Discovery about bird brains sheds light on why woodpeckers peck

By Mark Waghorn via SWNS

Drumming in woodpeckers - nature's headbangers - is neurologically similar to singing in other birds, according to new research.

Their forebrain contains specialized pecking regions that resemble those associated with song and language systems.

Woodpeckers are a diverse species known for their 'drumming' behavior, in which they perch vertically on trees and slam their beaks into the trunks, boring holes in the bark.

They forage this way, and carve out cavities for nesting and caching food. But audible drumming has evolved in the same way as vocal learning in animals and language in humans.

The study found instead of being related to vocalization, activity in these brain regions is related to the characteristic tree drumming that gives woodpeckers their name.

Language and birdsong have many similarities. Both are learned when young, require complex muscle coordination and are controlled by specialized neurons.

Both humans and songbirds express a marker gene in these regions called PV (parvalbumin).

It has never been found in discrete nuclei within the forebrain of birds that do not learn their vocalizations. But the US team surprisingly found woodpeckers also have them.

These areas are similar in number and location to several of the forebrain nuclei that control song learning and production in songbirds.

They checked for PV gene expression in several types of birds that had not previously been examined - including flamingos, ducks and penguins.

In open field tests with woodpeckers, the researchers discovered the birds' behavior that triggered brain activity in these regions was actually their rapid drumming - and not their vocalizations.

Lead author Professor Matthew Fuxjager, of Brown University, Providence, Rhode Island, said: "Woodpeckers have a set of specialized brain areas that control their ability to drum, or rapidly hammer their bill on trees, and gutters, during fights with other birds.

"Furthermore, these brain areas look remarkably similar to the parts of the brain in songbirds that help these animals learn to sing."

Like birdsong, woodpecker drumming is used to defend territories, requires rapid and complex motor movements, and must be adaptable when birds compete with each other.

Scientists have not yet established drumming is a learned behavior. But this new evidence from the brain predicts it is.

Finding this system for non-vocal communication that is both neurologically and functionally similar to the song system can help us understand how existing brain systems evolve and become co-opted for new, but similar functions.

Different species have different drumming patterns that have diverged over time, varying in features such as rhythmic structure and timing.

Recent research exploring the processes that shape woodpecker drumming has provided new insights into the complexity of this bizarre and specialized head banging.

In a courtship context, males evolve drums to entice females to mate - the sexier, the better.

In a territorial context, drumming is about staking claim to an area and scaring off potential intruders - the more threatening, the better.

Drums encode identity, so they evolve to ensure birds can recognize their own species - the more distinct, the better.

A sound that travels far and cuts through background noise will reach more neighboring birds - the louder and clearer, the better.

But there is a downside to conspicuousness. Drums that are loud and clear are also more likely to be intercepted by eavesdropping predators.

Choosing the right tree matters. Trunk diameter, bark density and tree condition all affect the sound.

Physical traits such as beaks and necks, along with the trees themselves, comprise the percussive instruments woodpeckers use to produce their communication signals.

So these are also implicated in the evolutionary tug-of-war that shapes woodpecker drums.

The findings were published in the journal PLOS Biology.