Cockatoo


A cockatoo is any of the 21 species of parrots belonging to the family Cacatuidae, the only family in the superfamily Cacatuoidea. Along with the Psittacoidea and the Strigopoidea, they make up the order Psittaciformes. The family has a mainly Australasian distribution, ranging from the Philippines and the eastern Indonesian islands of Wallacea to New Guinea, the Solomon Islands and Australia.
Cockatoos are recognisable by their prominent crests and curved bills. Their plumage is generally less colourful than that of other parrots, being mainly white, grey, or black and often with coloured features in the crest, cheeks, or tail. On average, they are larger than other parrots; however, the cockatiel, the smallest cockatoo species, is medium-sized. The phylogenetic position of the cockatiel remains unresolved, except that it is one of the earliest offshoots of the cockatoo lineage. The remaining species are in two main clades. The five large black-coloured cockatoos of the genus Calyptorhynchus form one branch. The second and larger branch is formed by the genus Cacatua, comprising 12 species of white-plumaged cockatoos and three monotypic genera that branched off earlier, namely the pink and grey galah, the mainly grey gang-gang cockatoo and the large black-plumaged palm cockatoo.
Cockatoos prefer to eat seeds, tubers, corms, fruit, flowers, and insects. They often feed in large flocks, particularly when ground-feeding. Cockatoos are monogamous and nest in tree hollows. Some cockatoo species have been adversely affected by habitat loss, particularly from a shortage of suitable nesting hollows after large, mature trees are cleared; conversely, some species have adapted well to human changes and are considered agricultural pests.
Cockatoos are popular birds in aviculture, but their needs are difficult to meet. The cockatiel is the easiest cockatoo species to maintain and is by far the most frequently kept in captivity. White cockatoos are more commonly found in captivity than black cockatoos. Illegal trade in wild-caught birds contributes to the decline of some cockatoo species in the wild.

Etymology

The word cockatoo dates from the 17th century and is derived from Dutch kaketoe, which in turn is from the Indonesian/Malay kakatua. Seventeenth-century variants include cacato, cockatoon and crockadore, and cokato, cocatore and were used in the 18th century. The derivation has also been used for the family and generic names Cacatuidae and Cacatua, respectively.
In Australian slang or vernacular speech, a person who is assigned to keep watch while others undertake clandestine or illegal activities, particularly gambling, may be referred to as a "cockatoo". Proprietors of small agricultural undertakings are often jocularly or slightly disparagingly referred to as "cocky farmers".

Taxonomy



The cockatoos were first defined as a subfamily Cacatuinae within the parrot family Psittacidae by English naturalist George Robert Gray in 1840, with Cacatua the first listed and type genus. This group has alternately been considered as either a full or subfamily by different authorities. American ornithologist James Lee Peters in his 1937 Check-list of Birds of the World and Sibley and Monroe in 1990 maintained it as a subfamily, while parrot expert Joseph Forshaw classified it as a family in 1973. Subsequent molecular studies indicate that the earliest offshoot from the original parrot ancestors were the New Zealand parrots of the family Strigopidae, and following this the cockatoos, now a well-defined group or clade, split off from the remaining parrots, which then radiated across the Southern Hemisphere and diversified into the many species of parrots, parakeets, macaws, lories, lorikeets, lovebirds and other true parrots of the superfamily Psittacoidea.
The relationships among various cockatoo genera are largely resolved, although the placement of the cockatiel at the base of the cockatoos remains uncertain. The cockatiel is alternatively placed basal to all other cockatoo species, as the sister taxon to the black cockatoo species of the genus Calyptorhynchus or as the sister taxon to a clade consisting of the white and pink cockatoo genera as well as the palm cockatoo. The remaining species are within two main clades, one consisting of the black species of the genus Calyptorhynchus while the other contains the remaining species. According to most authorities, the second clade includes the black palm cockatoo, the grey and reddish galah, and the gang-gang cockatoo, although Probosciger is sometimes placed basal to all other species. The remaining species are mainly white or slightly pinkish and all belong to the genus Cacatua. The genera Eolophus and Cacatua are hypomelanistic. The genus Cacatua is further subdivided into the subgenera Licmetis, commonly known as corellas, and Cacatua, referred to as white cockatoos. Confusingly, the term "white cockatoo" has also been applied to the whole genus. The five cockatoo species of the genus Calyptorhynchus are commonly known as black cockatoos, and are divided into two subgenera—Calyptorhynchus and Zanda. The former group are sexually dichromatic, with the females having prominently barred plumage. The two are also distinguished by differences in the food-begging calls of juveniles.
The fossil record of cockatoos is even more limited than that of parrots in general, with only one truly ancient cockatoo fossil known: a species of Cacatua, most probably subgenus Licmetis, found in Early Miocene deposits of Riversleigh, Australia. Although fragmentary, the remains are similar to the western corella and the galah. In Melanesia, subfossil bones of Cacatua species which apparently did not survive early human settlement have been found on New Caledonia and New Ireland. The bearing of these fossils on cockatoo evolution and phylogeny is fairly limited, although the Riversleigh fossil does allow tentative dating of the divergence of subfamilies.

Genera and species

There are about 44 different birds in the cockatoo family Cacatuidae including recognized subspecies. The current subdivision of this family is as follows:
Subfamily Nymphicinae
  • Genus Nymphicus
  • *Cockatiel, Nymphicus hollandicus
Subfamily Calyptorhynchinae: Black cockatoos
  • Genus Calyptorhynchus – black-and-red cockatoos
  • *Red-tailed black cockatoo, Calyptorhynchus banksii
  • *Glossy black cockatoo, Calyptorhynchus lathami
  • Genus Zanda – black-and-yellow/white cockatoos
  • *Yellow-tailed black cockatoo, Zanda funerea
  • *Carnaby's black cockatoo, Zanda latirostris
  • *Baudin's black cockatoo, Zanda baudinii
Subfamily Cacatuinae
  • Tribe Microglossini: One genus with one species, the black palm cockatoo.
  • * Genus Probosciger
  • **Palm cockatoo, Probosciger aterrimus
  • Tribe Cacatuini: Four genera of white, pink and grey species.
  • * Genus Callocephalon
  • **Gang-gang cockatoo, Callocephalon fimbriatum
  • * Genus Eolophus
  • **Galah, Eolophus roseicapilla
  • * Genus Cacatua
  • ** Subgenus Cacatua – true white cockatoos
  • ***Yellow-crested cockatoo or lesser sulphur-crested cockatoo, Cacatua sulphurea
  • ***Citron-crested cockatoo, Cacatua citrinocristata
  • ***Sulphur-crested cockatoo, Cacatua galerita
  • ***Blue-eyed cockatoo, Cacatua ophthalmica Sclater, 1864
  • ***White cockatoo or umbrella cockatoo, Cacatua alba
  • ***Salmon-crested cockatoo or Moluccan cockatoo, Cacatua moluccensis
  • ** Subgenus Licmetis – corellas
  • ***Long-billed corella, Cacatua tenuirostris
  • ***Western corella, Cacatua pastinator
  • ***Little corella, Cacatua sanguinea Gould, 1843
  • ***Tanimbar corella or Goffin's cockatoo, Cacatua goffiniana Roselaar and Michels, 2004
  • ***Solomons cockatoo or Ducorps's cockatoo, Cacatua ducorpsii Pucheran, 1853
  • ***Red-vented cockatoo or Philippine cockatoo, Cacatua haematuropygia
  • **Subgenus Lophochroa – pink cockatoos
  • ***Pink cockatoo or Major Mitchell's/Leadbeater's cockatoo, ''Cacatua leadbeateri''

    Morphology

The cockatoos are generally medium to large parrots of stocky build, which range from in length and in weight; however, one species, the cockatiel, is considerably smaller and slimmer than the other species, being long and in weight. The movable headcrest, which is present in all cockatoos, is spectacular in many species; it is raised when the bird lands from flying or when it is aroused. Cockatoos share many features with other parrots, including the characteristic curved beak shape and a zygodactyl foot, with the two middle toes forward and the two outer toes backward. They differ in the presence of an erectile crest and their lack of the Dyck texture feather composition which causes the bright blues and greens seen in true parrots.
Like other parrots, cockatoos have short legs, strong claws, a waddling gait and often use their strong bill as a third limb when climbing through branches. They generally have long broad wings used in rapid flight, with speeds up to being recorded for galahs. The members of the genus Calyptorhynchus and larger white cockatoos, such as the sulphur-crested cockatoo and the pink cockatoo, have shorter, rounder wings and a more leisurely flight.
File:Callocephalon fimbriatum -NSW -Australia-8.jpg|thumb|left|A pair of gang-gang cockatoos in NSW, Australia. Cockatoos make lasting pair bonds.|alt=Two grey cockatoos on a lichen-covered tree branch. The red crested male is on the left.
Cockatoos have a large bill, which is kept sharp by rasping the two jaws together when resting. The bill is complemented by a large muscular tongue which helps manipulate seeds inside the bill so that they can be de-husked before eating. During the de-husking, the lower jaw applies the pressure, the tongue holds the seed in place and the upper jaw acts as an anvil. The eye region of the skull is reinforced to support muscles which move the jaws sideways. The bills of male cockatoos are generally slightly larger than those of their female counterparts, but this size difference is quite marked in the palm cockatoo.
The plumage of the cockatoos is less brightly coloured than that of the other parrots, with species generally being either black, grey or white. Many species have smaller areas of colour on their plumage, often yellow, pink and red, usually on the crest or tail. The galah and Major Mitchell's cockatoo are more broadly coloured in pink tones. Several species have a brightly coloured bare area around the eye and face known as a periophthalmic ring; the large red patch of bare skin of the palm cockatoo is the most extensive and covers some of the face, while it is more restricted in some other species of white cockatoo, notably the corellas and blue-eyed cockatoo. The plumage of males and females is similar in most species. The plumage of the female cockatiel is duller than the male, but the most marked sexual dimorphism occurs in the gang-gang cockatoo and the two species of black cockatoos in the subgenus Calyptorhynchus, namely the red-tailed and glossy black cockatoos. The iris colour differs in a few species, being pink or red in the female galah and the pink cockatoo and red-brown in some other female white cockatoo species. The males all have dark brown irises.
File:Fuß eines Weißhaubenkakadus.JPG|upright|right|thumb|A white cockatoo's left foot clasping aviary bars showing claws, scaly skin and zygodactyly—the middle two toes forward and the outer two toes backward.|alt=Closeup of a cockatoo's left foot grasping the wires of a cage. The foot is covered with grey-scaly skin and has four toes each with a dark grey curved claw
Cockatoos maintain their plumage with frequent preening throughout the day. They remove dirt and oil and realign feather barbs by nibbling their feathers. They also preen other birds' feathers that are otherwise hard to get at. Cockatoos produce preen-oil from a gland on their lower back and apply it by wiping their plumage with their heads or already oiled feathers. Powder-down is produced by specialised feathers in the lumbar region and distributed by the preening cockatoo all over the plumage.
Moulting is very slow and complex. Black cockatoos appear to replace their flight feathers one at a time, their moult taking two years to complete. This process is much shorter in other species, such as the galah and long-billed corella, which each take around six months to replace all their flight feathers.