionary relationships of frigatids remain unclear. Frigatebirds have been considered related to other totipalmate birds (tropicbirds, anhingas, gannets and boobies, pelicans, cormorants and anhingas), which the form Pelecaniformes group.

Frigatebirds tend to live on remote, offshore islands and and spend time over the open ocean and don't come into contact with humans so much. They occasionally take fish scraps from commercial fishing operations or steal small fish from nets or baited hooks. In the past on some Pacific islands, young frigatebirds were sometimes raised as pets and used to convey messages from traveling islanders to their homes.

Two frigatebird species are included in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species: Andrew's Frigatebird (Fregata andrewsi) is listed as 'Critically Endangered' and Ascension Frigatebird (F. aquila) is listed as 'Vulnerable'. Major threats include: habitat degradation, introduced predators, and human disturbance at breeding sites. Frigatebird eggs and young are collected for human consumption. There are no reported natural predators of adult frigatebirds although humans in some places capture adults and takes eggs, and young to eat. Eggs and nestlings are much more vulnerable. They are preyed upon by other frigatebirds, owls, and introduced predators such as rats and domestic cats.

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Encyclopedia of Life; Smithsonian Oceans Portal ; MarineBio

Great Frigatebirds

Great frigatebirds (Scientific name: Fregata minor) are also sometimes known as "man o'-war birds," a reference to their aggressiveness towards. Man-of-wars were 18th-century armed sailing ship, sometimes used by pirates. Great frigatebirds are also known Hawai'ian as "iwa" — meaning "thief." The oldest banded great frigatebirds. lived to 37 years and it is estimated that the maximum age of the birds is 40 years old, with 25 to 30 years considered a typical lifespan. Their population rates go through booms and busts. At one site, during a productive year, between 60 and 70 percent of eggs laid were successfully raised to fledging. But during El Niño years when food is scarce failure rates of up to 81 percent have been reported. from [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

range of great frigatebird

Great frigatebirds are found in tropical waters around the world between 25̊ north and 25̊ south. Nesting colonies exist on offshore islands throughout the western Atlantic, tropical Pacific and Indian oceans. Most of what is known about great frigatebirds is what has been observed at nesting colonies and little is known about their range and movements outside of the breeding season.

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 are listed under "least concern" on International Union for Conservation of Nature (IUCN) Red List because of their large population sizes and range. They are protected under the U.S. Migratory Bird Act They have no special status according to the Convention on the International Trade in Endangered Species (CITES). 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.

Magnificent Frigatebirds

Magnificent frigatebirds (Scientific name: Fregata magnificens) live along the coastlines of tropical North and South America.. They breed as far north as 25̊ north latitude in Mexico and Florida and as far south 27̊ south latitude in Brazil. They are especially common in southern Florida, the Gulf Coast, the Caribbean islands and the west coast of Mexico. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

Adult magnificent frigatebirds range in weight from 1.7 to 1.8 kilograms (3.7 to 4 pounds) and range in length from one to 2.3 meters (three feet 7.5 feet). Their wingspan ranges from 0.9 to 2.3 meters (2.95 to 7.5 feet). Females are 15 percent larger than males. Sexes are colored or patterned differently with the male being more colorful. Ornamentation is different. There is little data on magnificent frigatebird lifespan, but it is estimated to be at least 30 years.

range of magnificent frigatebird

Magnificent frigatebirds are most often seen soaring along coastlines. Their silhouette is easily recognized. They are also recognizable by their large size and long, hooked bill and have short legs and small feet like other frigatebirds that are unsuited for walking or swimming. According to Animal Diversity Web> Male magnificent frigatebirds are entirely black except for brown inner secondaries on the upper wing and the presence of a red inflatable throat pouch called a gular sac. They also have faint purple gloss on the head and green on the neck, scapulars, and upper wing. Their legs and feet appear back or grayish. Females are also entirely black with a white chest and white and tan markings on the wings. Their legs and feet are flesh-colored or pink, and they lack a gular sac. Immature magnificent frigatebirds have a white head and chest while the rest of the body is black. Their legs, feet, and bill are light-bluish gray. Their large heads, long, pointed, narrow wings, and forked tails make them easy to distinguish even from a distance. /=\

Frigatebird Characteristics

Frigatebirds are large birds. Adults range in length from 89 to 114 centimeters (2.9 to 3.7 feet) in length, weigh 0.6 to 1.7 kilograms and have a wingspan of 1.9 to 2.5 meters (6.2 to 8.2 feet). Females tend to be larger and heavier than males. The legs and feet of females are white or red while those of males are mostly black or brown, Both sexes have brood patches. [Source: Laura Howard, Animal Diversity Web (ADW)]

Frigatebirds are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them), warm-blooded (homoiothermic, having a constant body temperature, usually higher than the temperature of their surroundings) and have bilateral symmetry (both sides of the animal are the same). Great frigatebirds seem to maintain body temperatures of about 40̊ Celsius (104̊F) , 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.

According to Animal Diversity Web:Plumage is mostly iridescent black-brown and some species have white on the breast and/or abdomen. The gular sac is red and becomes greatly enlarged when inflated by males performing mating displays. Wings are long, narrow and pointed, and the tail is long and deeply forked. Head is small and neck is relatively short. The long, cylindrical bill is strongly hooked at the tip and palate is desmognathous. Small feet are totipalmate with a small area of webbing at base of toes. Coracoid and furcula are fused to the sternum (unique in birds).

Great Frigatebird Physical Characteristics

Male frigate bird
Great frigatebirds range in weight from one to 1.8 kilograms (2.20 to 3.96 pounds) and range in length from 85 to 105 centimeters (33.46 to 41.34 inches). Their wingspan ranges from two to 2.3 meters (80.71 to 90.55 inches). Great frigatebirds are also one of few seabird species that are sexually dimorphic in both size and plumage. Females are larger than males. Sexes are colored or patterned differently with the male being more colorful. Males are entirely black, with a greenish-purple sheen dorsally. Females have a black head and black feathers dorsally, but with a white chin and chest that merges into their white belly. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Male great frigatebirds 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.

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 five 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: 1) F.M. minor in the eastern Indian Ocean and Australia, 2) F.M. aldabra in the western Indian Ocean, 3) F.M. palmerstoni throughout western 4) central Pacific, F.M. ridgwayi in the eastern Pacific, and 5) F.M. nicolli in the western Atlantic./=\

Frigatebird Flying and Life in the Air

Magnificent frigatebirds are birds of the open sea. They nest in coastal areas but are in flight the majority of their adult lives. Often they are seen over open water far from land. Their wings are large and ideal for soaring and taking advantage of upward air currents. They can glide for long distances without beating their wings and shift their their long, forked tails to turn and maneuver around. Magnificent frigatebirds are one of the few birds that can fly in hurricane-force winds. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

Great frigatebirds are also exceptional soaring birds that can stay aloft for long periods of time. They do not need to come to land frequently to roost. Highly specialized for flight and life in the air, they can even soar overnight and have the highest ratio of wing to body mass of any bird. They have exceptionally long wings which helps them soar and long, forked tails, which aid their 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. [Source: Tanya Dewey /=]

Great frigatebirds rarely land on the ground or on the water, except maybe to pick up nesting material or by accident. Their short legs and small feet make them ungainly on the ground and make it difficult to propel themselves out of the water. Their feet are not webbed. However, they can soar for many hours without flapping, taking advantage of updrafts over water. Great frigatebirds rarely soar over nesting colonies rather than roost, when the winds are right. They are more likely to roost in calm winds and fly around in storms and high winds,. Great frigatebirds have exceptionally low wing loading, which differs between sexes because of their differences in size. This may explain why sexes are segregated geographically outside of the breeding season. /=\

Frigatebird Behavior and Communication

magnificent frigatebirds in the air in Belize

Frigatebirds generally spend most of the the year within range of their breeding colony. Young birds may disperse widely. Frigatebirds are noted soarers, as described above, spending much of the day riding the winds and roosting at night on trees or cliffs. Thermoregulation includes gular fluttering, feather ruffling, and wing extending. [Source: Laura Howard, Animal Diversity Web (ADW)]

Great frigatebirds are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), move around within a well-defined range, territorial (defend an area within the home range), and social (associates with others of its species; forms social groups. Great frigatebirds are sometimes considered sedentary because they remain in the same area, although individuals disperse from nesting areas to broader ranges when not breeding. There is no firm data on home range, but estimates suggest that great frigatebirds feed from 80 to 500 kilometers from their colony. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Great frigatebirds often roost at night, although they often soar throughout the night as well. While roosting and in nesting colonies they defend small display and nesting sites with bill-snapping, vocalizations, lunging, and gular displays among males. These territories are very small, so that individuals are able to touch each other. Great frigatebirds forage in flocks, sometimes with multiple seabird species, and roost in groups of just a few to thousands. Nesting colonies are large and often include other species, such as red-footed boobies black noddies and white terns.

Magnificent frigatebirds are usually solitary in flight but nest in colonies with numerous other pairs of the same species and sometimes with seabirds of ther species. According to Animal Diversity Web:. While feeding, they can be extremely aggressive towards other animals. They are otherwise docile and while on land will often allow humans to come very close and even touch them. While their legs are not well-suited to walking, their strong, webbed toes allow them to perch when not in flight. Aggression, while rare, is usually in the form of bill snapping and jabbing at other birds when competing for perch sights. They do not defend territory beyond their small nest areas. Fledglings' often interact in playful ways. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

Frigatebirds communicate with vision and sound and sense using vision, touch, sound and chemicals usually detected with smell. 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 three 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.

Frigatebird Feeding and Food Thievery

Frigatebirds feed primarily on flying fish and also feed menhaden (kind of small fish) squid or jellyfish. They also prey upon eggs and chicks of their own species, boobies, terns and petrels and shearwaters. Frigatebirds catch most of their prey by flying low over the water and picking prey from near the surface. When opportunities present themselves they will take fish from fishing boats or offal from slaughterhouses. [Source: Laura Howard, Animal Diversity Web (ADW)]

Frigatebirds are famous for cooperatively stealing prey from other species. Several frigatebirds soar together and target other seabirds such as boobies, who are adept at diving and catch prey in the sea and carrying food items in the air. When stealing prey frigatebirds swoop down from above to pursue their target birds, pulling at the birds' wings or tail, in an attempt to force the birds to disgorge and drop their prey items. If successful, the dropped food items are plucked from the air by one of the agile frigatebirds or maybe scooped up from the ocean surface. /=\

sea bird colony with frigatebirds, terns and gannets
Magnificent frigatebirds eat mainly fish and squid as well as jellyfish and crustaceans. Their diet can vary greatly depending on food availability and preferred hunting technique. The three main hunting techniques are dipping, kleptoparasitism, and opportunistic feeding. When dipping, these birds gracefully glide just above the surface of the water and skim the surface with their beak to catch fish. However, they are only able to dip about 15 centimeters deep to avoid getting their feathers wet. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

Great frigatebirds frequently harass other sea birds are force them to 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. Among the bird species most commonly targeted are boobies, tropicbirds and petrels. Despite this, great frigatebirds capture most of their food themselves, by grabbing fish at or just below the water's surface. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Great frigatebirds eat mainly flying fish and squid found within 15 centimeters of the ocean surface. According to Animal Diversity Web: 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 or dolphins 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 and wedge-tailed shearwaters. Great frigatebirds occasionally drink fresh water by dipping their bill into water while in flight. /=\

Frigatebird Reproduction

Frigatebirds are oviparous (young are hatched from eggs) and offspring are produced in successive annual or seasonal cycles. They engage in seasonal breeding. There is some evidence that great frigatebirds return to the same area to breed. For most frigate birds breeding is every two years, although in some populations females breed biennially whereas males may breed annually. Great frigatebirds breed as often as every two years, but generally mate less often. Females generally breed every two years or less. Males occasionally breed yearly, but typically breed every two years.

The beginning of breeding is variable and often coincides with food availability. For great frigatebirds, the breeding season varies from place to place in both the timing of breeding and how long the breeding season lasts but breeding is recorded from December through September throughout most of their range. Females and reach sexual maturity at five to seven years. Males reach sexual maturity at five to seven years. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Frigatebirds are considered seasonally monogamous. 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.

Frigatebird Male Courtship Displays and Mating

Male great frigatebird displaying
Male frigate birds are famous for their courtship displays. In the Galapagos Islands frigate birds put on the their courtship display during the first six months of the year. After a male has found what he thinks is a good nesting site he inflates his gular sacs which expand like brilliant red heart-shape balloon. When he spots a cruising female he flaps his wings, shakes his head and bellows like a rutting elephant.

During the breeding season, male magnificent frigatebirds congregate at male display sites. They inflate their large, red, gular sacs, which can can inflate to such great size they obscure can the bird's head. During courtship displays, males rapidly vibrate their wings and sit back on their tails. They stretch their wings out and throw their heads back for maximum display of the gular sac. Females then inspect the males. As females attempt to find a preferred mate, males twist and bend to make their gular sac look as large a possible, they also make a loud, drumming noise during this display. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

For great frigatebirds, according to Animal Diversity Web: During the breeding season, males gather in groups to display for females by spreading their wings, inflating their large scarlet gular sacs, and pointing their bills skywards. When a female flies over the group, each male quivers wings and head, and the bill vibrates against the inflated pouch producing a distinctive drumming sound. A female will land next to one male and two or three days of pair-formation ensues with periods of head snaking and the male taking the female's bill into his own. The pair takes two to three weeks to build a nest on the display site. The male collects nesting material (sometimes pilfering from nearby nests) whereas the female defends the site and builds a nest from the materials brought by the male. Copulations occur at the nest site. [Source: Laura Howard /=]

Males display in tight groups on a shrub or tree, often only one 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. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Frigatebird Nesting

After a male successfully woes a female the two of them build a nest together and take turns guarding the egg during the eight week incubation period. After the chick is born the parents must maintain a vigil against cannibalistic frigate birds and short eared owls for five months until the young birds can fly. Frigatebirds may breed in mixed colonies with other sea birds such as red-footed boobies, , terns, noddies, gulls, cormorants, , shearwaters and petrels and pelicans.

Frigatebirds breed in colonies numbering up to several thousand pairs. Nest-sites include trees, bushes, and cliffs. Among the materials used for nesting are twigs, leaves, seaweed, grass, and feathers. Females generally lay one whitish egg per clutch.
Both sexes have brood patches and parents take turns incubating for 40-55 days in stints lasting from one to 18 days. Males and females take turns brooding and feeding chicks regurgitated food until chicks fledge at four to seven months. Chicks are guarded constantly during the first month, then left alone frequently while the parents forage. Post-fledging care is prolonged (14-18 months) and the female may do most, if not all, of the post-fledging feeding. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=\

Magnificent frigatebirds usually build their nests out of twigs on or around low-lying vegetation. Males gather twigs and other nest building materials while females remain at the males' display site and build the nest there. Nests are primarily constructed at ground level, but sometimes in trees as well. Great frigatebirds breed on islands without predators. They nest in trees and shrubs, such as beach heliotrope, pisonia, beach naupaka, and mangroves. Nests are usually at least 50 centimeters above sea level and may be several kilometers inland on larger islands. Eggs are typically laid in a five to six month period, but eggs have been observed throughout the year. Seasonality of breeding in a region is probably linked to regional food availability. [Source: Martha Calcutt, Animal Diversity Web (ADW) /=]

Among great frigatebirds, according to Animal Diversity Web: 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 three to 50 nests and 0.6 to 1.4 meters 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 two 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.

Once a mated pair is formed, one or the other of the parents stays at the nest site until the nestling is 4 to six weeks old. Both parents incubate the egg and brood the nestling. Parents take turns incubating the egg from three 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.

Frigatebird Fledglings and Development

Frigatebird eggs are incubated for 40-55 days. Chicks are altricial (born relatively helpless and in need of significant parental care) and acquire a whitish down. Chicks are brooded and fed by parents. Fledging age is variable and ranges from 4.5-7 months. Post-fledging care may last from four to eighteen months depending on species. Adult plumage may be acquired between four or six years. Age of first breeding varies with species and ranges from six to eleven years. [Source: Laura Howard, Animal Diversity Web (ADW)

Greater frigatebird eggs are incubated immediately after laying and are never left unattended. During the pre-fertilization stage provisioning and protecting is done by females. During the pre-birth and pre-weaning stages provisioning is done by females and protecting is done by males and females. During the pre-independence stage provisioning and protecting are done by males and females. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Greater frigatebird young are altricial. 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 two to four times a day in their first few weeks and only every one to two days later in their deelopment. Nestlings are not left unattended by a parent until they are about one 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.

Young remain in 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 five and seven years old. Occasionally individuals with immature plumage have been observed breeding.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023

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