Palm Cockatoos (Probosciger aterrimus)

Abstract

The Genus Probosciger

T his monotypic genus contains the largest and probably the most spectacular of the cockatoos. The main diagnostic features of the genus include the huge, sharply pointed, upper mandible, the bare, red cheek-patches, and the naked inner thighs. A peculiarity of the beak is that the upper and lower mandibles do not close completely together, leaving the black-tipped, red tongue clearly visible. Another unique feature is the ahility of the hire! to

 

change the color of its naked cheek patches from red to pink and vice versa, depending on its mood. Excitement or alarm causes the patch to visibly deepen in color, a process known as "blushing."

Due to its blackish color Probosciger was formerly loosely classified along with the black cockatoos of the genus Calyptorbyncbus. Studies have revealed, however, that Probosciger has distinctive anatomical peculiarities which clearly separate it from the black cockatoos. The superficiality of any resemblance can quick-

 

ly be ascertained by comparing the size of the birds, examining the beak, and checking the colors and patterns of the plumage. Apart from the hare red cheek patches which do not occur in any of the black cockatoos, the plumage of Probosciger is almost totally and uniformly black in both sexes. Conversely, in Calyptorbyncbus, colorful and dominant hands are located on the tail, and there is quite marked plumage dimorphism of the sexes in most of the six species.

The relative enormity of

Probosciger to other cockatoo species and the size of its beak led early researchers to compare them with macaws. Even Kuhl, who named the genus, was compelled to write "Species intermedia inter Ara et Kakadoes" (species intermediate between macaws and cockatoos).

On comparing the hone structures of Probosciger and other cockatoos species, the great Australian ornithologist, Gregory M. Mathews,

 

wrote that "The osteology differs so much from that of other cockatoos that I have separated the present species as of family rank, and it is possible that a closer examination would cause it to be placed nearer the Macaws than the Cockatoos. It is obviously a very isolated form, however it is viewed, and worthy of extended investigation." (Mathews, 1916).

The specialized beak is unique among the cockatoos both for its size and its apparent function. The sharply pointed tip of the upper mandible extends well below the lower mandible, making it the largest beak of any psittacine in relation to its body size (only in the Hyacinthine Macaw, Anodorhynchus hyacinthinus, a larger bird, is the beak consistently more massive). The makeup of the upper mandible is interesting in that there are two projecting areas of flat horny tissue (rampotheca), which forms three steps. The inner step is used to deal with food items such as small seeds, while the middle step deals with the larger items. The tip of the beak, and the outermost step are used for tearing open large fruits. Holyoak 0972) concluded that, without these specialized steps, the bird would have great difficulty in dealing with small seeds.

The crest is also quite distinct from that of other cockatoo genera. It consists of numerous backward-curving, narrow feathers which separate when the crest is raised. The elongated feathers give the crest of the Palm Cockatoo a distinctive, plume-like quality unique among the cockatoos.

The Palm Cockatoo Probosciger aterrimus (Gmelin)

Synonyms: Great Palm Cockatoo, Great Black Cockatoo, Cape York Cockatoo, Black Macaw, Goliath Cockatoo, Aratoo.

Three subspecies are now generally recognized:

1. Prohosciger aterrimus aterrimus (Gmelin)

2. Prohosciger aterrimus goliath (Kuhl)

 

3. Probosciger aterrimus stenolopbus (Van Oort)

Native Range: Coastal and inner lowland areas of New Guinea to an altitude of some 1,300 m. but generally below 750 m. Also on islands in Geelvink Bay, the Aru Islands, and the West Papuan Islands. The northern tip of Cape York Peninsula, Queensland, Australia, south to Princess Charlotte Bay in the east, and the Archer River in the west. Formerly, introduced to Kai Cecil (east of Aru Archipelago) and still present in 1981.

Conservation Status: The Papua New Guinea and Indonesian populations of these birds are under threat from illegal trade, habitat loss, and human predation. The Australian population is under stricter protection. Wild populations of all three subspecies are estimated to be slightly in excess of 30,000 individuals. The species is listed under Appendix I in CITES.

 

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References

Diamond, Jared M. Avifauna of the Eastern Highlands of New Guinea. Nuttall Ornithological Cluh, Cambridge, 1972.

Forshaw, Joseph M. Some field observations on the Great Palm Cockatoo. Emu, Vol. 64, 1964, pp. 327-331.

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Holyoak, D. T Adaptive significance of bill shape in the Palm Cockatoo. Aviculture Magazine, Vol, 78, 1972, pp. 99 - 100.

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Aviary. Angus & Robertson,

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Tavistock, Marquess of. The display of the Palm Cockatoo. Aviculture Magazine, ser. 4, Vol. 6, 1928, p. 291.

Tavistock, Marquess of. Breeding notes for 1933.

Aviculture Magazine, 4th ser., Vol. II, 1933, pp. 319 - 387 . .,.,...