The Woodpecker's Beak

Of the 14 species of woodpeckers (including sapsuckers, which are woodpeckers that specialize in feeding on sap) that are found in California, 12 can be seen here in the San Bernardino Mountains.

The structure and anatomy of a woodpecker’s tongue is a marvel of nature. We’ll get into that in a moment, but first a review of a few of our local species.

The one that many people are most familiar with is a year-round resident known as the acorn woodpecker. Its raucous calls often punctuate the quiet mornings as it darts from tree to tree. Even without binoculars, the white wing patches can be easily seen to identify this bird. As the name implies, acorns play an important role in this species’ life. These birds drill holes in the trunks of trees, collect acorns, and shove them into these holes to create a storage “granaries” often to be eaten during colder weather when there are fewer insects to eat.

Much to the dismay of some homeowners, acorn woodpeckers sometimes decide to turn the side of your house into a granary. The damage they do when making holes for a secure place to store their acorns can be substantial.

Another common woodpecker here in the mountains is the northern flicker. This is our largest woodpecker and can be recognized by its white rump as it flies as well as the crimson lining of the underside of the wings. Interestingly, flickers in the eastern US have yellow coloration in the wings instead of red.

One of the most interesting species here in the mountains is a cold-weather visitor called Lewis’s woodpecker. Like acorn woodpeckers, they occur in loose flocks and sometimes even store acorns. Their coloration is somewhat unusual. The have iridescent dark green backs with a red face and pink bellies.

So, what’s so special about a woodpecker’s tongue? They are long. Really long. In fact, one of the longest tongues of any bird species belongs to our northern flicker. It can extend two inches (5 centimeters) beyond the tip of the beak! Where is all that “extra tongue” stored when not in use? This is where it gets really interesting. Inside the mouth, the base of the tongue bifurcates (splits)

Tongue and hyoid apparatus highlighted in red.

into something called the hyoid apparatus that has a right and left side that extends along the base of the jaw and then wraps up around the top of the skull down to the nostrils. The hyoid apparatus can slide back and forth, allowing the bird to extend the tongue far beyond the tip of its beak. Many researchers believe this structure serves as a “shock absorber” for the skull to protect the brain from concussion as the bird hammers on a tree.

It has been estimated that the g-forces the woodpecker’s skull experiences while drilling are 10 times greater than what would cause a concussion in humans. However, a recent study suggests that having a shock absorber would inhibit the woodpecker’s ability to effectively excavate wood. Using high-speed videography, they demonstrated there is no shock absorbing effect and the reason a woodpecker doesn’t get a concussion (or a headache!) is because of its small brain size. The smaller the brain mass, the less force it would experience while pecking.

But that’s not all that makes a woodpecker’s tongue unique. The elongated tongue is an adaptation for feeding; it helps extract food from the holes they drill. But, the tongue is further adapted based on the species’ diet. Flickers are often seen on the ground because they feed largely on ants. When they extend their tongue to feed, it is coated with a sticky saliva that is created by salivary glands located close to the tip of the beak. The sticky saliva on the tongue catches the ants and then the tongue retracts toward the back of the throat, where a where a different type of saliva provides lubrication that aids in swallowing.

Most woodpecker species have barbs on the tip of the tongue that help secure prey. Sapsuckers, on the other hand, don’t feed primarily on insects. Their tongue structure is adapted to their specific diet of tree sap. Instead of barbs, their tongue is equipped with a fur-like structure that resembles the bristles of a paintbrush. This adaptation helps maximize the amount of sap the tongue can collect.

These evolutionary adaptations are nothing short of amazing. Just one of the many facets that makes birds such intriguing creatures.