Australian darter

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Australian darter
Male Australian darter

Male Australian darter

Systematics
Class : Birds (aves)
Order : Suliformes
Family : Darter (Anhingidae)
Genre : Darter ( anhinga )
Type : Australian darter
Scientific name
Anhinga novaehollandiae
( Gould , 1847)
Female Australian darter

The Australian darter ( Anhinga novaehollandiae ) is a species of the darter (Anhingidae). Its range includes large parts of Australia and New Guinea .

The IUCN lists the Australian darter as currently safe ( least concern ).

Appearance

When fully grown, the Australian darter reaches a body length of about 86 to 94 cm and weighs between 900 and 2000 g. The wingspan is 120 cm.

The Australian darter is a dark-feathered fish eater with a very long neck, which is very similar to the other three species of darter . Characteristic of the Australian darter is a brownish to black-brownish head, the back is glossy black with conspicuous white, silver-gray or pale brown stripes and spots. The control feathers are long and brownish, but rather blackish in newly molted birds. A noticeable white or pale brown stripe runs from the base of the beak along the sides of the head and the upper neck. The genders are also clearly identifiable when observing the field. Males have a dark underside of the body while that of females is light. Females also have a gray-brown upper body, but have similar color markings as the males. The iris is light yellow to yellow during the breeding season, and pale yellow to pale brown outside the breeding season. The beak is as with the other Anhinga mm TYPES with 71-87 quite long (longer than the head), slender and tapered. However, with an average of 75 mm, the beak length is slightly shorter than that of the other three species. The Australian darter often swims in such a way that only the neck and head are visible above the water. Due to the specially formed vertebrae in the neck, he is able to bend his neck in a z-shape and to stretch it jerkily. He uses this to spear fish with his beak. This ability has earned him the common name Australasian darter .

distribution and habitat

The Australian darter occurs all over Australia except for the waterless areas in the interior of the continent. New Guinea and neighboring smaller islands are also part of its range. Perhaps the darter on Timor also belongs to this species. Stray visitors occasionally also reach New Zealand. The migratory movements of Australian darters have not yet been conclusively investigated, but one ringed bird was found over a distance of more than 2000 kilometers from the ringing site. In the north of the Australian Northern Territory , the population on the Alligator River is very high in the winter dry season, but numerous birds leave this region in the rainy season. In the Australian state of Victoria, on the other hand, there is no evidence of comparable migration.

Its habitat are inland wetlands and protected coastal areas in the tropics and subtropics. For its food search it is dependent on open, large bodies of water without large waves and needs branches or dead tree trunks protruding above the water surface in order to rest on it and to dry its wings. It occurs accordingly in lakes, reservoirs, ponds, billabongs , swamps and river meanders. He avoids water regions with dense aquatic vegetation. On the other hand, the composition of the riparian vegetation is not decisive for whether a body of water offers a suitable habitat for it.

Food and foraging

Australian darter on a successful hunt on the Cooks River, New South Wales, Australia

The food spectrum of the Australian darter consists mainly of fish, as with the other darter species. They also eat insects and other animals in the water zone such as turtles. Most of their food is found diving. They prefer to use waters with a depth of more than 60 centimeters while foraging. The individual dives last 30 to 60 seconds.

Small prey is swallowed underwater. Fish are speared with the beak and brought to the surface of the water. With a quick head movement, the fish is thrown onto the surface of the water, picked up again and swallowed head first. Occasionally they also throw the fish in the air and catch it again before it hits the surface of the water. Large fish are occasionally taken to a resting place and eaten there.

Reproduction

Australian darters enter into a monogamous couple relationship that lasts for at least one reproductive period. They nest either individually or in loose colonies of up to ten nests. Other tree-breeding waterfowl such as cormorants, spoonbills and ibises are often found in these colonies. A radius of several meters around the nest is defended against conspecifics. In contrast, they do not defend any food territory.

The male chooses the nesting site, occasionally choosing a previously used nesting site. The territory around the nest can be limited to the branch on which the nest is located or the entire tree in which it is incubated. Part of the antagonistic behavior of Australian darters is that they point at an intruder with their bills closed. When it comes closer, the beak is opened slightly and the bird makes hissing noises. Non-breeding birds occasionally approach with open bills and spread wings, and they call very loudly. If the intruder gets even closer, they snap at him, but they do not aim at direct physical contact, the beak is only quickly closed near the head or neck. Only when the intruder is not deterred by this does the Australian darter, which is defending its territory, also peck at the neck or head of the intruder.

The Australian darter has a fairly variable breeding season due to its range, which extends from the southern temperate zones of southern Australia to the tropical areas of northern Australia and New Guinea. There are one or, in rare cases, two broods per year. The breeding season in South Australia is in spring (August to October), in northern Australia in the rainy season (January to March / April), in April in the Trans-Fly region in southern New Guinea, in August and September in the Lower-Fly region and in July and November in the area of ​​the capital Port Moresby . In some regions it is absent as a breeding bird for a long time. The nest base is usually fresh branches, with the nest erected on top of it, up to 150 dry branches that are between 10 and 40 centimeters long are built. Some nests are so loose in their structure that the eggs are visible to an observer standing directly below the nest. The nesting material is mainly brought in by the male.

The clutch comprises between two and six eggs, but clutches that consist of four eggs are typical. Both parent birds breed, the brood is taken with the first egg. The breeding season averages 28 days, the hatching of the young is asynchronous. Newly hatched chicks are initially naked. Nestlings are usually the size of their parent birds by four weeks of age. At this age, they also begin to climb out of the nest and occasionally even swim. Some of the young birds climb back into the nest, others stay on branches below the nest. At around 50 days old they can fly short distances. The age at which nestlings usually fledge is not entirely certain. It is believed that they fledge at around 60 days.

The reproductive success of the Australian darter has not yet been systematically investigated. At Lake Cowal in Australia, 38 clutches of 122 nests were lost. Most of the losses are due to human interference. Breeding Australian darter usually do not return to their nests until the disturbers have withdrawn from the area. New Holland crows usually take advantage of this break in brood to eat the eggs. In 64 nests between two and five young birds hatched per nest, in twelve cases a pronounced difference in size due to the asynchronously hatching young birds meant that the smallest nestling did not survive. In fourteen cases, nestlings died after injuring themselves jumping out of the nest.

Systematics

From top left to bottom right: Indian, African and Australian darter, each with clearly visible light cheek stripes, American darter without cheek stripes

The Australian darter is part of the darter family (Anhingidae) and is closely related to the African darter ( Anhinga rufa ) and also to the Indian darter ( Anhinga melanogaster ). These three species have long been thought of as a single species of Old World darter ( Anhinga melanogaster ). Genetic distance and morphological differences between the three species are of a similar order of magnitude as in typical cormorant species or gannet species , which also belong to the order Suliformes. A division of the species therefore seems justified based on the current status (2018).

The American darter differs more clearly from these three species, especially in the plumage due to the lack of the light cheek stripe.

There are two subspecies of the Australian darter:

  • Anhinga novaehollandiae novaehollandia , ( Gould , 1847) - Australia
  • Anhinga novaehollandiae papua , Rand , 1938 - New Guinea and possibly Timor

literature

  • 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

Commons : Australian Darter  album with pictures, videos and audio files

Single receipts

  1. ↑ a b c Higgins, p. 799
  2. ↑ a b c d Schodde, R., Kirway, G., Porter, R .: Morphological differentiation and speciation among darters (Anhinga) Bulletin of the British Ornithologists' Club vol. 132, 2012, No. 4, pp. 283-294
  3. ↑ a b c del Hoyo, J., Collar, N. & Garcia, EFJ (2018): Australasian Darter (Anhinga novaehollandiae). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, DA & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. ( https://www.hbw.com/node/467296 , accessed July 30, 2018).
  4. ↑ a b c d Higgins, p. 801
  5. ↑ Higgins, p. 803
  6. ↑ Higgins, pp. 801 and 802
  7. ↑ Beruldsen, Gordon: Australian Birds: Their Nests and Eggs . Ed .: self. Kenmore Hills, Qld 2003, ISBN 0-646-42798-9 , pp. 192-93 .
  8. ↑ Bruce M. Beehler, Thane K. Pratt: Birds of New Guinea: Distribution, Taxonomy, and Systematics . Ed .: Princeton University Press. 2016, ISBN 978-1-4008-8071-3 , pp. 122 ( google.com ).
  9. ↑ a b c Higgins, p. 804
  10. ^ List of bird names in the IOU IOC World Bird List