������ý

Cockatoos can understand that they need to bring a two-piece “toolkit” to retrieve a cashew nut treat.

This makes them only the second non-human animal, after chimpanzees, that seems to view multiple tools as being part of a set needed to achieve a single goal.

Goffin’s cockatoos (Cacatua goffiniana) are small, white parrots from Indonesia. In captivity, the birds have been seen using three human-made tools to retrieve seeds from inside a fruit stone: one for cutting the stone, a sturdier tool for wedging open a crack and a third one for scooping out the seeds.

But it was unclear if the birds understand that all three items are part of a set or if they just used each tool in turn as the need arose, says at the University of Veterinary Medicine Vienna in Austria.

Osuna-Mascaró’s team presented cockatoos with a cashew nut, held in a box behind a transparent cover. To get it, the birds first had to use a short, pointed stick to puncture the cover, then use a longer straw to retrieve the nut. Seven out of 10 birds worked out how to do this.

But did the birds see the two items as part of a set? To find out, five of the successful birds were tested again. This time, the team placed the box higher up than the offered tools, so the cockatoos had to make a short but arduous vertical flight to transport them. Four of the birds learned to take the two tools to the box in one trip.

“They are using the tools as something more than the sum of their parts,” says Osuna-Mascaró. “Many animals use tools, but they use them in a rigid way depending on their innate behaviours. Other animals are able to use tools in flexible ways to solve novel problems.”

Some chimps are also able to use multiple tools. When “fishing” for termites in the insects’ large mounds, they use a short, rigid stick to make a hole in the nest, then push a long, flexible stick into the mound, which the termites bite onto. Chimps also bring both kinds of stick to the termite mounds, when needed.

“We know that brain size is not a good indicator of intelligence,” says at the University of Oxford. “The Goffin’s cockatoos are probably not unique [among birds] – it’s simply that they have been studied.”

Sign up to Wild Wild Life, a free monthly newsletter celebrating the diversity and science of animals, plants and Earth’s other weird and wonderful inhabitants