Ariel frigate bird
| Ariel frigate bird | ||||||||||
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Ariel frigate bird ( Fregata ariel ) |
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| Fregata ariel | ||||||||||
| ( Gray , 1845) |
The ariel frigate bird ( Fregata ariel ) is a sea bird from the family of frigate birds (Fregatidae) and the smallest species of the family. Ariel frigate birds are widespread in the tropical waters of the Pacific. They are also found in a small region off the Atlantic coast of Brazil.
The IUCN classifies the ariel frigate bird as not endangered ( least concern ) and estimates the population at 200,000 sexually mature individuals.
features
It reaches a body length of 71 to 81 cm and a wingspan of 175 to 193 cm. Males weigh 625 to 875 g, females weigh 760 to 955 g. The adult male is completely black with a green, bluish, or purple tinge. In females, the upper breast is white.
Ariel frigate birds look for food individually or in loose groups exclusively over tropical waters. They usually fly very high above the surface of the water and are dexterous and agile fliers. In flight, sweeping wing beats alternate with long gliding phases. Often they follow boats and ships. Outside of the breeding season, they are rarely seen on land. They are usually quiet over the sea, whistling, screeching and squeaking sounds can be heard from them in the breeding colonies.
Subspecies and distribution
There are three very similar subspecies, which only differ in their wingspan and beak length.
- Fregata ariel ariel , central and eastern Indian Ocean , western and central Pacific .
- Fregata ariel iredalei , western Indian Ocean.
- Fregata ariel trinaitatis , southern Atlantic , only breeds on Trindade .
Way of life
Ariel frigate birds live over tropical seas (water temperature over 22 ° C) and breed on small islands far away from the mainland. They feed mainly on 10 to 20 cm long flying fish (Exocoetidae) and flying squids (Ommastrephidae). They only dip their beak into the water. Caught fish are turned in the beak while in flight and then swallowed head first. They also eat eggs and chicks from other seabirds and carrion. Especially the females steal the catch of other seabirds such as terns and gannets in particular ( kleptoparasitism ).
Young ariel frigate birds that were ringed in the south-central Pacific , moved with the prevailing winds into the Coral Sea northeast of Australia , then north via New Guinea to the Philippines , some as far as Japan .
Reproduction
Ariel frigate birds enter into a monogamous couple relationship, which, however, presumably only lasts one reproductive period. Successfully breeding ariel frigate birds only raise a young bird every other year. Presumably they breed for the first time when they are four to five years old. Both parent birds breed and are involved in the care of the young bird. During courtship, a parent bird always remains at the nesting site, after egg-laying the parent birds only meet each other when they break away during the brood.
Ariel frigate birds nest in colonies on small islands in bushes and mangroves, also in lower vegetation than the banded frigate bird ( F. minor ); on some islands like Rawaki and the Line Islands also on the ground. Reproduction often falls in the dry season. The breeding colonies are often mixed with other coarse pods . The nest is a platform made of twigs and branches. The nesting material is mainly collected by the male and built by the female. The high point of construction activity falls in the first ten days of courtship, but ariel frigate birds often continue to build the nest until the young bird hatches.
The clutch consists of an egg that is incubated for around 45 days. The chicks are initially naked, later they grow white down . They are fully fledged after 20 to 24 weeks and then cared for by their parents for about four to six months. On Aldabra , 297 eggs only hatched 59 chicks, 36 of which fledged. This meant that the reproductive success on this island was only 12 percent. It is generally assumed that the breeding success is negatively correlated with the nest density. Almost a third of chick deaths were due to an unmated male occupying the nest. On Christmas Island , feral cats are essential predators of ariel frigate birds.
supporting documents
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 84-87334-10-5 .
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683
Web links
- Fregata ariel in the Red List of Threatened Species of the IUCN 2009. Posted by: BirdLife International, 2008. Accessed January 28 of 2010.
- Videos, photos and sound recordings of Fregata ariel in the Internet Bird Collection
- BirdLife Factsheet on the Ariel Frigate Bird