The brain circuitry that allows birds to learn songs is active when woodpeckers drum on trees, suggesting the abilities may have arisen from similar evolutionary processes
September 20, 2022
To a woodpecker’s brain, drumming against a tree is a lot like birdsong. The findings reveal substantial similarities in the brain circuitry behind hearing and performing these two important acoustic activities in birds, meaning they may be alterations of a shared evolutionary template.
For some birds, vocalizations come naturally – a hawk doesn’t need to learn how to screech, for example. Songbirds and parrots, on the other hand, have to listen to and mimic older birds to produce their tunes, and special circuits in the brain allow them to do this. Erich Jarvis of Rockefeller University in New York wanted to know if the brains of birds that don’t learn their calls — flamingos, hawks, and others — looked different from those that do. Previous research had shown that the activity of a gene called parvalbumin is enhanced in special regions in the forebrains of song-learning birds compared to non-learners. Jarvis wanted to confirm that this was indeed the case with a wider variety of non-learners.
He and his colleagues analyzed the brains of seven such bird species and were surprised to find that one of them had these parvalbumin-rich areas in the brain: the false woodpecker (Dryobates pubescens).
Woodpeckers don’t just use their beaks to drill for larvae in tree trunks. They hammer at trees to create specific sound patterns that communicate territorial information to other woodpeckers. Jarvis and Matthew Fuxjager of Brown University in Rhode Island then led a team trying to see if the woodpeckers’ curious brain regions were related to drumming or to the bird’s simple vocalizations.
The researchers played drum sounds on speakers near the nest cavities of 15 wild downy woodpeckers and then examined their forebrains.
In the birds that heard drumming and drumming in response, the researchers found important genetic markers for recently increased activity in an area of the forebrain involved in learning and singing in song-learning birds. They did not find this in individuals who simply shouted a “neigh” in response, a common response among woodpeckers hearing another’s drumming.
“Brain circuits for complex acoustic communication — whether the sounds are made with the vocal organ or the beak — can have a limited way of evolving,” Jarvis says.
The researchers think birdsong and drumming may have both evolved from “evolutionary tinkering” in an ancient set of connections in the forebrain of birds for fine movements in display behavior.
The findings also suggest that drumming behavior can be at least partially learned, Jarvis says.
Nicole Creanza of Vanderbilt University in Tennessee says it would be interesting to see an even broader brain sample on the bird’s tree of life. Other displays can be studied for links to the motor learning areas, she adds, such as the elaborate courtship dances of birds of paradise and manakins.
Reference magazine: PLOS BiologyDOI: 10.1371/journal.pbio.3001751
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