JOSEPH FORSHAW | Bird Talk Magazine
RESTRICTED TO NEW BRITAIN, the blue-eyed cockatoo (Cacatua ophthalmica) is one of the least-known cockatoos, both in the wild and in captivity.
Reported occurrences on neighboring New Ireland apparently refer to birds taken there from New Britain, where they are commonly kept or traded as pets and regularly offered for sale at markets in Rabaul.
Taking its name from the bright blue skin surrounding its eye, this species measures approximately 50 centimeters in length and superficially resembles the familiar sulphur-crested cockatoo (C. galerita), to which it is closely related.
The most prominent difference is in the crest. C. ophthalmica has a backward-curving crest of broad yellow feathers bordered by elongated white crown feathers. For further description of the distinguishing features, please refer to my Parrots of the World: An Identification Guide (Princeton University Press, 2006).
Our lack of information about the habits of these splendid cockatoos is due primarily to infrequent visits to New Britain by trained observers rather than to any scarcity of birds. In the 1960s, they were commonly found in rain forest throughout the lowlands and foothills up to about 1,000 meters, becoming rare and locally dispersed at higher altitudes.
Field surveys undertaken between December 1998 and April 1999 at two study sites along the east coast provided more precise estimates of abundance and a better understanding of habitat preferences.
At these study sites, observers encountered cockatoos only in forested areas, with counts of up to 73 birds per square kilometer in primary forest and selectively logged forest. The birds’ seemed to prefer those habitats over forest gardens or secondary forest, where counts were less than 28 birds per square kilometer.
Similar habitat preferences and levels of abundance were noted elsewhere on the island. A cautious extrapolation of population figures from the study sites was applied to New Britain as a whole, and this produced an estimate of 115,000 total birds.
Land clearance resulted in some habitat loss, so presumably those numbers have declined. Nevertheless, the absence of large-scale trapping and the preservation of extensive tracts of undisturbed forest keeps the species’ numbers high.
These cockatoos spend most of their time in the canopy and are usually seen singly, in pairs or small parties flying above the treetops. The discordant call-notes invariably betray their presence well before they come into view. A flock of 40 birds was the largest group encountered during the 1998-99 field surveys.
Corresponding to the birds’ main bouts of foraging, peak activity levels for the blue-eyed cockatoo take place in the early morning and late afternoon. During these times, the birds are seen in the vicinity of villages. At midday they shelter amidst the canopy foliage.
They gather in flocks of 10 to 20 around dusk in tall trees for their pre-roost gatherings, engaging in aerobatics accompanied by constant screeching. On one occasion, a cockatoo was seen flying down a steep mountain slope, descending nearly 1,000 feet before turning and twisting, as if to reduce speed, and then disappearing into a forested canyon.
Compared to the familiar screeching notes of sulphur-crested cockatoos, observers find these cockatoos’ calls more high-pitched, less raspy and more nasal. Recorded calls include a series of screams, each note terminating in a downward deflection, usually emitted while perched.
A loud, nasal “aaah” was recorded at intervals of one to three seconds during flight. The flight comprises fluttering wingbeats interspersed with gliding.
Seeds, nuts, fruits, berries and probably insects and their larvae make up the blue eyed’s diet. The bird procures these items in the treetops. Some individuals were observed in coconut palms feeding on both flowers and fruits. Feeding on Melanolepis fruits, wild figs and blossoms of Eucalyptus deglupta was also recorded.
Blue-eyed cockatoos nest in a hollow limb or hole, high off the ground in a forest tree. Ten of the 13 nests found during the 1998-99 survey were in trees in primary forest, and all nests were in large trees at heights between 13 and 50 meters. Hollow entrances measured between 18 and 52 centimeters in length and between 14 and 38 centimeters in width.
Papua New Guinea’s strict conservation legislation prohibits commercial exports of wildlife, which makes it unlikely that we’ll be able to augment the captive population elsewhere in the world with new lines from wild blue-eyed cockatoos.
Also, while numbers in captivity remain fairly low, the genetic pool for breeding remains restricted, so every effort must be made to maximize successful breeding to ensure that this most interesting cockatoo can be maintained in collections.
For me, the blue-eyed cockatoo is almost synonymous with Chester Zoo, in northern England where I first encountered these birds. That institution has been particularly successful in breeding the species.
The University of Natural Resources and Environment is located on the island of New Britian.
As part of an Ecology course they could do a bird survey focusing specifically on this bird species, thus increasing knowledge about this unique bird.
Posted by: Lucy Timmer | 29 July 2012 at 11:13 AM