Songbirds are popular for their mellow tones, but drummers can start stealing some of that limelight.
Woodpeckers, which don’t sing but drum on trees, have brain regions similar to those of songbirds, researchers report March 20 PLOS biology. The finding is surprising since songbirds use these regions to learn their songs at an early age, but it is not clear whether woodpeckers learn their drumbeats (SN: 9/16/21). Woodpeckers or not, the result points to a common evolutionary origin for song and drums.
The ability to learn sounds by listening to them, just like humans do when they learn to speak, is a rare trait in the animal kingdom. Song learners like songbirds, hummingbirds and parrots have independently evolved distinct clusters of nerve cells called nuclei in their forebrain that control the ability. Animals that don’t learn aloud are believed to lack these brain traits.
While it’s widely believed that other birds don’t have these cell nuclei, “there are thousands of birds in the world,” says Matthew Fuxjager, a biologist at Brown University in Providence, RI. “While we say that these brain regions only exist in these small groups of species, no one has really looked at many of these other taxa.
Fuxjager and his colleagues examined the noggins of several birds that do not learn vocally to see if they really lacked these brain nuclei. Using molecular probes, the team checked the birds’ brains for the activity of a gene called parvalbumin, a well-known marker of vocal learning nuclei. Many of the birds, including penguins and flamingos, came up short, but there was one exception — male and female woodpeckers, who had three dots in their brains high parvalbumin Activity.
Although woodpeckers don’t sing, they are quick to drum on trees and gullies to defend their territory or to find mates. This drumming is different from the drilling that birds do to find food. When the team found songbird-like brain nuclei in woodpeckers, Fuxjager was immediately intrigued. “I immediately thought it probably had something to do with playing the drums,” he says.
The researchers put downy woodpeckers (Dryobates pubescens) in the wild to audio recordings of other woodpeckers drumming. This faux territorial invasion elicited an aggressive drumming response from the birds, which were then captured and euthanized to have their recent brain activity analyzed. In fact, the same regions identified by previous lab tests had been activated in the drummers.
The brains of bird singers and drummers evolved separately, but the similarity of the regions analyzed points to a common origin. “It suggests that there are common themes in how you evolve these complex behaviors,” says Bradley Colquitt, a biologist at the University of California, Santa Cruz who was not involved in the study. The neural circuits formed by these nuclei most likely evolved from an ancestral circuit that controls movement, Colquitt says.
“Birdsong is basically the brain controlling the muscles in a vocal organ called the syrinx,” says Fuxjager. These ingenious movements are not dissimilar to the rapid head and neck movements of drumming.
Whether drumming is learned like birdsong remains an open question, which the team is now investigating. Future work will also look at how woodpecker brains are wired, how these nuclei control drumming, and how the role of brain regions in drumming has evolved in different woodpecker species, Fuxjager says.
This new study “discovers another species that we can add to our comparative efforts” to better understand how complex behaviors evolve, Colquitt says. “It’s a preview of a potentially exciting evolutionary neurobiology.” Now that woodpeckers have joined the band of important musical birds, it looks like the drummers may soon get their chance to shine.