New research busts a popular myth on why woodpeckers don’t hurt

Slow-motion video of a piled woodpecker pecking (Dryocopus Pilates) The original video was recorded at 1600 frames per second. credit: Robert Shadwick and Erika Ortlieb/University of British Columbia

Check out almost any Popular Science article about woodpeckers and you’ll find some mention of why birds don’t seem to hurt, despite energetically drumming on tree trunks all day long with their beaks. Conventional wisdom holds that the woodpecker’s skull and beak structure act as a sort of built-in shock absorber, protecting the bird from injury. But a new paper published in the journal Current Biology argues that this is wrong and that woodpecker heads behave more like hard hammers than shock absorbers.

“While filming woodpeckers in zoos, I have seen parents explain to their children that woodpeckers don’t get headaches because their heads have shock absorbers,” said co-author Sam Van Wasenberg, from the Universitt Antwerpen in Belgium. ” “This myth of shock absorption in woodpeckers is now busted with our findings.”

As to why this particular myth has been tolerated for so long, van Wasenberg tells Ars, “For us humans, the first thing that comes to our mind is when seeing an animal violently banging its head against trees. It is to be seen that the animal has some sort of built-in cushioning to prevent it from being headache or shaking. It is logical for us to think of such an action in terms of safety and security, as if it were an accident. “

The shock-absorber hypothesis did not completely lack scientific merit. (A 2022 study also won the Ig Nobel Prize in 2006. I’ve written about this topic in the past.) It started with a 1976 Lancet paper by Philip R.A. May. and others., to propose the woodpecker as a natural model to investigate the mechanism of head injury and its prevention. Other studies have shown that woodpeckers can hammer trees up to 12,000 times a day during their mating season, an average of 18 to 22 pecs per second.

in great shape , The black woodpecker that was filmed for the study was photographed in Alpenzu Innbruck, Austria.

Sam van Wasenberg / University of Antwerpi

That kind of sudden, sharp jolt can produce a deceleration force as high as 1,200 grams. A human would suffer a shock with a sudden drop of 100 grams. A 2006 study proposed that the woodpecker’s brain orientation within the skull increased the area of ​​contact when pecking, reducing stress on the brain. Given those accelerating speeds, the birds’ small size is also a boon.

Micro-CT scans have shown that the woodpecker skull boasts thick muscles in the neck, sponge-like bones and a third inner eyelid to house the eyeball, which scientists believed to absorb impact and prevent injury from constant drumming. will work together for A 2011 study found that the back of the skull also contains another springy structure called the hyoid, which may work together with cerebrospinal fluid to further suppress vibrations. Recently, a 2021 study found that the jaw system of a bird may also act as a cushion during the pecking process.

Enter Van Wasenberg, who decided to conduct his own research into the topic after being struck by the paradoxical nature of the shock absorber hypothesis. He argued that any absorption or dissipation of the head’s kinetic energy would actually reduce the bird’s ability to consistently hammer. Since this drumming behavior is so central to the woodpecker’s ability to communicate and attract mates, it was unlikely that an inherent shock absorber would have evolved through natural selection.

“There was already a long-standing suspicion in the scientific literature,” van Wasenberg said, dating all the way back to May’s 1976 paper. “May wrote, ‘If the beak absorbs more of its own impact, the unfortunate bird will have to pound even more. The notion that the woodpecker head needed to be primarily a functional hammer made sense to me. From reading the literature, it appeared to me that cranial shock absorption has never been confirmed to perform its natural behavior by living birds, a fact reported by many sources. It inspired me to research the subject.”

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