Dead wood and the woodpecker’s g-force

About fifteen years ago, the local electrical company hired a crew of subcontractors to cut and trim any trees that were deemed a threat to powerlines. The crew gave the sugar maple in our front garden a lop-sided haircut, slicing away all the branches on the south side. Regrettably, the equipment they used must have carried spores from a diseased tree: fungus swarmed over the cut branches, then killed the whole maple.

The dead tree stood next to the house, so its upper trunks had to be cut down. We left the lower ten feet standing, though. This part, even if it fell, presented no danger to the house. Ever since, the stump has gradually rotted away, occasionally calving chunks of bark, but mostly turning slowly, slowly to punk and duff.

The birds love to perch atop the tall stump, as have two generations of housecats. Woodpeckers also include the rotting maple on their rounds and this week a pileated woodpecker made a stop. I poked a microphone out of the cat-flap and recorded the bird’s hammering and the powerful sound of its thirty inch wingspan as it took flight.

As you listen, imagine the slamming impact of beak on wood. Human brains are concussed by forces ten times weaker than those that pileated woodpeckers experience. They’d make a fine mascot for a football team. The woodpeckers’ heads attain speeds of 6-7 meters per second before impact, they then hit the trunk and decelerate at 13,000 meters/second^2 or 1000 g (see Wikipedia for interesting comparative examples of “g”).  The birds tolerate this pounding because their multi-million dollar contracts specify that they must. And because they are protected by the angle of beak to brain, the shock-absorbing design of the skull, the tightness of the brain in its case, and the elasticity of muscles.

The spectrogram gives a visualization of the sound, with time moving left to right, and frequency (pitch) shown on the vertical: woodpeckerfull

These two clips show short segments, one from the beginning and one from the end of the recording:knockknock

wingbeats

7 thoughts on “Dead wood and the woodpecker’s g-force

  1. James

    I live on a heavily wooded ridge area above the Delaware in western New Jersey. We seem to have a large population of pileated woodpeckers, judging from the sounds I hear and the many large, squarish holes in our trees. Thanks for the close-up sound portrait and the lesson in woodpecker head and beak design.

    Reply
    1. David George Haskell Post author

      You’re fortunate to have so many close to where you live. Their favorite foods are ants and beetles from fallen trees, so the amount of dead wood on the ground is often the best predictor of their abundance.

      Reply
  2. paddywoodworth

    Woodpeckers are a little like unicorns to us Irish, it seems unbelievable that they exist at all, because we lost our only species about 400 years ago. I could not believe it when I found that I could see five species without dismounting from my morning bike ride in Iowa City. And what’s bizarre is that a Downy sounds louder than a Pileated to my untrained ear. Thanks for bringing back the memories with your wonderful soundscape. Oh, and don’t feel too sorry for us, the great spotted woodpecker returned to Ireland spontaneously a decade ago, and chose the ancient (and restored) oak woods of my native Wicklow to start breeding exponentially. Some things do get better…

    Reply
  3. Scott

    When a Virginia pine (planted [outside its range] in our front yard by a previous owner decades ago) died, we had the tree company lop off most of the branches but left the trunk standing for woodpeckers and perching hawks. At first, the birds ignored the tree (which friends call our “totem pole”). But as the tree has slowly turned to “punk and duff” (wonderful phrasing), the woodpeckers (Downy, Hairy, Pileated, and Flickers) have had a field day.

    Reply

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