After reading my latest post concerning how much force a pileated woodpecker can endure without harming itself a fellow blogger chastised me for not explaining how this is possible. In hindsight, I indeed did leave a major part of the story untold.
There is no simple answer to this question. The truth of the matter is a number different factors work together to enable a woodpecker is able to hammer a tree with a force some 1,000 times the force of gravity without injuring itself. To begin with, the woodpecker’s brain is oriented in such a manner that it is better able to absorb force from the front. In comparison, the human brain is far better able to cope with forces from below. The woodpecker’s brain also fits tightly into its cranium. This prevents the brain from easily moving about. The woodpecker’s aspect of the woodpecker’s hyoid bone also plays a critical role. This bone actually loops around the head of the woodpecker and helps dampen the force exerted on the bird when it hammers into the wood of a tree. A number of “spongy” plate-like bones found in different spots in the skull help spread out the force of a hammer-like blow.
The design of the bill is also important. Upon close examination it is obvious that the lower bill is a bit larger that the upper bill. Why is this important? Since the upper mandible is shorter than the lower mandible the force of the bill striking the wood passes through lower jaw before it reaches the bird’s skull. Whereas the force exerted on the upper bill is cushioned by spongy bones found at its base.
The fact that the woodpecker’s chisel-like bill is self-sharpening is also an important asset. Since is bird’s bill is always sharp the bird can hammer into wood using less force than would be required if its bill was dull.
It is also important that the woodpecker make every attempt to strike its bill directly at the wood. This helps ensure that the force of the strike originates from the same direction.
It is also important that woodpeckers possess strong neck muscles.
Research conducted by Chinese scientists was able to quantify how successful the complex design of the woodpecker’s head is in muting the extremely high forces it has to withstand. Their findings demonstrated that these modifications are so effective in transferring forces down the woodpecker’s body the head receives only 0.3 percent of the initial force of a blow. That is remarkable.