Probosciger aterrimus (Gmelin, 1788)

Size and Weight

The palm cockatoo, scientifically named Probosciger aterrimus, is 55 to 60 cm (22 to 24 in) long and weighs 910–1,200 g (2.01–2.65 lb). It may be the largest cockatoo species and largest parrot in Australia, though large races of yellow-tailed black cockatoos and sulphur-crested cockatoos broadly overlap in its size range.

Crest and Bill Structure

It is a distinctive bird with a large crest and one of the largest bills of any parrot; only the hyacinth macaw has a larger bill.

Bill Function

This powerful bill allows palm cockatoos to eat very hard nuts and seeds, and also lets males break off thick sticks, approximately 2.5 cm (1 inch) thick, from live trees to use for drumming displays. Males have larger beaks than females.

Unique Bill Morphology

The beak is unusual: for much of its length, the lower and upper mandibles do not meet, which lets the tongue hold a nut against the top mandible while the lower mandible cracks it open.

Coloration

The palm cockatoo also has a distinctive red cheek patch that changes colour when the bird is alarmed or excited.

Subspecies Differences

The subspecies P. a. goliath and P. a. stenolophus are larger than the nominate subspecies, and P. a. stenolophus also has narrower crest feathers.

Habitat Range

Palm cockatoos live in rainforests and woodlands of New Guinea and Cape York Peninsula, Queensland, Australia. They can still be found near Sorong, West Papua, Indonesia, where they are sometimes seen in trees along roads.

Territorial Drumming Display

Palm cockatoos have a unique territorial display: typically the male drums with a large stick or seed pod (up to 2.5 cm in diameter and 15 cm long) against a dead bough or tree, producing a loud noise that can be heard up to 100 m away. After drumming, the male occasionally strips the drumming tool into small pieces to line the nest.

Drumming Research Context

Although this drumming behaviour was discovered over three decades ago, in 1984 by G.A. Wood, the reason palm cockatoos drum is still not understood.

Drumming Hypotheses

One hypothesis is that females can assess the durability of the nesting hollow from the resonance of the drumming. Another possibility is that males drum to mark their territory against other males.

Tool Use Trait

The palm cockatoo is an unusual ancient species, and one of the few bird species known to use tools.

Feeding Timing

Palm cockatoos usually feed during the early hours of the day.

Diet Composition

Their diet consists mostly of wild pandanus palm fruits and kanari tree nuts. They have also been observed eating fruits of Darwin stringy bark and the nonda tree, as well as seeds from the cocky apple tree, beach almond, and black bean tree.