The incessant drumming of a woodpecker on a hollow tree can be an annoying distraction for anyone who has to listen to it. To other woodpeckers, however, it’s as distinct and as telling as any birdsong.
A new study, published last week in the journal PLOS Biology, found that a woodpecker’s drumming and a songbird’s singing are governed by similar specialized structures in the birds’ brains, structures that aren’t found in those of other nonsinging birds. And both behaviors serve the same purposes of marking out territory and attracting mates, the researchers said.
The findings are especially intriguing because the singing of songbirds has important parallels to human speech, so the drumming of woodpeckers could now, too, give new scientific insights into how humans talk.
“Woodpeckers use drumming as songbirds use song,” said a senior author of the new research, evolutionary biologist Matthew Fuxjager, an associate professor of ecology, evolution and organismal biology at Brown University in Providence, Rhode Island. “The structures are similar in size and shape and are similar in terms of where we find them in the brain.”
The research combines two approaches to the study of woodpeckers: work by Fuxjager into their ecology and work by his collaborator, Erich Jarvis, a professor of neurogenetics at Rockefeller University in New York, into the genetic mechanisms at play.
The researchers found that drumming by woodpeckers and singing by songbirds are governed by very similar structures in the forebrains of the animals, made of cells that strongly express the protein parvalbumin.
“When you study songbirds, hummingbirds and parrots, you find areas that control vocal learning express parvalbumin more than other parts of the brain,” Fuxjager said.
He noted that structures of cells that strongly express parvalbumin are also seen in human brains but that they aren’t seen in birds that don’t communicate with vocalizations.
It was a surprise, therefore, when the research led by Fuxjager and Jarvis found such structures in the woodpecker brains but not in those of birds that don’t sing, such as emus, penguins and ducks (quacks don’t count).
Fuxjager suggested in the study that both the singing and the drumming originated in specialized brain structures for refined motor control in the ancestors of modern birds.
Although they might sound quite different, the behaviors are remarkably similar. Both involve complex muscle coordination, and both are used to mark out territory to competitors, which can hear the drumming or singing from afar.
Both drumming and singing are also used as courtship signals when males hope to attract mates. Future studies will look for other similarities, such as whether the patterns of woodpecker drumming are learned at an early age, like the singing of songbirds, he said.
Fuxjager noted that there are more than 200 species of woodpecker around the world on every continent except Australia.
Every species of woodpecker drums in short bursts with specific rhythms and at specific speeds, depending on what they want to communicate and to whom.
If woodpeckers don’t get their drumming patterns right, it will be noticed by other woodpeckers of that species, which use them to assess whether an individual is a worthy competitor. If they get them wrong, however, other woodpeckers won’t be able to recognize them or understand them.
Drumming also has certain advantages over singing, because it has other uses: It’s used to reveal edible insects in wood and to make cavities in tree trunks for nesting.
But the drumming to find insects or make nests is much slower than the repetitive — and loud — drumming that woodpeckers use to mark out territory and attract mates, Fuxjager said.
Scientists study the singing of songbirds — and possibly now the drumming of woodpeckers — because it has parallels to human speech.
Both are learned when young, for example, but have genetic components. Both require complex muscle coordination, and both are controlled by specialized regions of the brain.
Jon Sakata, an associate professor of biology at McGill University in Montreal who specializes in the neurophysiological and behavioral mechanisms of songbird communications, noted the similarities between the forebrain structures that seem to control drumming in woodpeckers, described in the new study, and singing in songbirds. Sakata wasn’t involved in the latest study.
In both cases, structures of brain cells — neurons — that contain parvalbumin seem to be important for performing complex motor movements and for learning to produce such movements, Sakata said in an email.
“Because parvalbumin neurons are also implicated in speech production and learning, this is a wonderful example of how similar brain mechanisms can be co-opted for different behaviors across species,” he said.