Haircocks
| Haircocks | ||||||||||
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Hairy scuba diver ( Poliocephalus poliocephalus ) |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Poliocephalus poliocephalus | ||||||||||
| ( Jardine & Selby , 1827) |
The hoary-headed grebe ( poliocephalus poliocephalus ) is a species of bird in the family of grebes (Podicipedidae). This species belongs to the fauna of Australia and is also found in Tasmania . The behavior of the scapula differs somewhat from that of other grebes. It flies more frequently than the other species and is considered both the least reputable and the most sociable within this family. It breeds in colonies with up to 400 nests, and outside of the breeding season, schools of thousands of hairdressers can be found. While other species of grebes such as the great crested grebe and racing divers have distinctive and sometimes spectacular courtship behavior for humans, courtship is relatively easy.
The IUCN classifies the poppy diver as not endangered ( least concern ).
Appearance
When fully grown, haircocks reach a body length of 29 to 31 centimeters and then weigh about 250 grams. This species has no sex dimorphism . Only the dark beak with the light tip is slightly longer in males than in females. Both males and females have white, hair-like feathers on their heads and upper necks, which are eponymous in their splendid dress. In contrast, these are missing in the plain dress. The coat is gray-brown in all clothes, the back is darker and the rump is whitish. The iris is black-brown, the legs and feet are gray-yellow.
There is a possibility of confusion with the Australian Little Grebe and the Maori Diver, which only occurs in New Zealand . In the splendid plumage, the haircap can be distinguished from both species by its striking head plumage. With young birds and adults in simple dress, the possibility of confusion is very high, especially with the Australian little grebe. In general, the shank diver is grayer on the flanks than the Australian little diver, the shallow diver is also not very shouting, while the Australian little diver is often heard high, trilling calls. The Maori diver is generally darker than the haircap diver and, above all, has very conspicuous yellow eyes that contrast strongly with the dark head.
In contrast to the Australian little grebe, the poppy diver flies up relatively frequently. Large troops are often very restless, parts of the troop keep flying up, especially at dusk.
distribution and habitat
The hair diver is found in all Australian states. It is particularly common in the southeast and southwest of Australia and Tasmania. In general, it is absent in the dry interior of Australia, but it can colonize all bodies of water of sufficient size that exist for a long time after rainfall.
The poppy diver was first observed in New Zealand in 1975. Since then, one and occasionally two individuals of this species have been seen in widely separated places. Repeated observations at the same site are rare, however, haired divers breeding successfully at Lake Te Anau in 1975/1976 . Two young birds hatched and one of them survived to fly out. Up to 1978 there were repeated broods of up to two breeding pairs, after 1978 no further broods were found at this lake.
The hairdresser's habitat is inland wetlands and estuaries. It is a very adaptable species that colonizes a number of temperate and tropical regions in Australia and is also found in arid and semi-arid regions. Its height distribution ranges from sea level to altitudes of 1000 meters. It prefers large, open bodies of water, but can also colonize bodies of water less than one hectare in size and can also be found in bodies of water that only exist for a short time. Waters with a depth of 0.5 to 3 meters and extensive underwater vegetation offer ideal habitats. It can also be observed relatively frequently in water retention basins. In general, the construction of large cattle troughs and reservoirs has promoted its spread in regions that otherwise only offer inadequate living conditions. During the Australian winter in particular, they use wetlands on the coast and are then occasionally seen in large numbers in bays and lagoons, in mangrove swamps and salt pans.
The migratory movements of the paddock have not yet been adequately investigated. In the arid regions of its range, the haircuff is extremely dismigratory . The colonization of New Zealand in the second half of the 20th century also suggests that haircocks can go on long migrations. In the coastal areas it shows rather regular migration movements.
Food and diet
The main food of the hairdresser are aquatic invertebrates, which he catches mainly by diving. The diving process is initiated by a powerful, somewhat awkward-looking jump forward. Dives for an average of 17.5 seconds, between the individual dives you are back on the water surface for an average of nine seconds. They eat less frequently than other small grebes on the surface of the water. Occasionally they swim in a circle with their heads submerged, which is believed to help startle prey. Occasionally they are associated with other herbivorous water birds while foraging. It is very likely that they will find more prey, which these birds foraging for food startle off.
Social behavior and reproduction
Outside the breeding season, the haircap can be seen in small groups or in large troops of several thousand individuals. Such large troops are often divided into smaller groups that swim close together. Individual shells and small groups are more often associated with Australian little divers. Even during the breeding season, haircocks are sociable birds that breed in colonies with up to 400 nests. Antagonistic behavior towards conspecifics is mainly limited to swiftly swimming towards each other, with the neck stretched far forward.
Haircocks enter into a monogamous relationship, but there is no evidence that the relationship has lasted for more than one reproductive period. Couple relationships in non-brooding troops also seem to have a short duration. The pairing at the beginning of the reproductive period is not yet very stable, at the beginning of the nest building males often mate with females outside of their mating relationship.
literature
- Jon Fjeldså: The Grebes . Oxford University Press, 2004, ISBN 0-19-850064-5
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683
Web links
- Videos, photos and sound recordings about Poliocephalus poliocephalus in the Internet Bird Collection
- Poliocephalus poliocephalus inthe IUCN 2013 Red List of Endangered Species . Listed by: BirdLife International, 2012. Retrieved January 29, 2014.