Tropical birds
| Tropical birds | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Red-billed tropical bird ( Phaethon aethereus ) |
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| Systematics | ||||||||||
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| Scientific name of the order | ||||||||||
| Phaethontiformes | ||||||||||
| Sharpe , 1891 | ||||||||||
| Scientific name of the family | ||||||||||
| Phaethontidae | ||||||||||
| Brandt , 1840 | ||||||||||
| Scientific name of the genus | ||||||||||
| Phaethon | ||||||||||
| Linnaeus , 1758 |
The tropical birds ( Phaethon ) are a genus of sea birds of tropical oceans that includes three closely related and very similar species. They are placed in their own family (Phaethontidae) and their own order (Phaethontiformes). The birds are slender and mostly white, their heads and wings are drawn in black. The inner pair of tail feathers is extremely elongated in the adult birds, while the tail of the young is wedge-shaped.
features
Tropical birds are distantly reminiscent of terns , but are larger than them. Their body length is about 50 cm (without the elongated tail feathers), the wingspan about 1 m. The weight is between 300 and 750 g. The completely water-repellent plumage is white, black eye stripes and black wing markings are sharply defined. Sometimes the plumage is tinged with pink or orange.
The two central tail feathers, which are sometimes longer than body length, are striking. They wear out very quickly, so they are often replaced. In two of the three species these feathers are white, in the red-tailed tropical bird they are bright red. They play a role in courtship, perhaps as an aid to maintaining balance in flight.
The legs are short and start far behind the body. Since the feet are also very small, tropical birds move very awkwardly on land. They push their stomach over the ground and can only cover short distances. The beak is large, slender and pointed; it is colored bright red or yellow.
The four webbed toes are the only noticeable feature that tropical birds have in common with the barefoots , in whose taxonomic proximity they were previously placed (see section Systematics ). Unlike these, tropical birds have a feathered throat and clearly visible nostrils.
There is no pronounced gender dimorphism ; at most, the colors of the male are somewhat stronger and brighter.
distribution and habitat
All species are extremely widespread: the red-tailed tropical bird can be found over the Indian and Pacific Oceans , the other two species even over all three oceans. A water temperature between 24 and 30 ° C is preferred, so that tropical birds mostly occur within the tropics . They spend most of their life in the air. They are often found several hundred kilometers from any coast. They only come ashore to breed, and only on remote islands or inaccessible stretches of coast, where there is no danger from land predators. The only species that appear is the red-billed tropical bird , which also breeds on some islands in the Red Sea , occasionally near southern European coasts.
Way of life
nutrition
As shock divers, they hunt fish and cephalopods , using a technique similar to that of the gannet : From a height of 25 m and more, with half-open wings they strike prey, which they prey close below or on the surface of the water. Flying fish and flying squids , which can be captured without touching the water surface, are particularly often hunted.
Reproduction
Tropical birds become sexually mature at the age of 3–4 years. The animals breed on tropical islands where they form small colonies with little social interaction. The breeding grounds can be on inaccessible cliffs, on small islands where there is no danger from ground predators , but also on sandy coastlines, hidden under the vegetation. On Christmas Island, tropical birds even breed in trees in the mountainous interior of the island. The breeding season is regionally very different; it often falls in spring and summer, but on some islands there are breeding individuals all year round.
The brood is preceded by a spectacular courtship flight . To do this, several tropical birds in a colony gather and fly up and down near the breeding sites, calling loudly. When a couple has found each other, they separate from the others. The partners ascend to great heights together in order to slide downwards synchronously up to a few hundred meters. Typically, one partner flies directly above the other and lowers its wings while the lower one raises its wings. So the wing tips almost touch each other. Also, the elongated tail feathers are often bent down so that they touch the partner, or they are waved back and forth. The partners often swap roles during the descent.
Ultimately, the pair ends up at a suitable nesting site and usually copulates immediately after landing. If the ground permits, a small hollow is dug for the egg; a nest is not built. If suitable nesting sites are rare, there can be fights for such sites. The opponents hack each other's head with their beaks. If they are successful, the couple that previously brooded on the spot must give up their egg or young. The constant fighting means that in some places only 30% of the broods are successful. Tropical birds also use this aggressiveness against other species: Sometimes they successfully drive petrels away and take over their nesting sites.
A single egg is laid. The eggs of tropical birds are extremely variable; there are white, gray, brown or red eggs, some monochrome, others spotted or spotted. This is another difference to the other copepods families, which only contain white eggs. The egg is incubated by both partners for 40 to 46 days. The young are initially fed with pre-digested food, which the parent bird chokes into the boy's throat. Over time, it is left alone more often, the intervals between feedings increase, and at 70 to 90 days of age it makes its first flight and does not return to the nesting site.
The maximum age of the tropical birds is unknown, but in any case exceeds twenty years.
Tribal history
Tropical birds are a very old family of birds. The genera Lithoptila and Prophaethon appeared as early as the Paleocene and Eocene , but it was occasionally doubted that these really were true tropical birds; at least it has become customary to separate the genus into a separate family Prophaethontidae.
The oldest doubtless tropical bird comes from the Miocene of Australia and belongs to the extinct genus Heliadornis . This genus was also found in Europe, so it was apparently very widespread.
Systematics
Traditionally, tropical birds were placed in the order of the coarse pods . From the other representatives of the order, however, they differ so strongly that they were often separated in a subordination to Phaethontes. More recently, however, there has been increasing evidence that tropical birds are not closely related to the copepods or to any other bird order. For this reason, they have recently been put into their own order, the Phaethontiformes.
There are three types:
- Red-billed tropical bird ( Phaethon aethereus ), 60–100 cm long, lives in the tropical Atlantic, Eastern Pacific and Indian Oceans. With fewer than 10,000 breeding pairs worldwide, this species is probably the rarest.
- White-tailed tropical bird ( Phaethon lepturus ), 40–80 cm long, widespread in tropical waters other than the Eastern Pacific
- Red-tailed tropical bird ( Phaethon rubricauda ), 45–90 cm long, lives in the Indian Ocean and the Pacific
Humans and tropical birds
While the German name Tropikvogel merely refers to the tropical home of these birds, English-speaking seafarers in particular have given the tropical birds more imaginative names. The most widespread is the name bosunbird ( bosun = " boatman "), presumably because of its call, which is reminiscent of the trilling of a boatswain's whistle . The names marlinspike (= " Marlspieker ") and strawtail ("straw tail") refer to the shape and appearance of the long tail feathers. They were also called noddys ("sleeping hats ") because they were easy to catch. After all, the generic name Phaethon is derived from Phaëthon , the son of the god Helios in Greek mythology , who was allowed to pull the sun chariot across the sky for one day.
Tropical birds have always been used by the inhabitants of tropical islands. Polynesians often used the feathers as ornaments, and Caribs ate the animals' eggs and meat. Even today nests are looted in some places. The tropical bird colonies on Christmas Island were almost destroyed by egg robbery, but have been recovering since the introduction of protective laws in 1977.
A much greater threat to tropical birds are ground predators . The islands on which these birds breed are often so remote that no mammals were to be feared. Seafarers later abandoned cats and rats there, with devastating consequences for the local fauna. On such islands, breeding only succeeds on inaccessible cliffs. A study on the Kure Atoll has shown that in some years 100% of the eggs and young fall victim to the Pacific rat .
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 .
- Bryan Nelson : Pelicans, Cormorants and their relatives. Oxford University Press, 2005, ISBN 0-19-857727-3 .
Individual evidence
- ↑ Per GP Ericson et al .: Diversification of Neoaves: integration of molecular sequence data and fossils . Biol. Lett. doi : 10.1098 / rsbl.2006.0523
- ↑ Hackett et al .: A Phylogenomic Study of Birds Reveals Their Evolutionary History . Science 27 June 2008: Vol. 320. no. 5884, pp. 1763–1768 doi : 10.1126 / science.1157704
- ^ Frank Gill and Minturn Wright: BIRDS OF THE WORLD Recommended English Names. Princeton University Press, 2006, ISBN 0-7136-7904-2
- ↑ WorldBirdNames.org IOC World Bird List ( Memento of the original from July 24, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ AOU Committee on Classification and Nomenclature (North & Middle America) Proposals 2008-C (PDF; 109 kB)
- ↑ Dea Birkett: Snake in Paradise. My trip to the South Seas to the descendants of the mutineers on the Bounty . Munich 1999, p. 209.
