Songbirds get a lot of love for their sweet tones, but drummers can start to steal some of that limelight.
Woodpeckers, which do not sing but drum on the trees, have brain regions that are similar to those of songbirdsresearchers report on September 20 in PLOS Biology. The finding is surprising because songbirds use these regions to learn their songs at a young age, but it is unclear whether woodpeckers learn to drum (Serial number: 09/16/21). Whether or not woodpeckers do, the result suggests a shared evolutionary origin for both song and drumming.
The ability to learn vocalizations by hearing them, much like humans learn to speak, is a rare trait in the animal kingdom. Vocal learners, such as songbirds, hummingbirds, and parrots, have independently developed certain groups of nerve cells called nuclei in their forebrains that control ability. Animals that do not learn vocally are thought to lack these brain features.
While it’s commonly assumed that other birds don’t have these nuclei, “there are thousands of birds in the world,” says Matthew Fuxjager, a biologist at Brown University in Providence, Rhode Island. “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 heads of several vocally non-learner birds to see if they really lacked these brain nuclei. Using molecular probes, the team scanned the birds’ brains for activity of a gene called parvalbumin, a known marker of vocal learning nuclei. Many of the birds, including penguins and flamingos, fell short, but there was one exception: male and female woodpeckers, which had three points in the brain with high parvalbumin exercise.
Although woodpeckers do not sing, they do make a rapid drumbeat on trees and house gutters to defend their territories or find a mate. 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 was probably related to drumming,” he says.
The researchers subjected downy woodpeckers (Dryobates pubescens) in the wild to audio recordings of drumming by other woodpeckers. This false territorial invasion provoked an aggressive drumming response from the birds, which were then captured and euthanized to analyze their recent brain activity. Sure enough, the same regions identified by earlier lab tests had been activated in the drummers.
The brains of bird singers and drummers evolved separately, but the similarity of the regions analyzed hints at a common origin. “It suggests there are common themes about how these complex behaviors develop,” says Bradley Colquitt, a biologist at the University of California, Santa Cruz, who was not involved in the study. The neural circuitry formed by these nuclei likely developed from an ancestral circuitry that controls movement, says Colquitt.
“Birdsong is basically the brain controlling the muscles in a vocal organ called the syrinx,” says Fuxjager. These sophisticated movements are not unlike the rapid movements of the head and neck that are made when playing the drums.
Whether drumming is learned like birdsong remains an open question that the team is now exploring. 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 evolved among woodpecker species, says Fuxjager.
This new study “uncovers another species that we can add to our comparative efforts” to better understand how complex behaviors evolve, says Colquitt. “It’s a potentially exciting preview of evolutionary neurobiology.” Now that the woodpeckers have joined the band of important musical birds, it looks like the drummers will soon have their chance to shine.