Drumming cockatoos and the rhythms of love

Whales and songbirds produce sounds resembling human music, and chimpanzees and crows use tools. But only one nonhuman animal is known to marry these two skills. Palm cockatoos from northern Australia modify sticks and pods and use them to drum regular rhythms, according to new research published in Science Advances. In most cases, males drop beats in the presence of females, suggesting they perform the skill to show off to mates. The birds even have their own signature cadences, not unlike human musicians.

This example is “the closest we have so far to musical instrument use and rhythm in humans,” said Robert Heinsohn, a professor of evolutionary and conservation biology at the Australian National University and an author of the paper. A palm cockatoo drumming performance starts with instrument fashioning — an opportunity to show off beak strength and cleverness (the birds are incredibly intelligent). Often, as a female is watching, a male will ostentatiously break a hefty stick off a tree and trim it to about the length of a pencil.

Holding the stick, or occasionally a hard seedpod, with his left foot (parrots are typically left-footed), the male taps a beat on his tree perch. Occasionally, he mixes in a whistle or other sounds from an impressive repertoire of around 20 syllables. As he grows more aroused, the crest feathers on his head become erect. Spreading his wings, he pirouettes and bobs his head deeply, like an expressive pianist. He uncovers his red cheek patches — the only swaths of colour on his otherwise black body — and they fill with blood, brightening like a blush.

Over seven years, Robert and his collaborators collected audio and video recordings of 18 male palm cockatoos exhibiting such behaviours in Australia’s Cape York Peninsula, where the birds are considered vulnerable because of aluminium ore mining.

Cultural habit

Though palm cockatoos also live in Papua New Guinea and Indonesia, they have been observed drumming only in Cape York Peninsula, which suggests the habit is cultural. “Presumably some bright spark of a male stumbled across this behaviour, females found it pleasing and it took off in the population,” Robert said.

Because they are shy, palm cockatoos are difficult to study. Trekking to the rain forest’s edge, the researchers looked for palm cockatoos in hollow eucalyptus trees. They managed to catch a drumming event about once every 100 hours, said Christina Zdenek, a PhD candidate at the University of Queensland, Australia who led the fieldwork for the study.

Analysing 131 drumming sequences, the scientists found that the birds produced regular, predictable rhythms, rather than random thumps. Individual males differed significantly in percussive styles. One that the researchers named Ringo Starr (there was also a Phil Collins) liked to start with a rapid flourish, then settle into a consistent beat, occasionally going on for as long as 14 minutes.

Nearly 70% of the time, males drummed with a female present. Palm cockatoos are mostly monogamous, but males have to keep proving themselves to choosy females — on an average, palm cockatoo pairs successfully fledge a chick only once every decade, so the stakes are high.

The researchers don’t yet know whether females prefer certain rhythms over others. But if a male is delivering an effective performance, the female comes over and mirrors his movements. The birds sway together and gently preen each other’s feathers, an act of pair-bonding that helps them prepare for breeding.

The findings make Robert wonder whether human rhythm also originated as a courtship display.

“Maybe that’s how it got started, and later on it evolved into our love for group-based dancing and music,” he said. Other researchers aren’t convinced. “I don’t know if it’s such a direct comparison,” said Michelle Spierings, a postdoctoral researcher who studies music perception in animals. There are many other hypotheses about the origin of human rhythm. Nevertheless, if scientists manage to identify and study other species that drum, the answer may loom closer, Michelle believes. “This is a great first example,” she said.