Birds
Palm Cockatoo
Probosciger aterrimus · also called goliath cockatoo, great black cockatoo
In the rainforests of Cape York and New Guinea, a large black cockatoo does something no other bird is known to do: it makes a drumstick. A male palm cockatoo breaks off a branch, trims it to size, grips it in one foot, and beats out a rhythm against a hollow tree — a personal beat he keeps for years, advertising his claim on a rare nest hollow.
Overview
Probosciger aterrimus is a big smoky-black parrot, 50 to 65 cm long, with a tall crest, a bare red cheek patch on each side of the face, and the largest bill of any parrot relative to its head. It lives in rainforest and monsoon forest and nearby savanna woodland across New Guinea, the Aru Islands, and the northern tip of Australia, feeding on very hard nuts and seeds.
The drumming display
The palm cockatoo is one of very few animals known to craft a tool to make sound. A displaying male shapes a stick or seed pod and drums it against a hollow trunk beside a potential nest, and long-term study on Cape York has found that each male keeps his own rhythm and style over the years. The red cheeks flush brighter when the bird is excited and fade when it is calm, giving a live readout of its mood.
A slow breeder
Palm cockatoos are among the slowest-breeding parrots, raising on average well under one chick every two years, from a single egg laid on a bed of splintered sticks in a deep tree hollow. They are also very long-lived, commonly 40 to 60 years. That combination — few young, long life, dependence on big old trees — makes lost populations very slow to rebuild.
Status
The palm cockatoo is listed as Near Threatened and declining. It remains fairly widespread in New Guinea but is falling there through logging, while the separate Cape York population is down to the low thousands, pressed by habitat clearing, hotter fires, mining, and its own low breeding rate.
Palm Cockatoo: common questions
Do palm cockatoos really use tools?
Yes, and in an unusual way. Rather than using a tool to get food, as some other parrots and crows do, a male palm cockatoo makes a tool to produce sound. He snaps off a stick roughly 20 cm long, or sometimes a hard seed pod, strips and trims it with his bill, then holds it in one foot and strikes it repeatedly against a dead branch or the rim of a hollow, creating an audible drumbeat. Females also occasionally drum. Long-term study on Cape York has shown that each male has a signature rhythm and tempo he keeps for years, which suggests the drumming carries individual identity, much like a bird's song.
Why is the palm cockatoo's bill so large?
Because its food is hard. The bird specialises in cracking very tough nuts and seeds, including pandanus keys and kanari nuts, that most animals cannot open. The bill is the largest of any parrot relative to head size, and the upper and lower parts are so long they do not close at the tip. The cockatoo compensates by wedging a nut against the bony roof of its mouth, holding it there with a strong tongue, often placing a chewed leaf or piece of wood between nut and bill as a non-slip pad, and then rasping through the shell with the lower mandible. It is effectively a hand-held nutcracker.
What do the red cheek patches do?
The bare patch of skin on each side of the face changes colour with the bird's state of arousal. When a palm cockatoo is relaxed the skin is a fairly dull pinkish red; when it is excited, courting, alarmed, or aggressive, blood flow increases and the patch flushes a bright scarlet. Because the rest of the bird is uniform smoky black, this blush is highly visible to other cockatoos and works as a fast, honest signal of mood during displays and confrontations, complementing the raised crest and spread wings.
Why is the palm cockatoo declining?
Mainly a combination of slow breeding and habitat pressure. Palm cockatoos need large old trees with deep hollows for nesting, and they raise very few young, often less than one chick every two years per pair, so losses are hard to replace. On Cape York, clearing and more frequent, hotter fires are reducing the supply of suitable nest and food trees, and bauxite mining affects part of the range. Across New Guinea, logging and forest clearance are the main threats, along with some trapping for the international cage-bird trade, where the species commands very high prices.