Cacatua dal ciuffo giallo

Identificazione

Sulphur-crested cockatoos are 44–55 cm (17.5–21.5 in) long, with the Australian subspecies larger than subspecies from New Guinea and nearby islands. The plumage is overall white, while the underwing and -tail are tinged yellow. The expressive crest is yellow. The bill is black, the legs are grey, and the eye-ring is whitish. Males typically have almost black eyes, whereas the females have a more red or brown eye, but this requires optimum viewing conditions to be seen. The differences between the subspecies are subtle. C. g. fitzroyi is similar to the nominate race but lacks the yellow on the ear tufts and has slightly blueish skin around the eye. C. g. eleonora is similar to C. g. fitzroyi but is smaller and has broader feathers in the crest, and C. g. triton is similar to C. g. eleonora except it has a smaller bill.<p>It is similar in appearance to the three species of corellas found in Australia. However, corellas are smaller, lack the prominent yellow crest and have pale bills. In captivity, the sulphur-crested cockatoo is easily confused with the smaller yellow-crested cockatoo or the blue-eyed cockatoo with a differently shaped crest and a darker blue eye-ring.

Tassonomia

Nome scientifico

Cacatua galerita

Autorità

(Latham, 1790)

Ordine

Psittaciformi

Famiglia

Cacatuidi

Genere

Cacatua

Areale e habitat

In Australia, sulphur-crested cockatoos can be found widely in the north and east, ranging from the Kimberley to as far south as Tasmania, but avoiding arid inland areas with few trees. They are numerous in suburban habitats in cities such as Adelaide, Melbourne, Canberra, Sydney, Brisbane and Perth. Except for highland areas, they occur throughout most of New Guinea and on nearby smaller islands such as Waigeo, Misool and Aru, and various islands in the Cenderawasih Bay and Milne Bay.There are four recognised subspecies:<p>Within Australia, sulphur-crested cockatoos of the nominate race have also been introduced to Perth, which is far outside the natural range. Outside Australia, they have been introduced to Singapore, where their numbers have been estimated to be between 500 and 2000. They have also been introduced to Palau and New Zealand. In New Zealand, the introduced populations may number less than 1000. This species has also been recorded as established in Hawaii and from various islands in Wallacea (e.g. Kai Islands and Ambon), but it is unclear if it has managed to become established there.

Migrazione

Resident species

Comportamento

Sulphur-crested cockatoos' distinctive raucous calls can be very loud, which is a result of an adaptation in order to travel through the forest environments in which they live, including tropical and subtropical rainforests. These birds are naturally curious, as well as very intelligent. They have adapted very well to European settlement in Australia and live in many urban areas.<p>Being intelligent, in Sydney, Australia, they have learned how to open garbage bins as a source of food. The behavior spreads among the birds by imitation. In captivity some will spontaneously dance to music with a variety of unique moves.<p>These birds are very long-lived, and can live upwards of 70 years in captivity, although they only live to about 20–40 years in the wild. They have been known to engage in geophagy, the process of eating clay to detoxify their food. These birds produce a very fine powder to waterproof themselves instead of oil as many other birds do.<p>The sulphur-crested cockatoo is a seasonal breeder in Australia; little is known about its breeding behaviour in New Guinea. In southern Australia, the breeding season is from August to January, whereas in northern Australia the season is from May to September. The nest is a bed of wood chips in a hollow in a tree. Like many other parrots it competes with others of its species and with other species for nesting sites. Two to three eggs are laid and incubation lasts between 25–27 days. Both parents incubate the eggs and raise the nestlings. The nestling period is between 9 and 12 weeks, and the young fledglings remain with their parents for a number of months after fledging.<p>Sulphur-crested cockatoos have a range of visually observable expressions. A 2009 study involving an Eleonora cockatoo (the subspecies Cacatua galerita eleonora) named Snowball found that sulphur-crested cockatoos are capable of synchronizing movements to a musical beat. Sulphur-crested cockatoos use facial expressions (with their feathers) to indicate positive emotions.<p>Species that feed on the ground are very vulnerable to predator attack. The cockatoo has evolved a behavioural adaptation to protect against this: whenever there is a flock on the ground, there is at least one high up in a tree (usually a dead tree), keeping guard. This is so well known that it has even entered Australian slang: a person keeping guard for sudden police raids on illegal gambling gatherings is referred to as a cockatoo or cocky for short.

Conservazione

Tendenza della popolazione

declining