During election season, everyone can relate to woodpeckers: We all feel like banging our heads against the wall.
The birds handle it better, though, so Weird Animal Question of the Week was pleased to look into Derek Halas’s question: “Why don’t woodpeckers get headaches?”
Little Drummer Bird
It's a tough one to answer, says Walter Koenig, an ornithologist at Cornell University, via email. But, he says, if pecking caused pain and injury, “presumably they wouldn’t be around for very long"—a hurt bird would likely succumb to predators.
There are more than 300 species of woodpeckers worldwide, and they peck wood for a variety of reasons: to excavate nest cavities, dig for insects or sap, or create holes to store food.
When selecting wood, the birds usually target trees weakened by fungal decay, which are easier to crack, Jerome Jackson, a behavioral ecologist at Florida Gulf Coast University, says via email.
The tapping is also “usually done with glancing blows—not a direct hit—thus not so hard on the woodpecker," he says. (See "Weasel Rides Woodpecker in Viral Photo—But Is It Real?")
Some woodpeckers practice drumming (watch video)—a superfast pecking that attracts mates and defends territory—on a resonant surface, like a hollow tree. That allows for a louder noise while avoiding punishing impact.
Acorn woodpeckers of North and Central America have another strategy: They carve out individual holes into trees, each just big enough to "squeeze in a single acorn"—storage for leaner times, Jackson says.
In a recent incident in California, acorn woodpeckers stashed 300 pounds of acorns into a wireless antenna, disrupting communication in nearby towns. (Watch the incredible video.)
Woodpeckers also have, well, a head for pecking.
For one, woodpeckers have tiny brains—just 0.07 ounce. The bigger the brain, the higher the mass and thus the higher the risk of brain injury, says Lorna Gibson, a professor of materials science and engineering at MIT who has studied woodpecker brains.
“Size is the most important thing,” says Gibson, an avid bird-watcher who documented her results in a video series.
Another factor that protects woodpecker noggins is the limited time the tree and their bill are in contact, she says. It's brief—just one-half to one millisecond. By comparison, a typical human head injury happens between about three and 15 milliseconds.
The woodpecker’s capacity to absorb blows has even inspired a system to reduce concussions in sports such as football.
The outside of a woodpecker's skull is made of dense bone, while the inside is porous bone, Gibson says.
The force applied during pecking is "distributed around the skull to the sturdy bone at the base and the back,” keeping the pressure off the brain, says Richard Prum, evolutionary ornithologist at Yale University, via email. (Related: "Woodpeckers Are Pros at Protecting Their Brains.")
Woodpecker brains also fit snugly in those skulls, preventing the organ from banging around. The orientation of the brain is also important, MIT's Gibson says: It sits at an angle toward the back of its head, like a half orange with the flat side facing the front. That creates more surface area to absorb those exacting blows.
A 2011 study suggested that the hyoid apparatus, a bone-and-muscle structure that wraps around a woodpecker's skull, also keeps the brain safe.
“The bottom line," Prum says, "is good evolutionary design.”