Female Galah
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Psittaciformes |
| Family: | Cacatuidae |
Microglossinae
Calyptorhynchinae
Cacatuinae
| Cockatoos | ||||||||||
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Female Galah
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Microglossinae |
A cockatoo is any of the 21 bird species belonging to the family Cacatuidae. Along with the Psittacidae family (the true parrots) and the Nestoridae family, they make up the order Psittaciformes. The name cockatoo originated from the Malay name for these birds, kaka(k)tua (either from kaka "parrot" + tuwah, or "older sister" from kakak "sister" + tua, "old"). Placement of the cockatoos as a separate family is fairly undisputed, but it is not resolved whether or not other living lineages of parrots (such as the lories and lorikeets) are as distinct as they are. The family has an Australasian distribution, ranging from the Philippines and Indonesia to the Solomon Islands and Australia.
Cockatoos are, on average, larger than the average size of true parrots; however, the cockatiel, the smallest cockatoo, is a small bird, and some of the largest parrots including the Hyacinth Macaw (the longest parrot) and the flightless Kakapo (the heaviest parrot), are true parrots. Their plumage is generally less bright than that of the other parrots, being white or black with some colour in the crest and tail. Like other parrots they have strong bills and feet.
The diet of the cockatoos is composed of seeds, fruit, flowers and insects. Cockatoos generally feed in large flocks, particularly if they feed on the ground. Cockatoos are monogamous and breed in cavities in trees.
Cockatoos are popular birds in aviculture, although for some species this trade has threatened their survival. Other species are threatened by habitat loss and particularly the loss of nesting holes as large old trees are lost. Some species have adapted well to human changes and are in fact considered agricultural pests.
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Cockatoos have a much more restricted range than the true parrots, occurring naturally only in Australasia.[1] Eleven of the 21 species exist in the wild only in Australia, while seven species occur in the islands of Indonesia, New Guinea, the Philippines and the Solomon Islands. Three species occur in both New Guinea and Australia. Some species have widespread distributions, for example the Galah occurs over most of Australia, whereas other species have tiny distribution, confined to a small part of the continent, like the Long-billed Black Cockatoo of West Australia, or to a small island group, like the Tanimbar Cockatoo, which is restricted to the Tanimbar Islands of Indonesia. Some cockatoos have been introduced accidentally to other areas outside their natural range such as New Zealand and Palau.[2]
Cockatoos occupy a wide range of habitats. The most widespread species are open country specialists that feed on grass seeds.[1] Species may also occupy woodlands, rainforests, shrublands and even alpine forests. Several species have adapted well to human modified habitats, and are found in agricultural areas and even busy cities.[3]
The cockatoos are generally large to medium sized parrots, with one species, the Cockatiel, being quite smaller than the other species.[1] Cockatoos share many features with other parrots including the characteristic curved beak shape and a zygodactyl foot, with two forward toes and two backwards toes. They differ, however in a number of characteristics, including the often spectacular movable headcrest, the presence of a gall bladder and some other anatomical details, and their lack of the Dyck texture feather composition which causes the bright blues and greens seen in true parrots.
Like other parrots, they have short tarsi but strong claws, and walk with a slow waddle, often using their strong bill as a third limb when climbing branches. They generally have long narrow wings used in rapid flight, with speeds of 70 km/h being recorded for some species. The black cockatoos, however, along with the Major Mitchell's Cockatoo, have shorted more rounded wings and a more leisurely flight.
The cockatoos have large bills which are kept sharp by rasping the two mandibles together when resting. The huge bills are complemented by large muscular tongues which help manipulate seeds inside the bills so that they can be de-husked before eating.[1] During the de-husking the lower mandible applies the pressure, the tongue holds the seed in place and the upper mandible acts as an anvil.
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, and usually on the crest or tail. A few species, like the Galah, have larger areas of colour. In addition to their plumage many species have brightly coloured bare areas around the eye and face, with the Palm Cockatoo having a large red patch of bare skin across the face. A few species exhibit sexual dimorphism in the plumage, with this being most pronounced in the Gang-gang Cockatoo and the Cockateil. Sexual differences in plumage are more common in the black cockatoos, but many cockatoos vary slightly in overall size and weight, with the males being on average larger. The iris colour is often brown in adult females and differs from the black irises often seen in adult males, but this may not be totally reliable to identify the gender of a cockatoo.
Cockatoos are diurnal, requiring daylight to find their food.[1] They are not early risers, instead waiting until the sun has warmed their roosting sites before feeding. The 21 species are generally highly social and will roost, forage and travel together, often in large flocks. All species require roosting sites that are sometimes located near drinking sites, but many species may travel great distances between the roosting sites and feeding sites.[4]
Cockatoos have several characteristic methods of bathing; they may hang upside down or fly about in the rain, or flutter in wet leaves in the canopy.[5]
The vocalisations of cockatoos are loud and harsh.[1] They serve a number of functions, including allowing individuals to recognise one another, warning others of predators, indicating individual moods, maintaining the cohesion of a flock and as warnings when defending nests. The use of calls and number of specific calls varies by species, some like the Short-billed Black Cockatoo have as many as 15 different calls, whereas others like the Major Mitchell's Cockatoo have far fewer. Some species, like the Gang-gang Cockatoo are comparatively quiet, but do have softer growling calls when feeding. In addition to vocalisations, the Palm Cockatoos communicate over large distances by drumming a dead branch with a stick.[6] Cockatoo species also make a characteristic hissing sound when threatened.[5]
The cockatoos are versatile feeders and consume a range of food items.[1] Seeds form a large part of the diet of all species; these are opened with their large and powerful bills. Cockatoos may feed either individually or in flocks that range in size from small to quite immense. The Galahs, corellas and some of the black cockatoos fee primarily on the ground, others feed mostly in trees. The ground feeding species tend to feed in flocks, which can wither feed in tight, squabbling groups where seeds are concentrated, or in more dispersed lines where the seeds are less concentrated and more widely distributed.
While some cockatoos are generalists taking a wide range of seeds, others are specialists. The Glossy Black Cockatoo specialises in the cones of Allocasuarina, often a single species, which it holds in its food and shreds with its powerful bill before removing the seeds with its tongue.[7] Some species take large numbers of insects, particularly when breeding. The large bill is used in order to extract grubs and larvae from rotting wood. The amount of time cockatoos have to spend foraging varies with the season. During times of plenty, they may only need to feed for a few hours in the day, in the morning and evening, and spend the rest of the day loafing, but during the winter most of the day may be spent foraging. During hard times the cockatoos also display versatility in their diet, travelling widely in order to find food, feeding on more green plant material and in some species using their large bills to dig up corms.
Cockatoos are monogamous breeders, with pair bonds that can last many years. They may also display site fidelity, returning to the same nesting sites in consecutive years.[6] Courtship is generally simple, particularly for established pairs, with the black cockatoos alone engaging in courtship feeding. Established pairs do engage in allopreening, but all forms of courtship drop off after incubation begins, possibly due to the strength of the pair-bond.[8]
Like most parrots the cockatoos are cavity nesters, nesting in holes in trees.[9] In many places these holes are scarce and the source of competition, both with other members of the same species and with other species and types of animal.[10] This competition is particularly intense amongst larger species.
The nesting hollows are lined with sticks, wood chips and branches with leaves. The eggs of cockatoos are oval and initially white, although they become discoloured over the course of incubation. They range in size from 55*40 mm in the Palm Cockatoo to 26*18 mm in the Cockateil. Clutch size varies amongst the family, with the Palm Cockatoo and some other larger cockatoos laying only a single egg, and the smaller species laying anywhere between two to eight eggs. Amongst the cockatoos incubation and brooding responsibilities may either be undertaken by the female alone in the case of the black cockatoos or shared amongst the sexes as happens in the other species. In the case of the black cockatoos the female is provisioned by the male several times a day.
A 1999 genetic study by Brown and Toft reviewed the existing evidence and additional mitochondrial 12S rRNA sequence data to arrive at a well-supported phylogeny of the cockatoos.[11] They could distinguish 3 subfamilies:
The genera Calyptorhynchus and Cacatua can be further subdivided into two subgenera each, and in the latter case as a distinct third lineage the white-and-pink Major Mitchell's Cockatoo, which is intermediate in coloration between the grey-and-pink Galah and the white Cacatua. Some argue that it is best recognized as a monotypic genus Lophochroa as has been suggested by Brown & Toft (1999).[11]
A single study using Intron 7 of nuclear β-fibrinogen sequence data suggests that the Microglossinae may have diverged later, and that the cockatiel might be distinct enough to warrant recognition of the Nymphicinae.[12]. However, a recent much more extensive study[13] using 5 different gene sequences confirmed the study of Brown & Toft (1999) as did the study by Tokita el at (2007)[14] and Adams et al. (1984)[15]
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, was found in Early Miocene (16-23 million years ago) deposits of Riversleigh, Australia.[16] In Melanesia, subfossil bones of Cacatua species which apparently did not survive early human settlement were found on New Caledonia and New Ireland.[17] [18] The bearing of these fossils on cockatoo evolution and phylogeny is fairly limited, except that the Riversleigh fossil allows some tentative dating of the divergence of subfamilies.
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Cockatoos are very popular as pets, not only for their appearance but also for their intelligence and engaging personalities.[1] Well-socialised cockatoos are often affectionate not only to their owner but to strangers as well. In spite of their attractiveness as pets there are drawbacks; they are potentially destructive, with the larger cockatoos in particular prone to destructive behaviour. Cockatoos may show aggression during the breeding season; cockatoos are capable of very strong and painful bites. They also require attention, although experts warn against "spoiling" young birds with too much attention as it make make the bird dependent on the owner, leading to problems later in life. Another drawback as a pet is the fact that most cockatoo species are very loud birds, though they naturally only vocalize for short periods of time twice a day. They can be expensive pets, with a cost which typically ranges from $500-$2000 for the more commonly available species. In addition to the actual cost, cockatoos require a very large cage for their size. Cockatoos also require an out of cage gym or perch and a steady supply of toys, branches, cardboard boxes, or other chewable items, which prevents future self destructive behaviour such as feather plucking. Cockatoos are capable of living up to 30-70 years depending upon species (around 20 years fro the smaller Cockateils) and as such they require a long term commitment from their owners. Their longevity is also considered a positive trait as it reduces instances of the loss of a pet.[1]
Cockatoos are popular for use in trained bird shows, and they can also be trained as pets. Cockatoos are generally less food motivated than other birds; some birds may be more motivated by a reward of petting or praise than of food. Cockatoos can often be trained to accept a parrot harness, enabling their owners to take them outdoors. Cockatoos have been used in animal-assisted therapy, generally in nursing homes.
In general, the smaller cockatoo species such as Galahs and Goffin's Cockatoos are considered to be much easier to keep as pets than large cockatoos such as Moluccans. In Australia, where Galah cockatoos are extremely abundant and inexpensive, they are often considered to be good first birds. The smallest species of cockatoo, the Cockatiel is a non-destructive and less demanding alternative making them extremely popular as pets, and among the species most often recommended to new bird owners.
Cockatoos often have pronounced responses to musical sounds, and numerous videos exist showing the birds "dancing" to popular music. Research conducted in 2008 with an Eleonora Cockatoo named Snowball had indicated that this particular individual is indeed capable of perceiving music and synchronizing its body movements to the beat - i.e. dancing.[19]
The Palm Cockatoo, which has a unique beak and face colouration, is used as a symbol by the World Parrot Trust.
In Australian slang or vernacular speech a person who is deputed to keep a look-out whilst colleagues undertake clandestine or illegal activities particularly such as organising illegal gambling may be referred to as a "cockatoo".[1] Proprietors of small agricultural undertakings are frequently jocularly or slightly disparagingly referred to as a "cocky".[20]
 An apparent Sulphur-crested Cockatoo in a painting by Andrea Mantegna, 1496 - over a hundred years before the first recorded European sighting of the Australian continent. |
 Two Sulphur-crested Cockatoos in a painting by Melchior de Hondecoeter, second half of 17th century |
Human activities have had positive effects on some species of cockatoo and negative effects on others. According to the IUCN and BirdLife International seven species of cockatoo are considered to be vulnerable or worse, and a further species is considered to be near threatened.[21] Of these two, the Philippine Cockatoo and the Yellow-crested Cockatoo, are considered to be critically endangered.
The principal threats to cockatoos are habitat loss and the wildlife trade. All cockatoos are dependent on trees for nesting and are vulnerable to their loss, in addition many species have specialised habitat requirements or live on small islands and have naturally small ranges already, making them vulnerable to the loss of these habitats.[22] Cockatoos are popular as pets, and the capture and trade has threatened some species. For example between 1983 and 1990, 66,654 Moluccan Cockatoos were exported from Indonesia, a figure that does not include the number of birds caught for the domestic trade or that were exported illegally.[23] The capture of many species has subsequently been banned, but the trade continues illegally.
All species of cockatoo are protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (also known as CITES), which makes the import, export and trade in all wild-caught parrots and cockatoos illegal.
The following cockatoo species are protected on the CITES appendix 1 list of endangered species.
All of the other cockatoo species are protected on the CITES appendix 2 list of vulnerable species. Some species of Australian cockatoos including corellas and galahs, have large populations and will raid orchards, vineyards and arable lands. They are considered to be serious pests of cereal crops in Australia.[24] These are sometimes killed as pests, but other mitigation methods are used as well including scaring, habitat manipulation and providing decoy foods to be consumed instead. Urban cockatoos can also be a nuisance due to destruction of property; cockatoos will maintain their bills by gnawing on sticks in the wild, in cities they may instead gnaw outdoor furniture, windows or solar water heaters.[3]
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