There are over 200 different species of woodpeckers in the Picidae family. They can be found around the world, each possessing a set of features that enable them to thrive in their arboreal habitats with their most notable adaptations being their strong, chisel-like beaks, specifically designed for drilling into wood.
As diverse as the species are, so are their choices in drilling materials. Acorn Woodpeckers, prefer dead trees or dead parts of live trees, while Pileated Woodpeckers prefer large mature trees. Red-headed Woodpeckers are keen on dead snags, whereas Downy Woodpeckers, the world’s smallest species of woodpecker, are drawn to naturally smaller branches or stubs protruding from the main trunk. Yet, despite their eclectic range of preference, these woodpeckers are all joined by the same remarkable anatomy.
Unlike all other birds, woodpeckers have surprisingly long tongues helping them reach deep into crevices to dig out ants, beetle larvae, and other invertebrates. But where to store such a sizeable tongue? Our tongue is attached to a horseshoe-shaped bone called the hyoid that sits under our jaw and anchors it to the floor of our mouth, but a woodpecker’s hyoid is in the bird's upper beak behind the nostrils. In a nutshell, it ravels the tongue around its own skull.
When the tongue is retracted, the tongue then splits into two and passes between the eyes and over the top of the skull, around the back, then under and back up to meet again as a single muscle at the base of the lower beak. Researchers in China recorded slow-motion footage of a Great Spotted Woodpecker as it pecked at a tree, and sensors measured the pecking force as CT scanners looked at the structures within its head. They saw that when the bird hammered, the tongue muscles contracted, tensing the tongue so that it held tightly to the skull and spine, just like a seat-belt keeps you in your seat during a collision. As a result, the birds don’t suffer a lick of harm.
For a long time, researchers believed that, in combination with this tongue ‘safety belt’, woodpeckers’ skulls behaved like a shock absorber, whose hard bony plates interlocked with spongier ones to take the force of the impact and prevent woodpeckers from dying due to brain injuries. These theories were backed up by numerous cranial studies, but it now turns out that there is something else in motion here; specifically, energy.
DESIGNED TO DRILL
According to a study from the University of Antwerp, the key to woodpeckers surviving the harsh collisions is due to how it converts the energy from the impact. When a woodpecker strikes, the energy released during the collision is converted into something called strain energy in the body. Too much strain in the head can be catastrophic. But the woodpecker’s incredibly specialized beak and skull redirects 99.7% of the strain down into the rest of the body, instead of retaining it in the head. The 0.3% left in the head dissipates in the form of heat, but as this heat then increases the temperature inside the skull, the birds have to take frequent breaks from pecking to cool down. Further studies found that woodpeckers have a special way of rotating their heads that helps to dissipate the heat, as well as taking short, shallow breaths that protect their lungs from bursting as the energy spreads through their bodies.
Woodpeckers are a marvel. From their outer beauty to their intricate anatomy which is optimised to bore into wood, woodpeckers are born to burrow. By learning more about our feathered friends, we can better appreciate what incredible creatures surround us. Next time you hear a woodpecker at work, remember that they are much more than what meets the eye.