Woodpecker Beak Shock Absorbers


Red-bellied woodpecker (Melanerpes carolinas). Credit: Dick Daniels, http://carolinabirds.org

Male Red-bellied woodpecker (Melanerpes carolinas). Credit: Dick Daniels, carolinabirds.org

Woodpeckers are interesting creatures in that they can repeatedly bash their heads against a tree hundreds of times a minute, decelerating at each impact on the order of 1,000 times the force of gravity and not turning their brains to jelly.

Researchers at Mississippi State University took a closer look at the beak structure of the red-bellied woodpecker (Melanerpes carolinus) to get a better understanding of the shock absorber properties of their beaks to absorb that kind of abuse.

They found woodpecker beaks consist of three shock absorbing layers. The first layer is an outer sheath of scales formed from keratin proteins. The woodpecker had more scales and the scales were more elongated compared to chickens and toucans. More, longer scales increase friction between them, helping dissipate energy from impacts. The scales also slide over each other to allow energy to dissipate by shearing forces. In addition to overlapping, the scales form a wavy pattern, absorbing even more energy. These wavy patterns appear in other hornbill birds, but the woodpecker has a much denser wavy pattern.

The other two layers are bone. The inner layer has a large cavity and mineralized collagen fibers to add overall strength to the structure. The middle layer is porous like foam and serves to connect the two other layers. The foam structure is less porous in the woodpecker beak versus those of chickens, finches or toucans. This focuses the stress and strengthens the beak. The overall structure lends to a system capable of absorbing a lot of shock in short bursts and lasts a lifetime for the bird.

This research was published online May 8, 2014 in the Journal of the Royal Society Interface and will appear in July 2014’s print version.

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