Palm cockatoo (Probosciger aterrimus) leaf clamping

Today’s post concentrates on a single report of animal tool use from more than 150 years ago. The account is by one of the nineteenth century’s great explorers, an Englishman whose global travels allowed him to work out the principles by which new species arise through competition and isolation.

I’m speaking, of course, of Alfred Russell Wallace.

A firm grip

Wallace dedicated his 1869 book The Malay Archipelago to his fellow evolution enthusiast, Charles Darwin:

Not only as a token of personal esteem and friendship, but also to express my deep admiration for his genius and his works.

There’s a fair bit of modesty there, because Wallace was Darwin’s equal as a naturalist, and arguably more accomplished as a collector of animal specimens. His travels to the Malay Peninsula, roaming through and around modern Indonesia and New Guinea, netted him over 125,000 insects, shells, reptiles, mammals and birds, many of them new to western science.

In the extract from his book that we’re looking at today, Wallace is in the Aru Islands, some time between March and May 1857. Here’s his map of the islands, which are located in the Arafura Sea between Australia to the south and West Papua to the north:

We join 34-year-old Alfred in a contemplative mood, listening to the birds in a growing dawn chorus and shaking his head in wonder at the unlikelihood of his being there, in ‘these almost fairy realms’. He’s snapped out of his reveries by his companions, and switches attention to the first black (or palm) cockatoo he’s seen. It’s a dead specimen, sadly, but Wallace makes the most of the opportunity to jot down his notes on the bird’s feeding habits. Especially the unique way that these birds crack the tough kanary (Canarium sp.) nuts: using a leaf tool.

I’ll let him tell it:

At early morn, before the sun has risen, we hear a loud cry of "Wawk—wawk—wawk, wŏk—wŏk—wŏk," which resounds through the forest, changing its direction, continually. This is the Great Bird of Paradise going to seek his breakfast. Others soon follow his example; lories and parroquets cry shrilly, cockatoos scream, king-hunters croak and bark, and the various smaller birds chirp and whistle their morning song.

As I lie listening to these interesting sounds, I realize my position as the first European who has ever lived for months together in the Aru islands, a place which I had hoped rather than expected ever to visit. I think how many besides myself have longed to reach these almost fairy realms, and to see with their own eyes the many wonderful and beautiful things which I am daily encountering.

But now Ali and Baderoon are up and getting ready their guns and ammunition, and little Baso has his fire lighted and is boiling my coffee, and I remember that I had a black cockatoo brought in late last night, which I must skin immediately, and so I jump up and begin my day's work very happily.

This cockatoo is the first I have seen, and is a great prize. It has a rather small and weak body, long weak legs, large wings, and an enormously developed head, ornamented with a magnificent crest, and armed with a sharp-pointed hooked bill of immense size and strength. The plumage is entirely black, but has all over it the curious powdery white secretion characteristic of cockatoos. The cheeks are bare, and of an intense blood-red colour. Instead of the harsh scream of the white cockatoos, its voice is a somewhat plaintive whistle. The tongue is a curious organ, being a slender fleshy cylinder of a deep red colour, terminated by a horny black plate, furrowed across and somewhat prehensile. The whole tongue has a considerable extensile power.

I will here relate something of the habits of this bird, with which I have since become acquainted. It frequents the lower parts of the forest, and is seen singly, or at most two or three together. It flies slowly and noiselessly, and may be killed by a comparatively slight wound. It eats various fruits and seeds, but seems more particularly attached to the kernel of the kanary-nut, which grows on a lofty forest tree (Canarium commune), abundant in the islands where this bird is found; and the manner in which it gets at these seeds shows a correlation of structure and habits, which would point out the "kanary" as its special food.

The shell of this nut is so excessively hard that only a heavy hammer will crack it; it is somewhat triangular, and the outside is quite smooth. The manner in which the bird opens these nuts is very curious. Taking one endways in its bill and keeping it firm by a pressure of the tongue, it cuts a transverse notch by a lateral sawing motion of the sharp-edged lower mandible. This done, it takes hold of the nut with its foot, and biting off a piece of leaf retains it in the deep notch of the upper mandible, and again seizing the nut, which is prevented from slipping by the elastic tissue of the leaf, fixes the edge of the lower mandible in the notch, and by a powerful nip breaks off a piece of the shell. Again taking the nut in its claws, it inserts the very long and sharp point of the bill and picks out the kernel, which is seized hold of, morsel by morsel, by the extensible tongue.

Thus every detail of form and structure in the extraordinary bill of this bird seems to have its use, and we may easily conceive that the black cockatoos have maintained themselves in competition with their more active and more numerous white allies, by their power of existing on a kind of food which no other bird is able to extract from its stony shell.

There you have it. The cockatoo gains an advantage over other birds by making and holding a small leaf tool inside of the upper part of its beak, which clamps the nut in place while it is spilt.

Wallace provides us with a drawing of the black cockatoo’s head—that’s it at the top of this post—but no images of the tool use. However, research on the nearby Tanimbar Islands might give us a clue to the kind of activity going on. This island group is only a few hundred kilometres southwest of the Aru Islands, as the cockatoo flies, and scientists there have been doing important work with local manik tilgnoi, or Goffin’s cockatoos (Cacatua goffiniana).

These dedicated bird-watchers, led by Berenika Mioduszewska and Mark O’Hara from the University of Veterinary Medicine in Vienna, have found that wild manik tilgnoi flexibly make and use small stick tools to access hidden parts of their fruit diet. Each twig tool is only a few centimetres long, and can be held in different positions in the beak, including firmly against the upper mandible just as Wallace described for the palm cockatoo:

What should we make of Wallace’s report? Whether or not palm cockatoos in the Aru Islands still make and use leaf tools, as they apparently did in the mid-nineteenth century, is unknown. It could be that only a small group, or a few innovative individuals, performed the behaviour before it fell out of favour. Or every cockatoo could be still munching away on Canarium nuts with a hidden beak glove. We’ve seen in an earlier post that wild palm cockatoos in northern Australia use stick tools for a different purpose, as drumsticks, so tool use is not completely atypical for this species.

It’s extremely difficult to spot the manufacture and use of small plant tools by wild forest birds, especially when normal feeding movements are quite similar. The Tanimbar researchers know this all too well, but that’s no reason to give up. After all, even large animals are hard to follow in the trees:

Owing to the covert characteristics of wild Goffin tool use, a purely opportunistic direct observation of this behaviour in the tropical forest would be either highly unlikely or even impossible. Indeed, the field observations conducted so far (518 hours of scanning effort resulting in 95 hours of direct observations) might not have been sufficient for uncovering tool use in the dense tropical forest. Similarly, years of intense fieldwork and focal observations were required before tool manufacture, and complex tool use was recorded in another Indonesian arboreal species, the orangutan.

As always, stay tuned, and watch the skies…

Sources: Wallace, A.R. (1869) The Malay Archipelago: The land of the orang-utan, and the bird of paradise. A narrative of travel, with studies of man and nature. 2 volumes. Macmillan and Co., London. || O’Hara, M., B. Mioduszewska, et al. (2021) Wild Goffin’s cockatoos flexibly manufacture and use tool sets. Current Biology 31:4512-4520. || Mioduszewska, B., et al. (2022) Treasure islands: foraging ecology and the emergence of tool use in wild Goffin’s cockatoos. Current Opinion in Behavioral Sciences 45:101118.

Main image credit: T.W. Wood in Wallace (1869), vol. II || Second image credit: Wallace (1869), vol. II || Third image credit: Mark O’Hara in Mioduszewska et al. (2022)