Red-tailed tropical bird
| Red-tailed tropical bird | ||||||||||
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Red-tailed tropical bird ( Phaethon rubricauda ) |
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| Phaethon rubricauda | ||||||||||
| Boddaert , 1783 |
The red-tailed tropical bird ( Phaethon rubricauda ) is a species of bird from the order Phaethontiformes and lives above the subtropical and tropical Indo-Pacific . In contrast to the other two tropical bird species, it is absent over the Atlantic.
The IUCN classifies the red-tailed tropical bird as not endangered ( least concern ).
Appearance
Red-tailed tropical birds reach a body length of 95 to 104 centimeters, while the elongated tail feathers account for about 35 centimeters. The wingspan is 111 to 119 centimeters. The weight averages 800 grams.
They are white, the plumage of freshly molted birds has a pink tinge. The shafts of the hand wings and tail feathers are black. There is a crescent-shaped black spot above the eye. The tail has 16 control feathers, the two middle ones are long and blood red. They are narrower than the other tropical bird species. Despite their apparent conspicuousness, these elongated control springs are often difficult to spot when observing the field. The legs are pale blue, the feet black. The beak is red.
Juvenile animals have a pattern of black horizontal stripes on the top. They still lack the two long tail feathers and the beak is black, turning yellow or orange with age. They show their age dress at the age of two to three years.
The red-tailed tropical bird can be confused with several species of birds that do not belong to the tropical bird family. The herring head gull has shorter wings and a leaner build. Body proportions and flight image are reminiscent of the great tern , but the body structure of the red-tailed tropical bird is overall stronger and red-tailed tropical birds, unlike these, do not have any gray on the upper side of the body.
Typical behaviors
The red-tailed tropical bird typically flies high above the water's surface. Characteristic for his flight pattern are very regular, almost mechanical-looking wing beats, in between he repeatedly inserts glide phases in which he neither gains nor loses altitude. He is one of the shock divers who plunge down to the surface of the water from the flight phase to catch food. The tail rises high when floating on the water. Usually the red-tailed tropical bird can only be observed individually over the sea, in the breeding colonies they are socialized in loose groups. The legs are set very far back on the body and the feet are too weak to support the body weight. They crawl by leaning on their chest and push themselves forward with their wings with the help of their beak until they have found a place from which they can take off again.
Distribution area
The distribution area of the red-tailed tropical bird is the tropical Indian and Pacific oceans. They occur here roughly between 40 ° S and 40 ° N. Occasionally, wanderers are also observed far inland. Outside of the breeding season, red-tailed tropical birds can generally only be observed above the high seas.
Red-tailed tropical birds breed on Mauritius , Madagascar , the Seychelles , on islands off Western Australia and Queensland, New Caledonia , Ogasawara-gunto , the Kermadec and Society Islands and on Hawaii .
Food and subsistence
Red-tailed tropical birds mainly eat fish and cephalopods. They catch their food by thrusting. They plunge vertically into the water from a height of six to 50 meters. The high altitude compensates for the fact that the red-tailed tropical birds are not very streamlined. Occasionally they also catch flying fish during their flight phase. The food is occasionally swallowed underwater, otherwise while the bird is swimming on the water. They almost never fly up if they are still holding prey in their beak.
The large beak in relation to the body size, which they can also open wide, enables this species to catch relatively large fish. Usually red-tailed tropical birds search for food alone, but they are occasionally associated with other tropical birds or sea birds.
Reproduction
Red-tailed tropical birds are monogamous birds. On Christmas Island and the Kure Atoll , the couple relationship continues for several breeding periods. They either breed singly or in loose colonies. The nesting density may depend more on suitable breeding locations and is anywhere from a meter or two or up to 70 meters. Some islands only have one or two nests of red-tailed tropical birds. It has not yet been investigated at what age they form the couple bond. However, there are some indications from observations on the Kure Atoll that the pairs form a year before the first brood. A nest is not built, the only egg from which the clutch consists, as with all tropical birds, is deposited in a shallow hollow. Nesting sites are caves, crevices and ledges on cliffs, occasionally the nesting site is up to forty meters from the edge of the cliff. The egg is matt light brown and oval in shape. If the egg or chick is lost, a new clutch occurs within one to two months.
Both parent birds breed and take care of the young birds. When brooding, they break away on average every eight days on the Kure Atoll, but every six days on Christmas Island. The breeding season is 41 to 48 days. When hatching, the chick is already covered with gray or white down that is one to one and a half centimeters long. You are initially blind, the eyes open on the second or third day of life. During the first week of life, the chicks are hoofed by a parent bird, after which they either sit under one of the parent bird's wings or the parent bird sits next to the nesting trough. In the first week of life, the chicks only open their beak when they are touched. The parent birds trigger an opening of its beak by touching it at the base of the beak. After a week, however, the chicks begin to beg for any birds that are found near the nesting trough. They usually bring in food once or twice a day. With increasing age of the nestling, the parent birds stay less and less in the vicinity of the nestling. Presumably, the presence of the parent birds ends when the young bird has reached the age of six weeks.
Reproduction rate and causes of mortality
The reproduction rate of red-tailed tropical birds is not high: a maximum of 46 to 50 percent of the clutches grows into a young bird by the time they fled; on the Kure Atoll there were only 38 and 17 young birds per 100 eggs that fledged in two reproductive periods . No young birds grow up on Christmas Island during the El Niño-Southern Oscillation . This is presumably due to the fact that the surface temperature of the foraging grounds then rises and there are no fish, which are the food source of the red-tailed tropical birds. Heavy rains, which also occur during this time, also contribute to the lack of breeding success.
The predators of the red-tailed tropical bird include white-bellied sea eagles and ospreys , which beat brooding adults and older nestlings. The herring head gull and ravens eat eggs and chicks. The gathering of eggs or the hunting of birds by humans is considered to be the more significant cause of death. On the Norfolk Island feral domestic cats are a threat to this species, on Christmas Island it is not only domestic cats but also dogs that kill birds of this species. On Aldabra , red-tailed tropical birds are also believed to fall victim to palm thieves . Heat stress is another major cause of death.
supporting documents
literature
- Gerald Tuck, Hermann Heinzel : The sea birds of the world. Parey, Hamburg / Berlin 1980, ISBN 3-490-07818-7 .
- National Geographic Society: Field Guide to the Birds of North America, Second Edition . National Geographic, ISBN 0-87044-692-4
- Martin R. De LA Pena: Birds of Southern South America and Antarctica (Collins Illustrated Checklist) . Harpercollins Pub Ltd, ISBN 0-00-220077-5
- K. Simpson & N. Day: Field Guide to the Birds of Australia a Book of Identification . ISBN 0-7470-3023-5
- PJ Higgins (Eds.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0-19-553068-3
Web links
- Phaethon rubricauda in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on 13 August, 2009.
- Videos, photos and sound recordings of Red-tailed Tropicbird (Phaethon rubricauda) in the Internet Bird Collection