To reconnect with nature on Earth Day, I sit on my front porch, eyes closed: listening, feeling, sensing. With my vision temporarily halted, I focus on the cacophony of bird songs. While struggling to identify each bird species without sight, I finally identify the cooing-hoot of the morning dove reminding me of its nighttime sound equivalent of the owl. I ponder the pigeon-like dove that does not appear to be flight-worthy given its portly structure. Its reluctant, sloth-like behavior will wait until the last second to fly toward safety as cars approach.
Next, the tattering of a woodpecker intervenes the sound stage like a tambourine in the midst of a flute concert. What tasty treats is he finding in the bark of that tree? In past years, I have been awakened to an early morning drumming by this woodpecker rapidly pecking at my metal fireplace cap. I run outside in my pajamas waving my arms to shoo away this disoriented bird from my rooftop.
How does the woodpecker prevent brain damage despite its repeated chiseling at hard surfaces?
Here are four stages in which the woodpecker has uniquely evolved to protect its brain:
Stage 1: An elastic, two-stage upper and lower beak in which a softer material precedes the more structural area of the beak.
Stage 2: The lower beak transmits the vibration down toward the neck and body, avoiding the skull.
Stage 2b: The upper beak transmits the vibration to a unique sponge-like bone structure between the upper beak and skull, acting as an absorption layer.
Stage 3: A minimal amount of cerebral fluid reduces the transfer of vibration.
Stage 4: An interesting musculartendis structure called the hyoid starting at the upper beak nostrils, extends over and behind the skull, splitting into two strands around the neck and attaching to the tongue of the woodpecker. As the tongue extends into the chiseled hole looking for food, the hyoid tightens, providing a cradle for the skull and an additional vibration path of the upper beak to avoid the skull.
The woodpecker’s unique shock mitigation process is being used for developing biomimicry-based shock absorber systems.
Woodpecker photo courtesy of www.kmaellis.com
1. Oda, Juhachi; Sakamoto, Jiro; Sakano, Kenichi. 2006. Mechanical evaluation of the skeletal structure and tissue of the woodpecker and its shock absorbing system. JSME International Journal Series A-Solid Mechanics and Material Engineering. Volume: 49 Issue: 3 (July, 2006) Pages: 390-396
2. Yoon, Sang-Hee SH (2011). "A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems.". Bioinspiration & biomimetics (1748-3182), 6 (1), p. 016003.