Yellow-crested cockatoo
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Yellow- crested Cockatoo ( Cacatua galerita ) |
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| Cacatua galerita | ||||||||||
| ( Latham , 1790) |
The yellow- crested cockatoo ( Cacatua galerita ) is a parrot from the cockatoo family .
Occurrence
Yellow-crested cockatoos occur in the north, east and south-east of Australia and Tasmania as well as the Palau Islands, on some islands of the southern Moluccas and in Indonesia. The species was also naturalized in southwest Australia and New Zealand. Their main area of distribution is in the southeast of Australia. Yellow-crested cockatoos are very numerous there and can also be found very frequently in cities such as Sydney and Canberra . The yellow-crested cockatoo colonizes an extremely large distribution area even without taking into account the regions in which it was settled. It has a north-south extension of about 5,000 kilometers and an east-west extension of about 4,000 kilometers and includes landscape zones of temperate, subtropical and tropical climates. Only very few other parrot species have a comparable distribution area.
Yellow-crested cockatoos are appealing birds that are kept as aviary birds around the world.
Appearance
Yellow-crested cockatoos reach a body length of 50 centimeters. They weigh between 720 and 1020 grams. These are medium-sized cockatoos. Its broad, rounded wings and strong gray-black beak are striking. There is no gender dimorphism . Males tend to be slightly heavier. The eye color of the females is often a reddish brown, while the iris of the males is dark brown to almost black.
The basic color of the plumage is white. The hood feathers are yellow, narrow and curved forward. They are delimited from the forehead by elongated white forehead feathers. The ear-coverts as well as the base of the cheeks and the throat feathers are pale yellow. Both the inner flags of the flight feathers and the control feathers have a pale yellow tinge.
Yellow-crested cockatoos fly with fast and flat wing beats. The flight is repeatedly interrupted by short gliding phases. When alternating between the feeding ground and their sleeping trees, they move at a considerable height. They then slide down in sweeping circles to tree height and then settle in the treetops. They shout loudly during the flight. The contact call is a harsh, loud screech. Nestlings and young birds make panting feed-bed noises.
habitat
Yellow-crested cockatoos are adaptable birds that are found in a wide variety of vegetation regions. In semi-arid regions they prefer habitats along tree-lined watercourses. But they also occur in a variety of other tree-lined landscapes and also colonize tropical and subtropical rainforests, gallery forests , mangroves and hardy deciduous forests that are damp in winter . In contiguous forests, their population is low. However, they are usually numerous in forests with cleared areas and clearings. They are also found on pasture and farmland that is sparsely covered with eucalyptus , allocasuarina , and callitris trees. They have developed very well into urban habitats and are very common in the urban areas of Sydney and Canberra , for example . They use golf and sports fields as well as gardens and parks there. Open, treeless lowlands and pastures are avoided by this cockatoo species.
Their height distribution does not exceed the 1000 meter limit in the north. In New South Wales they can be found in the Southern Highlands up to an altitude of 1,300 meters above sea level. In the south they avoid regions with an altitude of more than 600 meters above sea level.
Mated yellow-crested cockatoos are based on current knowledge in a territory around their breeding tree. Young birds that are not yet sexually mature and a few non-breeding pairs, on the other hand, move around in an undirected nomadic manner and in doing so also develop new foraging grounds or suitable habitats. In the paired yellow-crested cockatoos, however, there are indications of a vertical migration. Yellow-crested cockatoos that breed at high altitudes move to lower altitudes. Such limited vertical migration has been documented for the Southern Highlands in New South Wales , among others , where few isolated pairs remain in the breeding area in winter and the majority of the population retreats to regions below 1,100 meters at the beginning of winter.
food
Yellow-crested cockatoos mostly find their food on the ground. It consists mainly of berries, nuts, seeds, roots and fruits as well as herbs, caterpillars, locust eggs, wood-dwelling insects and larvae. Yellow-crested cockatoos can cause considerable damage on agricultural land. Among other things, they dig up freshly sown or sprouting seeds and eat maturing crops. Similar to pink cockatoos, they also open sacks of grain. They plunder corn fields. They prefer to eat maize long before the ripening period, so that farmers cannot take preventive measures by harvesting ripe plants quickly. However, they also eat seeds from a number of plants that are considered agricultural weeds.
behavior
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Yellow-crested cockatoos are noisy and conspicuous birds. Outside of the breeding season, they form swarms that can consist of a few hundred specimens. Such flocks are very vigilant and have a warning system in which several cockatoos remain in the trees while the rest of the flock searches for food on the ground. If the “guards” feel alarmed, they fly up screeching loudly. The swarm eating on the ground joins this escape behavior. It is difficult to get close to yellow-crested cockatoos for this reason. Sometimes also join Galahs to these swarms. Pink cockatoos do not have such a guard system and benefit from the attention of the yellow-crested cockatoos. Outside of the breeding season, yellow-crested cockatoos stay mostly in pairs or in small family groups.
Yellow-crested cockatoos show a close bond with their sleeping trees. These are used over a long period of time, even if this means that they have to travel long distances to reach their feeding grounds. In the Iron Range National Park east of the Cape York Peninsula , a tree is known that has been used as a sleeping tree every year in November and December since 1990. Up to 500 yellow-crested cockatoos gather on this tree.
Yellow-crested cockatoos are diurnal birds. At sunrise they leave their sleeping trees with loud screams and then usually first go to a nearby water point. They then fly to the feeding places, from which they only return to their sleeping places at dusk. Your activity phase has two high points. Morning feeding is interrupted when the hottest time of the day arrives. They then seek shelter in the canopy of the adjacent trees, doze there and take care of their plumage. In the afternoon, they return to the ground to feed. As a rule, they go to another watering hole before settling down in their sleeping trees again.
Similar to pink cockatoos, yellow-crested cockatoos react with great excitement to downpours. They often hang upside down in the branches and get soaked with flapping wings and loud screeching. In strong winds, they also show playful acrobatics in which they let themselves be carried along by the gusts of wind.
Reproduction
Like most cockatoos, yellow-crested cockatoos have a very simple courtship repertoire. The males strut with their bonnets erect and their posture tense along a branch towards the female. They bow in the direction of the female. The breeding season is variable and depends on the climatic conditions of the respective distribution area. In the south of Australia it falls between August and January. In the north of the distribution area, Yellow-crested Cockatoos breed from May to September.
Yellow-crested cockatoos are cave breeders. They prefer to use eucalyptus as a breeding tree, which is as close to water as possible. In some regions, such as on the banks of the Murray River, yellow-crested cockatoos also breed in caves in steep walls. The clutch consists of two, less often three eggs. The nest underlay in the breeding caves are small pieces of wood and sludge. The incubation period is 27 days. Both sexes breed. The young are fully fledged at around ten weeks.
Systematics
As with many other parrot species, the number of subspecies is debatable. Here the division is followed as suggested by Joseph M. Forshaw .
| subspecies | Distribution area | Distinguishing features of the individual subspecies |
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| C. g. galerita , nominate form | The distribution area includes eastern and southeastern Australia. It extends from north Queensland to Tasmania and the southeast of South Australia | The nominate form is the largest subspecies. The featherless eye ring is white. |
| C. g. queenslandica | The distribution area is the Cape York Peninsula including the coastal islands in the southern Torres Strait | The subspecies is smaller than the nominate form. The beak is wider with a conspicuous ridge. |
| Mathews Yellow- crested Cockatoo ( C. g. Fitzroyi ) | Northern Australia from the Kimberley Division in Western Australia to the Fitzroy River and the north of the Northern Territory | In this subspecies, the eye ring is light blue. The beak is wider with a noticeable ridge. The featherless eye ring is bluish white. The proportion of yellow in the plumage is reduced compared to the nominate form |
Yellow-crested cockatoos and human
Yellow-crested cockatoos as pests
There are two feral populations in southwest Australia that emerged from captive refugees. The region is used intensively for agriculture and is therefore also known as the wheat belt . Yellow-crested cockatoos, like the pink cockatoos, are considered pests, as they can cause great damage on agricultural land. Yellow-crested cockatoos also compete here for nesting holes with the endemic and far rarer cockatoo species such as Carnaby's white-eared black cockatoo and Baudin's white-eared black cockatoo .
The population in southwest Australia ranges between three hundred and five hundred individuals. Australian authorities have released these populations for shooting and trapping. However, this measure has so far remained unsuccessful, so that it is feared that the yellow-crested cockatoo will continue to spread here.
In other regions of Australia the yellow-crested cockatoo is a protected species. However, farmers occasionally receive special permits to shoot and catch this species of cockatoo in order to limit damage to arable land. As with other parrot species, the damage can be significant. Ornithologists and conservationists point out, however, that farmers have to operate their cultivation areas to a greater extent, taking into account the local avifauna . The cultivation of oilseeds in regions with a high population density of yellow-crested cockatoos, for example, provokes such damage.
Keeping in human care
In general, you should think twice about purchasing yellow-crested cockatoos; because a natural and species-appropriate keeping is usually only rarely possible. Individual keeping is not appropriate to the species and is prohibited in Germany and Austria. Yellow-crested cockatoos also reach a considerable age. It has been proven that they can live for more than eighty years.
Yellow-crested cockatoos are very adaptable and require a lot of attention and sufficient space. Yellow-crested cockatoos are very adaptive, curious and can become very clingy due to their highly developed social and emotional life. Yellow-crested cockatoos are also very noisy birds. They screech very loud, especially in the early hours of the morning. They also have a high tendency to gnaw and can cause considerable damage in homes.
Housing in a large free-flight aviary with a heated room is considered species-appropriate. Commercially available cages with a volume of approx. 0.5 m³ are completely unsuitable for all larger cockatoo species, as they do not do justice to the animals' natural urge to move. Only an aviary is considered species-appropriate, in which the cockatoos can also fly unsupervised. The high need for gnawing should be taken into account by regularly getting deciduous branches.
Cockatoos are very susceptible to the psittacine beak and feather disease (PBFD; English for "feather and beak disease of parrots"). This is a highly contagious, incurable, and often fatal viral infection that occurs in parrot birds. It is the most common viral disease in parrots in Germany and now affects not only large parrots, but also budgies and other small parrot birds.
The causative agent of the PBFD is the Beak and Feather disease virus (BFDV) from the virus genus Circovirus . These are small, 12–21 nm large, non-enveloped DNA viruses . Circoviruses are very contagious. They have a high tenacity in the environment and are only safely inactivated by a few disinfectants (e.g. glutaraldehyde ) . The infection is done by oral uptake of the virus or an airborne droplet infection. Due to the high tenacity, indirect transmission through inanimate vectors (cage furniture, clothing, claw scissors, etc.) is also possible. The incubation period , i.e. the period from infection to actual disease, can stretch on for months or even years. Therefore, when buying animals, there is a very high risk of the disease being introduced into a bird house.
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 galerita in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 30 of 2008.
- Videos, photos and sound recordings of Cacatua galerita in the Internet Bird Collection
Individual evidence
- ↑ Hoppe, p. 145.
- ↑ a b Forshaw, p. 168.
- ↑ a b c Hoppe, p. 141.
- ↑ a b Forshaw, p. 176.
- ^ Forshaw, p. 172.
- ^ Forshaw, p. 171.
- ↑ a b c Forshaw, p. 175.
- ↑ a b c Forshaw, p. 174.
- ^ Forshaw, p. 177.
- ↑ Minimum requirements for keeping parrots (January 10, 1995) , Federal Ministry of Food, Agriculture and Consumer Protection of the Federal Republic of Germany
- ↑ 2nd Animal Husbandry Ordinance on the homepage of the Austrian Federal Chancellery
- ↑ Appendix 2: Minimum requirements for keeping birds of the 2nd Animal Husbandry Ordinance, homepage of the Austrian Federal Chancellery
- ^ Forshaw, p. 178.