Nosed cockatoo
| Nosed cockatoo | ||||||||||
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Nosed cockatoo |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Cacatua tenuirostris | ||||||||||
| ( Kuhl , 1820) |
The nasal cockatoo ( Cacatua tenuirostris ) is a species of parrot native to Australia. Together with the bare-eyed cockatoo and the root cockatoo , it is classified as one of the so-called "Corellas". Nasal cockatoos were originally only common in southeastern Australia.
The species was considered critically endangered in the 1950s. The population was less than 1,000 birds. After myxomatosis significantly reduced the rabbits introduced into Australia and thus eliminated a major food competitor, the number of nasal cockatoos has recovered significantly. As a result of captive refugees, nasal cockatoo populations can now be found in all Australian states. These captive refugees are mainly due to an attempt by an Australian authority to use trapping operations to reduce the number of nasal cockatoos in regions where the numbers of nasal cockatoos had recovered so much that they were increasingly considered pests. The captured birds should be sold to private owners. However, wild-caught animals turned out to be so unsuitable for keeping pets that they were released in many places.
Appearance
Nasal cockatoos reach a body length of 37 centimeters. They weigh between 480 and 650 grams.
Nasal cockatoos do not exhibit sexual dimorphism . The basic color of the plumage is white. The spring bonnet is relatively small and consists of springs of the front apex, which are elongated. The orange to orange-red areas on the head and throat are striking. A narrow area above the beak, the so-called headband, the reins, the front part of the eye ring and a crescent-shaped area of the throat are bright orange. The bare eye ring is surrounded by a yellow-orange spring band. The featherless area around the eyes is pale grayish blue. Similar to the bare- eyed cockatoo and the burrowing cockatoo , the featherless part under the eye is slightly extended downwards.
The feathers on the front back and chest to the upper abdomen are pale pink-orange at their base. The balance springs and the outer control springs are predominantly white. They become yellowish towards the base. The inner lugs on the underside are also pale yellow. The beak is horn-colored. The upper beak is noticeably elongated. The iris is deep brown. The legs are gray and the toes are dark gray.
Young birds are very similar to adult birds. However, the orange colored areas on the head and neck are less pronounced. The upper beak is a little shorter than that of adult, sexually mature nasal cockatoos.
The flight of the nosed cockatoo is quick with a flapping wing beat. The flight is repeatedly interrupted by short phases in which the nasal cockatoos glide with downward curved wings. During the flight, nasal cockatoos emit a high-pitched , fistulous kurr-ur-rup ... kurr-ur-rup as a contact call. The calls of the nasal cockatoos sound unpleasant to human ears. They are also very loud, so they are usually heard rather than seen.
Distribution and population development
The natural range of the nasal cockatoo extends from the extreme southeast of South Australia to the center of Victoria and the southwest of New South Wales . Occasionally, a larger natural range is indicated in the literature. However, this results from confusion with the very similar bare-eyed cockatoo .
Before the colonization of Australia, the distribution area was larger according to today's knowledge. The increasing pasture economy as well as the introduced rabbits restricted the food sources of the nasal cockatoos, as this changed the ground vegetation permanently. The keeping of sheep had a particularly negative effect , while in regions where mainly cattle were kept, even larger numbers of nasal cockatoos existed. Due to the dwindling food resources, nasal cockatoos switched to grain as a substitute food. Farmers responded by shooting the birds and laying poison baits. This led to the complete extermination of the nasal cockatoos locally in the 19th century. In the 1950s only remnants of the population existed, so that an extinction of the species had to be feared. In the 1950s, myxomatosis broke out in the rabbit population and the rabbit population collapsed suddenly. The most serious food competitor, the nasal cockatoos, was reduced to such an extent that the numbers rose again from the 1950s onwards. Nose cockatoos also benefited from increasing in Australia entrained plants such as onion grass ( Romulea rosea ) and cultivated plants such as the various cereals and sunflowers . The increase in the population of the nasal cockatoos was so strong over the next three decades that problems arose again in the heavily agricultural regions as early as the 1980s. Selective surveys make it clear how dramatic the recovery was in some cases: In a region in South West Australia, only 182 nasal cockatoos were counted in October 1974. Only ten years later, the regional population comprised 250,000 individuals. In the meantime, nasal cockatoos are populating again in regions where they have not occurred in the last hundred years.
habitat
The habitat of the nasal cockatoos are grass savannahs at altitudes below 400 meters above sea level and with annual rainfall between 250 and 800 millimeters. Precipitation is mostly limited to the winter half-year. They prefer slightly more humid vegetation zones than their closest relative, the bare-eyed cockatoo .
Nose cockatoos can now also be found in large numbers in the vicinity of cities. According to ornithologist Joseph M. Forshaw , who specializes in Australian parrots , these captive refugees are largely the result of two failed catches by the South Australian National Parks and Wildlife Service in the 1970s and 1980s. In both trapping campaigns, nasal cockatoos were caught in agricultural regions, ringed and then taken to the inner Australian bird trade. The trapping carried out in the 1980s was the major trapping operation. The wild-caught animals proved to be completely unsuitable for keeping pets and were released into the wild in large numbers by buyers and traders. In this way, nasal cockatoos have been shown to establish themselves in the vicinity of Perth, a region that had never been part of their range. Their spread in these regions is viewed critically because they represent a nesting site competition with the cockatoo species endemic there. There are also crosses with the closely related Wühlerkakadu in the wild .
The spread of nasal cockatoos in urban areas is not without problems. With their loud cries, they represent a considerable nuisance for the residents. They also rummage through parks, sports facilities and golf courses in search of food.
behavior
Cockatoos are birds that generally live in flocks. Only nesting pairs do not move in swarms, but rather stay near their nesting cavity during the breeding season. This means that the swarm size fluctuates greatly over the course of the year. In a study area in the extreme southeast of South Australia, for example, the mean swarm size in September was 29 individuals; in May, however, 249 individuals. During the times when most of the grain seeds are germinating and the sunflowers are ripening, nasal cockatoos occasionally team up with pink and yellow-crested cockatoos . In these flocks, nasal cockatoos benefit from the very attentive behavior of the yellow-crested cockatoos, similar to the pink cockatoos. These have a guard system in which a few birds stay in the treetops and watch the environment, while the others look for food on the ground. Nose cockatoos also have a guard system. However, nasal cockatoos remain on the ground.
Nasal cockatoos are diurnal birds that leave the sleeping tree at dawn. They then first look for a watering hole before they fly further into the feeding grounds. While the birds spend the whole day feeding in winter, they take longer breaks in the summer months during the hottest part of the day. They then seek shelter from the sun in the foliage of trees. As resting trees, they prefer to seek out those that are close to water.
food
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Nasal cockatoos look for food almost exclusively on the ground. They either look for seeds on the surface of the soil or dig for roots and tubers. The swarm continues to move as it feeds, as nasal cockatoos rest at the end of the feeding swarm and settle down again at the head of the swarm. Since nasal cockatoos literally dig up the ground during their foraging, their swarms are often accompanied by insectivores.
Originally, the nasal cockatoos' diet consisted mainly of the Australian plant Microseris lanceolata . This has changed a lot since then. Ninety percent of their diet comes from plants deliberately or accidentally introduced into Australia. The adjustment in diet is due to the fact that native plants have been pushed back through clearing, introduced rabbits and the expansion of pasture farming. In addition to the introduced onion grass, a type of pseudo crocus , nasal cockatoos now mainly feed on rice , oats and sunflowers .
Reproduction
Nose cockatoos have a slightly more elaborate courtship behavior than most other cockatoos. Males woo their female by scratching her plumage and feeding her before attempting copulation. As a further courtship gesture, males strut towards the female with spread wings and then turn away from her again. This courtship gesture also ends with attempts at copulation.
Cockatoos are cave breeders. Most of the nests are created in the eucalyptus species Eucalyptus camaldulensis . The minimum distance between the nest holes is small. Trees have already been found that had no fewer than four nesting holes used by nasal cockatoos. The nests contain between two and four eggs. These are elliptical to elliptical-oval and dull. Both parent birds breed. The incubation period is 24 to 25 days. During the nestling season, both parent birds feed the nestlings. The young birds leave the nest cavity at around seven weeks. Experience in rearing nasal cockatoos indicates that the young birds will be fed by the female parent for some time afterwards.
Keeping in human care
Nose cockatoos are relatively seldom kept in human care. They are often considered to be less attractive cockatoos and are also extremely noisy birds. However, they become very affectionate and have a reputation for being good at imitating human language.
supporting documents
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 .
- PJ Higgins (Ed.): Handbook of Australian, New Zealand and Antarctic Birds. Volume 4: Parrots to Dollarbird. Oxford University Press, Melbourne 1999, ISBN 0-19-553071-3 .
- Dieter Hoppe : Cockatoos - way of life, keeping and breeding. Eugen Ulmer, Stuttgart 1986, ISBN 3-8001-7155-4 .
Individual evidence
- ↑ a b c d Forshaw, p. 222.
- ↑ a b c Hoppe, p. 165.
- ↑ a b Forshaw, p. 228.
- ↑ a b c Forshaw, p. 227.
- ↑ a b c Hoppe, p. 167.
- ↑ a b Forshaw, p. 225.
- ^ Forshaw, p. 226.
- ↑ Hoppe, p. 166.
- ↑ a b Forshaw, p. 230.
- ↑ a b Forshaw, p. 232.
- ^ Forshaw, p. 230 and p. 231.
Web links
- Cacatua tenuirostris inthe IUCN Red List of Threatened Species 2013.2. Listed by: BirdLife International, 2012. Retrieved December 26, 2013.