Australian booby
| Australian booby | ||||||||
|---|---|---|---|---|---|---|---|---|
Australian booby |
||||||||
| Systematics | ||||||||
|
||||||||
| Scientific name | ||||||||
| More serrator | ||||||||
| ( GR Gray , 1843) |
The Australian gannets ( Morus serrator ), also Austral boobies called, is a nearly geese large seabird from the family of boobies . In its appearance it is reminiscent of bass and cape boobies . Within the gannet family, it is the furthest south-breeding species. Despite its name, the Australian gannet belongs to the fauna of New Zealand rather than to that of Australia : the far greater number of breeding colonies and individuals can be found in New Zealand.
Appearance
The Australian booby reaches a height of 84 to 91 centimeters. The wings have a length of 44 to 48.5 centimeters. The wingspan is between 170 and 200 centimeters. When fully grown, they weigh between 2 and 2.8 kilograms.
The body plumage of the adult Australian booby is predominantly white. The head and neck are covered with yellow, although the yellow birds vary from season to season. The wings, the wing-coverts and the central tail feathers are black except for the first wing. The beak is blue-gray and separated from the head plumage at the base of the beak by black, featherless skin. The eyes are gray with a blue eye ring. The legs are black and gray. Young birds are predominantly gray-brown feathered.
Basically, boobies are not to be confused with other birds. Although the Australian Gannet is very similar to other booby species, which is very similar gannets but does not occur in the southern hemisphere and the Cape Gannet reached the Australian continent only as Irrgast. Individual Cape gannets have been detected several times in a bay near Port Phillip in breeding colonies of the Australian gannet and ringed Cape gannets have been caught off the coast of Western Australia in South Africa. Since the cape booby can only be distinguished from the Australian booby up close, it is possible that cape boobies reach Australia relatively regularly.
Existence and distribution
The Australian booby is the second rarest booby species after the gray-footed booby . The number of breeding pairs is estimated at 70,000 to 75,000. The breeding area is between 32 ° 12 'S to 46 ° 36' S. 99 percent of the world population, however, breeds in a zone from 34 ° to 40 ° S. Like the two sister species Northern Gannet and Cape Gannet, the Australian gannet uses cool, but nutrient-rich seawater regions.
Small breeding colonies of the Australian gannet can be found on the south and east coast of Australia as well as on the coast of Tasmania. Most of the breeding colonies are on the coast of New Zealand. Three breeding colonies are located on the New Zealand mainland, the rest on small islands off the New Zealand coast.
After the breeding season, the adult Australian gannets leave the breeding colonies for a period of three to four months. During their first three to four years of life, young birds migrate to regions that are several thousand kilometers away from their breeding colonies.
Reproduction
The mode of reproduction of the Australian gannet is well known from several years of studies. The subjects of study were several larger breeding colonies off the New Zealand coast. Australian boobies raise only one clutch per year, but regularly lay replacement clutches if either the clutch is lost or the young bird dies before its eighth day of life. There can be layovers as early as eight days after the clutch has been lost. The longest observed interval between the loss of a young bird and the laying of a new egg was 34 days. In this case, the young bird died at the age of five days. Eggs are lost, among other things, because Australian boobies are barely able to retrieve an egg that has rolled out of the nest.
The breeding colonies can be very small and comprise only two nests. As a rule, however, a larger number of breeding pairs are gathered, and large colonies consist of up to 8,000 nests. The breeding colonies are usually located on islands with cliffs; no other species usually breed in the colonies. The breeding season generally falls between July and February. Basically, Australian boobies choose flat sections on hard-to-reach islands with cliffs as their nesting site. Usually the nests of a colony cover the highest parts of the island. The site usually has no vegetation as the birds trample it and the amount of guano causes the plants to die. The oviposition within the breeding colony is not synchronized. In a colony observed off the New Zealand coast, the egg-laying period extended over 13 weeks.
The nests consist of seaweed, grass, earth and flotsam of all kinds. The nesting material is mainly collected by the male. This hands over the nesting material to the female who builds it. They regularly steal nesting material from unoccupied nests in the neighborhood. The nests are rebuilt every year, as the weather during the winter season destroys the nests of the previous year, with the nest being built over the entire breeding period. Among other things, the edge height of the nest increases, as Australian boobies settle the breeding season through excrement on the edge of the nest. The nests are on average about 10 to 20 centimeters high.
The clutch consists of only one egg. This is elliptical to oval in shape. The surface is matt and rough. Freshly laid eggs are pale blue at first and turn white as they dry. Both parent birds breed, but the female's share of the breeding business is somewhat larger. The breeding season averages 44 days. The parent birds incubate the egg by embracing it on both sides with their webs that are well supplied with blood.
Freshly hatched young birds initially close their eyes for two to three days. In the beginning they are hardly feathered and are only densely covered with about one centimeter long dunes when they are around two weeks old. They have only completely lost their downy plumage when they are 80 to 94 days old. The young birds of the Australian gannet grow up very quickly. At the age of three weeks they have already reached a size at which they are not completely covered by the parent birds when they huddle. While huddling, the young birds sit on their parent birds' webbed feet.
The care of the young bird ends when it leaves the nest. Australian gannet fledglings are normally fledged at 107 to 109 days. Young birds seek out the edge of a cliff or a steep slope and fly off from there. They breed for the first time when they are four to seven years old.
Australian boobies in the breeding colonies investigated in New Zealand reached an average age of 20 years. As a rule, a breeding pair raises 15 young birds during their lifetime, but 13 of these die before they brood themselves. The predators of the Australian booby include various species of gull, which mainly eat the eggs.
Systematics
It is generally accepted knowledge to assign the species of the booby family to the three genera Morus , Sula and Papasula . Within this classification, the Australian gannet belongs to the genus Morus, along with Cape gannets and Northern gannets . The following cladogram gives the results of the molecular analysis by Friesen and Anderson, which confirm this division:
| Sulidae (boobies) |
|
||||||||||||||||||||||||||||||||||||||||||||||||
|
|
The ornithologist Bryan Nelson has suggested that the Cape gannet and the Australian gannet be regarded as allospecies of the superspecies northern gannet . The Australian gannet differs from the Cape gannet only in a slightly smaller, featherless area around the eyes, a darker iris and the black color of the four central tail feathers. Hybridization with Kaptölpeln occurs occasionally.
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 (Eds.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0-19-553068-3
- Bryan Nelson : The Atlantic Gannet. Fenix Books, Norfolk 2002.
- Bryan Nelson: Pelicans, Cormorants and their relatives. Oxford University Press, 2005, ISBN 0-19-857727-3 .
- Hadoram Shirihai: A Complete Guide to Antarctic Wildlife - The Birds and Marine Mammals of the Antarctic Continent and Southern Ocean . Alula Press, Degerby 2002, ISBN 951-98947-0-5
Single receipts
- ^ Shirihai, p. 207
- ^ Higgins, p. 752
- ^ Higgins, p. 749
- ↑ Nelson, 2005, p. 291
- ^ Higgins, p. 754
- ^ Higgins, p. 759
- ↑ a b c d e f Higgins, p. 760
- ^ VL Friesen, DJ Anderson: Phylogeny and evolution of the Sulidae (Pelecaniformes: Aves): a test of alternative nodes of specification. In: Molecular Phylogenetics and Evolution 1997, No. 7, pp. 252-260
Web links
- More serrator onthe IUCN Red List of Threatened Species .
- Videos, photos, and sound recordings for More serrator in the Internet Bird Collection
- www.xflo.net, June 2014, Florian Wizorek: The Boobies from Cape Kidnappers (photo documentation of the Australian booby colony from Cape Kidnappers in New Zealand)