New understanding of how woodpeckers pound trees

One of the great pleasures of winter is listening to the drumming woodpeckers. Their noisy tattoos echoing across a frigid and otherwise silent northern landscape fill me with hope that winter will eventually end, even as I marvel at the adaptations that allow these splendid birds to slap their faces against wood. solid wood.

Natural selection would obviously favor physiological and morphological changes that protect woodpeckers from concussions and long-term brain damage. But natural selection must also favor adaptations that make their pecks as strong as possible and their hammering as powerful as possible to dig up insects deep in the wood and dig out nesting and resting cavities. The needs for protection and power seem diametrically opposed.

Traditionally, people have focused more on understanding the adaptations that protect the brains from woodpeckers than those that make them powerful hammers. Indeed, some engineers have incorporated elements of woodpecker anatomy into the design of football helmets. One of the most read articles on BirdWatchingDaily.com, written by the late Eldon Greij in 2013, is called “Why Woodpeckers Can Hammer Without Getting a Headache,” an overview of how scientists hypothesized that l The anatomy of the woodpecker protects the brain.

But how well protected is a woodpecker’s brain? In a follow-up column in 2021, “Understanding Potential Brain Damage in Woodpeckers,” Greij reviewed a 2018 study from Boston University School of Medicine in which researchers examined the brain tissue of woodpeckers and woodpeckers. blackbirds in search of the protein associated with chronic traumatic encephalopathy (CTE). in footballers who have suffered repeated head trauma. They found that eight of ten peaks examined were positive for this protein, hyperphosphorylated tau, which is also implicated in other irreversible degenerative diseases in humans, such as dementia, Alzheimer’s disease and Alzheimer’s disease. Parkinson’s. None of the ten Red-winged Blackbird brains examined showed any trace of this protein. Could woodpeckers have developed a biochemical mechanism to counteract its effects?

Today, a brand new study published in Current biology shows, via extraordinary slow-motion photography, that the woodpecker’s beak and skull are designed to function as a single unit, a “rigid hammer to improve pecking performance, not as a shock absorption system to protect the brain “. By looking at specific markers, the study established that the beak and head stopped at exactly the same time, both experiencing the same impact force. Speculation that something between the beak and the skull serves as a shock absorber does not hold up.

After my son was in a motorcycle accident, I examined his helmet. The outer shell was cracked, but the inner padding had protected his head from injury, unlike his unprotected body. It may be that, as Greij wrote in his 2013 paper, much of the protection of a woodpecker’s brain is due to what lies beneath the skull, perhaps involving the neck muscles, some of the exceptionally well developed hyoid apparatus which supports the long tongue. by wrapping around the skull and reducing the space in the skull to reduce the risk of brain “sloshing”, just as a helmet must fit properly to protect an athlete or cyclist from head injury.

This image is a reconstruction of the skull of a black woodpecker from a CT scan. A well-developed area of ​​spongy bone in the frontal region of the skull, thought to absorb shock, is highlighted in green. Image credit: Christine Böhmer (Christian-Albrechts-Universität zu Kiel) and Anick Abourachid (National Museum of Natural History)

We have no way of asking woodpeckers how they feel after drumming, so asking why they don’t have headaches may be based on a faulty assumption. We know that they can have quite a long life: one banded Pileated Woodpecker has been known to survive at least 12 years and 11 months, and two banded Hairy Woodpeckers have lived more than 15 years. How woodpeckers not only survive but apparently thrive with the same protein in their brains linked to life-shortening conditions in humans is an important question for ornithologists and medical researchers.

The new study, establishing just how hard a woodpecker’s body is designed to pound the body of a woodpecker, accomplishes what the best scientific research does: it leaves us with more new questions and new lines of inquiry than simple answers. And this study does something more. Watching the researchers’ slow-motion video of a pileated woodpecker striking wood, recorded at 1,600 frames per second and broadcast at 30 frames per second, is as stunning and enjoyable as it is enlightening.

Watch a video of the woodpecker study

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