When the woodpecker’s beak strikes an object, the high impact force at its tip is relieved by the anatomy of its beak and the spongy hyoid bone. As a result, the stress force from the impact is reduced two to eight times from the beak tip to the point where the beak meets its skull.
Of the forces that do reach the woodpecker’s skull, the unique structure of its cranial bone prevents forces from reaching its brain and cranial cavity. This cranial bone is a mixture of tightly packed, dense compact bone surrounding a deeper bone that is layered in staggered, plate-like structures that create a dense shock absorption system. When forces intersect with this deeper bone, its porous and layered structure scatters frequencies in divergent directions away from the central point of impact. This bone, while flexible, can be fragile on its own. But by being encased in compact bone, the overall system maintains flexibility within, allowing for movement that absorbs shock.
This diagram represents (A) the point of impact and (B) the point opposite impact that receives residual forces experienced at the point of impact. Illustration by Allison Miller.
The left image above represents a view of the golden-fronted woodpecker's skull and beak from above. The area highlighted in red is the point of impact that receives residual forces from the bird's pecking activity.
Illustration by Allison Miller.
The photo and illustration at right reflect how the structure of this area is comprised of compact and spongy bone.
Photo and illustration taken from Wang et al. under creative commons licensing.
This strategy was contributed by Allison Miller.
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