Bare-eyed cockatoo
| Bare-eyed cockatoo | ||||||||||
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Bare-eyed cockatoo |
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| Cacatua sanguinea | ||||||||||
| Gould , 1843 |
The black-eye cockatoo ( Cacatua sanguinea ), also known as the red-bridled cockatoo , is a common and widespread species of parrot in Australia that belongs to the cockatoo family. It is characterized by the short tail, the rear-facing feather hood and the proportionally small beak. In addition to the root cockatoo and the nasal cockatoo, it is the third so-called Corella species that occurs in Australia. The basic color of the plumage is white. However, their plumage is often heavily soiled with red soil as they dig in the ground while foraging.
Naked-eye cockatoos are one of the species of cockatoo that has benefited from the development of the Australian continent by European settlers. The installation of cattle troughs also enabled them to colonize regions that previously offered too little water to be inhabited by them all year round. Today they are represented in several, separate populations on the Australian continent. A total of four subspecies are described for this species. In some regions, hairless cockatoos have increased so much that they are considered pests. They are therefore shot by some farmers in Western Australia to prevent crop failures.
The hairless cockatoo is believed to be the first species of Australian parrot to be described by a European. The English traveler William Dampier arrived on August 22, 1699 on one of the smaller islands off the west coast of Australia and later reported on some white parrots that he had seen. Naked-eye cockatoos are the only white cockatoos that live on the island he visited.
Appearance
Naked-eye cockatoos reach a body length of 38 centimeters and weigh between 480 and 800 grams. Naked-eye cockatoos belong to the so-called "white cockatoos": The basic color of their plumage is consistently white in the nominate form . Only the outer control springs are yellow towards the base and on the underside of the inner flags. There are subspecies whose head, neck and breast feathers have a light pink-orange color.
The spring bonnet is short and consists only of elongated springs on the front apex. The rein is pale pink. The featherless eye area is grayish blue. The iris is dark brown. The beak is small and horn-colored. The legs are gray. There is no gender dimorphism .
The flight of the bare-eyed cockatoos is fast with flat wing beats. The flight is interrupted by short gliding phases and is similar to the flight of pigeons. During the call, a three-syllable, chuckling körr-ör-rap ... körr-ör-rap can be heard, the pitch of which rises sharply at the end. Excited birds make harsh screeching noises. These harsh calls are very audible near sleeping trees.
distribution and habitat
Naked-eye cockatoos are disjoint in the west, north and east of Australia. They are also found in southern New Guinea. They are introduced in Tasmania.
Naked-eye cockatoos are dependent on permanent water points, but otherwise colonize a variety of different habitats. This includes forest areas in the coastal regions of Australia as well as arid and semi-arid areas inland. The habitats that they inhabit include grasslands, arable land, tree savannahs, sedge plains, mangroves, rice fields, gallery forests and moist hardwood forests . Feral populations can also be found in the coastal lowlands. The species has also adapted very well to urban habitats and occurs in the vicinity of large cities.
Basically, bare-eyed cockatoos seem to live very nomadically in the interior of Australia. They are only true to their location during the breeding season. Naked-eye cockatoos that colonize coastal regions or coastal landscape zones, on the other hand, are very faithful to their location. One of the regions in which hairless cockatoos have increased significantly is the Wheatbelt region . Their spread is not without effects on other cockatoo species. They are particularly strong competition for root cockatoos and seem to displace them in newly settled regions.
behavior
Naked-eye cockatoos can form very large flocks. A swarm is documented that stayed near Sandringham Station in southwest Queensland in August and September 1980 . It has been estimated at more than 6,000 individuals. When the cockatoos ate on the ground, they spread over a length of more than a square kilometer. In doing so, they severely damage the resting and sleeping trees. Since the cockatoos like to nibble on the foliage when they are resting, the trees are often completely defoliated. But there are also indications of significantly larger swarms. In the 1970s, a flock of hairless cockatoos is said to have consisted of 60,000 to 70,000 individuals. And after a food shortage in the 1980s, a swarm was observed in Western Australia that consisted of more than 32,000 individuals.
The ornithologist Joseph M. Forshaw , who specializes in Australian parrots , points out that these large swarms come about because the natural swarming has increased as a result of the abundance of food on agricultural land. As a rule, they have an abundant supply of food when perennial grasses are sown in the period from May to October. Large swarms that wander far and wide are typical at this time. They disperse in smaller swarms as soon as these feeding grounds are used. These only comprise a few hundred copies and are then much more sedentary. In agricultural regions where sorghum is cultivated all year round , this seasonal rhythm does not apply, so that the swarms last longer.
Naked-eye cockatoos are generally diurnal birds. However, they leave their sleeping trees before sunrise, which are preferably found near water holes. They first drink and then fly in a swarm into the feeding grounds. Swarms feeding on the ground move in one direction. The cockatoos located at the end and in the middle of the flock keep flying up to settle at the head of the flock. During the hottest part of the day, they take shelter in the shade of the foliage of trees and shrubs. They behave very destructively, biting off the leaves or peeling off the bark of the branches. Food intake has a second peak in the late afternoon. They then find themselves again at a watering place to drink and return to their sleeping trees at sunset.
Exuberant play behavior has been observed and described several times in naked-eye cockatoos. The most noticeable behaviors include lying on their backs and turning and turning branches or stones with their feet up.
food
Naked-eye cockatoos eat grass seeds, the seeds of herbaceous plants, nuts, fruits, berries, roots, buds, flowers as well as insects and their larvae. Most of the food is taken up on the ground. While searching for food, they dig holes up to two inches deep. As a result, the underside of the body in particular is heavily smeared with earth. They eat crops like rice and millet . However, they also ingest large quantities of the seeds of Emex Australia , a plant that is considered a weed that has spread rapidly as a result of increasing grazing and is considered a serious plague. For this reason, they are under protection in parts of northwestern Australia.
Reproduction
As far as we know today, bare-eyed cockatoos are monogamous birds whose pairing does not end until one of the partners dies. The breeding season of the bare-eyed cockatoos varies greatly. It depends on the respective distribution area and is determined by climatic conditions. At the beginning of the breeding season, sexually mature couples break away from the swarm and pursue the breeding business apart from the swarm life. The courtship behavior is simple, as with many other cockatoo species. The males strut towards the females with their bonnets erect and their feathers fanned out and bow to her calling out.
Naked-eye cockatoos are cave breeders. Breeding trees are usually located near water points or on rivers. As a rule, bare-eyed cockatoos prefer high tree hollows. There is also evidence of nesting for crevices on steep walls and broken termite structures. The clutch consists of two to four eggs. The laying interval is 1.5 to 2 days. The incubation period is 26 days. Both parent birds breed. The young birds stay in the nest box for about eight weeks. After leaving the breeding cave, they are fed by the parent birds for about six to seven weeks.
Similar to the Inca cockatoo , the bare-eyed cockatoo also has mixed layers with pink cockatoos. Due to the strong competition for suitable nesting holes, nude-eyed cockatoos occasionally displace pink cockatoos from their nest, but incubate their eggs together with their own. They then raise this mixed brood as well.
Naked-eyed cockatoos in human care
Naked-eye cockatoos are considered hardy birds that thrive very well in human care. As early as 1907, one of the first breeds succeeded in the London Zoo. The San Diego Zoo raised more than 50 fledglings between 1933 and 1966 with just one breeding pair. They are among the most talented cockatoos and are therefore popular aviary birds in Australia. The Australian government's ban on the export of native animals in the 1960s means that hairless cockatoos are kept relatively infrequent outside of Australia. For their well-being they need spacious all-metal aviaries with sturdy wire mesh. Because of their aggressive behavior, they cannot be kept with other cockatoos.
supporting documents
Individual evidence
- ↑ a b Hoppe, p. 173.
- ↑ a b Forshaw, p. 203.
- ↑ a b Forshaw, p. 198.
- ↑ Hoppe, p. 171.
- ^ Forshaw, p. 196.
- ^ Forshaw, p. 205.
- ↑ a b Hoppe, p. 177.
- ↑ a b Forshaw, p. 204.
- ↑ Hoppe, p. 174.
- ^ Forshaw, p. 206.
- ↑ a b Hoppe, p. 178.
- ^ Forshaw, p. 207.
- ↑ Hoppe, p. 179.
- ^ Forshaw, p. 209.
- ↑ Hoppe, p. 180.
literature
- Joseph M. Forshaw , illustrated by William T. Cooper: Australian Parrots. 1st German-language edition. Volume 1: Cockatoos and Lories. Arndt-Verlag, Bretten 2003, ISBN 978-3-9808245-1-4 .
- Dieter Hoppe : Cockatoos - way of life, keeping and breeding. Eugen Ulmer Verlag, Stuttgart 1986, ISBN 3-8001-7155-4 .
Web links
- Cacatua sanguinea onthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved December 26, 2013.