What value is there in banging your head against a tree all day long?
For us, very little. For woodpeckers, plenty!
In essence, the value lies in the fact that not many other birds have access to the enormous larder of food that lies beneath the surface of the wood. This can be found in the form of termites, ants and wood borers, along with their eggs and larval stages, to name but a few.
Evolution has led to many adaptations allowing the woodpeckers to smash their heads into a tree to get a bite to eat. Now compare that to humans who have an incredibly fragile brain with very little to protect it. Despite our puny amount of protection, we still get a kick out of throwing our bodies into each other on a rugby or football field, often coming off with injuries and concussions.
Concussions are a temporary impairment of cognitive function and consciousness as a result of a hard blow to the head. Basically they occur when brain tissue is damaged after shock waves pass through it when you hit your head. A serious blow can be obvious and immediate, whereas symptoms from a sub-concussive blow may not present themselves immediately but still degenerate the brain tissue causing memory loss, aggression, confusion and deep depression years later. Most contact sports result in these repeated sub-concussive blows which can be detrimental to human health.
So how do woodpeckers, these seemingly crazy little birds, bang their heads repeatedly into a tree with way more force than that which would cause a concussion in humans, and not suffer any ill effects?
Most of the woodpeckers’ adaptions protect the brain against degeneration caused by shock from the chiseling/pounding by either absorbing it or dispersing:
– A reduced amount of cerebrospinal fluid found in the brain and spine means that there is less liquid in contact with the brain to transmit shockwaves which cause damage and disrupt the nerve functioning.
– A specially designed hinge joint between the frontal bones and the nasal bones dissipates and absorbs the shock due to the lack of direct contact between the two bones.
– At the base of the upper mandible there is a bony strengthening mechanism, basically modified frontal bones of the skull that prevent the bill from cracking off.
– Muscles at the base of the lower mandible contract a split second before impact absorbing most of the impact as well as transferring this through the base of the skull below the brain.
– And most incredible is the tongue of the woodpecker which can be as long as 15cm in some species is not only used to try fish out food from within the wooden enclosure. The tongue contributes extensively in protecting the brain. The attachment is at the base of the upper mandible just below the right eye and from here it doesn’t travel straight into the mouth. It coils within the head, wrapping up and over the top of the head, around the back and down into the mouth, and is a massive shock absorber.
With a head ready for a pounding, the woodpeckers have further adaptations that allow for their comical stress relieving habits:
The Bill is sharpened and the keratin rhamphotheca (fancy name for beak) grows throughout their life over the top of a broad bony support.
Well developed neck muscles provide the power and strength to manoeuvre the head back and forth at such high speeds. With such high speeds momentum builds; in order to keep the bird anchored in place and upright it has zygodactylous feet and a very strong tail with reinforced tail feathers. The feet have two toes facing forward and two backward, providing the best grip, and the tail is the third part to the tripod propping it up.
All these adaptations allow for access to an otherwise, untapped food source but also provide an awesome set of tools. Tools which can be used to excavate nests high up in trees away from most forms of danger and sheltered from the elements.
Thank goodness we don’t need to bang our heads into a tree to show anyone anything. I tried it once before when I was young and it didn’t end too well. My brother and I had made a rope swing from a tree and being the younger brother, I was told to test it out. He held the end of the rope, drawing it back and flung me forwards. Just like George of the Jungle, I couldn’t watch out for that tree and collided with it head first, getting knocked unconscious. Having experienced a number of successive concussions in the years after this, I feel a bit of sympathy for the woodpeckers and could have done with some of their adaptations on the rugby field!