Male palm cockatoos tap out rhythms on trees to woo potential mates, and each bird makes drumsticks with its own distinctive design.
Palm cockatoos (Probosciger aterrimus) are the only known species, other than humans, to create tools that they use to make rhythmic sounds. Males in northern Australia have been observed holding either a seed pod or a small branch in their feet to tap against a tree in their drumming displays.
“What you’re looking at is totally unique in the animal world, and very analogous to what we see in humans,” says Robert Heinsohn at the Australian National University in Canberra.
After drumming, the cockatoos tend to throw away their drumsticks, so Heinsohn and his colleagues decided to track where and when these displays happened and collect the discarded tools in Kutini-Payamu National Park in Queensland. In total, they got 256 drumming tools from 70 trees.
Around 89 per cent of the tools were made from small branches, indicating a clear preference for branches over seed pods, although a small number of birds seemed to use both types.
The researchers analysed sticks made by 12 males to compare the range of designs. They found that the cockatoos had individual preferences for different kinds of drumsticks, which they created by picking up or snapping off a branch and whittling it down with their beaks. “They were very consistent in their design,” says Heinsohn. “Some like them long and skinny, or long and fat, or short and skinny, and everything in between.”
There was no evidence that neighbouring cockatoos copied each other’s designs. Instead, it might be that the birds learn what a good drumstick is from their fathers, says Heinsohn.
“Palm cockatoos are intellectually very interesting,” says team member Christina Zdenek at the University of Queensland, Australia. “This shows that each bird is an individual that has its own independent thoughts. The level of cognition to make these decisions and develop these habits shows a high degree of intelligence.”