Frigatebird
Encyclopedia
The frigatebirds are a family, Fregatidae, of seabird
s. There are five species
in the single genus
Fregata. They are also sometimes called Man of War birds or Pirate birds. Since they are related to the pelican
s, the term "frigate pelican" is also a name applied to them. They have long wings, tails and bills and the males have a red gular pouch that is inflated during the breeding season to attract a mate.
Frigatebirds are pelagic piscivore
s which obtain most of their food on the wing. A small amount of their diet is obtained by robbing other seabirds
, a behaviour that has given the family its name, and by snatching seabird chicks. Frigatebirds are seasonally monogamous
, and 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 in frigatebirds is the longest of any bird.
Frigatebirds are found over tropical oceans and ride warm updrafts. Therefore, they can often be spotted riding weather fronts and can signal changing weather patterns.
These birds do not swim and cannot walk well, and cannot take off from a flat surface. Having the largest wingspan to body weight ratio of any bird, they are essentially aerial, able to stay aloft for more than a week, landing only to roost or breed on trees or cliffs.
As members of Pelecaniformes
, frigatebirds have the key characteristics of all four toes being connected by the web, a gular sac (also called gular skin
), and a furcula
that is fused to the breastbone. Although there is definitely a web on the frigatebird foot, the webbing is reduced and part of each toe is free. Frigatebirds produce very little oil and therefore do not land in the ocean. The gular sac is used as part of a courtship display and is, perhaps, the most striking frigatebird feature.
They generally lay one white egg per clutch. Both parents take turns feeding for the first three months but then only the mother feeds the young for another eight months. It takes so long to rear a chick that frigatebirds cannot breed every year. It is typical to see juveniles as big as their parents waiting to be fed. When they sit waiting for endless hours in the hot sun, they assume an energy-efficient posture in which their head hangs down, and they sit so still that they seem dead. But when the parent returns, they will wake up, bob their head, and scream until the parent opens its mouth. The hungry juvenile plunges its head down the parent's throat and feeds at last.
Distribution and identifying characteristics differ among frigatebird species, and thus are addressed in species-specific articles.
Frigatebirds' feeding habits are pelagic. Lacking the ability to take off from water, they snatch prey from the ocean surface or beach using their long, hooked bills. They catch fish, baby turtles and similar items in this way. Frigatebirds will rob other seabird
s such as boobies
, tropicbirds, and shearwater
s of their catch, using their speed and manoeuvrability to outrun and harass their victims until they regurgitate their stomach contents. 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. A study of Great Frigatebird
s stealing from Masked Boobies
estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%.
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s. There are five species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the single genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Fregata. They are also sometimes called Man of War birds or Pirate birds. Since they are related to the pelican
Pelican
A pelican, derived from the Greek word πελεκυς pelekys is a large water bird with a large throat pouch, belonging to the bird family Pelecanidae....
s, the term "frigate pelican" is also a name applied to them. They have long wings, tails and bills and the males have a red gular pouch that is inflated during the breeding season to attract a mate.
Frigatebirds are pelagic piscivore
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
s which obtain most of their food on the wing. A small amount of their diet is obtained by robbing other seabirds
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
, a behaviour that has given the family its name, and by snatching seabird chicks. Frigatebirds are seasonally monogamous
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
, and nest colonially. A rough nest is constructed in low trees or on the ground on remote islands. A single egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
is laid each breeding season. The duration of parental care in frigatebirds is the longest of any bird.
Morphology
Frigatebirds are large, with iridescent black feathers (the females have a white underbelly), with long wings (male wingspan can reach 2.3 metres) and deeply-forked tails. The males have inflatable red-coloured throat pouches called "gular pouches", which they inflate to attract females during the mating season.Frigatebirds are found over tropical oceans and ride warm updrafts. Therefore, they can often be spotted riding weather fronts and can signal changing weather patterns.
These birds do not swim and cannot walk well, and cannot take off from a flat surface. Having the largest wingspan to body weight ratio of any bird, they are essentially aerial, able to stay aloft for more than a week, landing only to roost or breed on trees or cliffs.
As members of Pelecaniformes
Pelecaniformes
The Pelecaniformes is a order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes...
, frigatebirds have the key characteristics of all four toes being connected by the web, a gular sac (also called gular skin
Gular skin
Gular skin , in ornithology, is an area of featherless skin on birds that joins the lower mandible of the beak to the bird's neck....
), and a furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....
that is fused to the breastbone. Although there is definitely a web on the frigatebird foot, the webbing is reduced and part of each toe is free. Frigatebirds produce very little oil and therefore do not land in the ocean. The gular sac is used as part of a courtship display and is, perhaps, the most striking frigatebird feature.
Breeding behavior
See also Unusual Seabird Breeding BehaviorUnusual seabird breeding behavior
The term seabird is used for many families of birds in several orders that spend the majority of their lives at sea. Seabirds make up some, if not all, of the families in the following orders: Procellariiformes, Sphenisciformes, Pelecaniformes, and Charadriiformes. Many seabirds remain at sea for...
They generally lay one white egg per clutch. Both parents take turns feeding for the first three months but then only the mother feeds the young for another eight months. It takes so long to rear a chick that frigatebirds cannot breed every year. It is typical to see juveniles as big as their parents waiting to be fed. When they sit waiting for endless hours in the hot sun, they assume an energy-efficient posture in which their head hangs down, and they sit so still that they seem dead. But when the parent returns, they will wake up, bob their head, and scream until the parent opens its mouth. The hungry juvenile plunges its head down the parent's throat and feeds at last.
Distribution and identifying characteristics differ among frigatebird species, and thus are addressed in species-specific articles.
Feeding
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s such as boobies
Booby
A booby is a seabird in the genus Sula, part of the Sulidae family. Boobies are closely related to the gannets , which were formerly included in Sula.-Description:...
, tropicbirds, and shearwater
Shearwater
Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus Calonectris and many smaller species in the genus Puffinus...
s of their catch, using their speed and manoeuvrability to outrun and harass their victims until they regurgitate their stomach contents. Although frigatebirds are renowned for their kleptoparasitic feeding behaviour
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
, 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. A study of Great Frigatebird
Great Frigatebird
The Great Frigatebird is a large dispersive seabird in the frigatebird family. Major nesting populations are found in the Pacific and Indian Oceans, as well as a population in the South Atlantic....
s stealing from Masked Boobies
Masked Booby
The Masked Booby, Sula dactylatra, is a large seabird of the booby family, Sulidae. This species breeds on islands in tropical oceans, except in the eastern Atlantic; in the eastern Pacific it is replaced by the Nazca Booby, Sula granti, which was formerly regarded as a subspecies of Masked Booby...
estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%.
Species
- Genus Fregata
- Magnificent FrigatebirdMagnificent FrigatebirdThe Magnificent Frigatebird was sometimes previously known as Man O'War, reflecting its rakish lines, speed, and aerial piracy of other birds....
or Man O'War, Fregata magnificens. - Ascension FrigatebirdAscension FrigatebirdThe Ascension Frigatebird breeds only on the tiny Boatswain Bird Island just off Ascension Island in the tropical Atlantic Ocean. It formerly bred on the larger island, but was exterminated by introduced cats, Brown Rats, and human persecution.It breeds on the rocky slopes of Boatswainbird...
, Fregata aquila. - Christmas Frigatebird, Fregata andrewsi.
- Great FrigatebirdGreat FrigatebirdThe Great Frigatebird is a large dispersive seabird in the frigatebird family. Major nesting populations are found in the Pacific and Indian Oceans, as well as a population in the South Atlantic....
, Fregata minor. - Lesser FrigatebirdLesser FrigatebirdThe Lesser Frigatebird, Fregata ariel, is a species of frigatebird.It nests in Australia, among other locations.There is a single record from the Western Palearctic, from Eilat in the Gulf of Aqaba....
, Fregata ariel.
- Magnificent Frigatebird
External links
- Frigatebird videos on the Internet Bird Collection