Pecking with power
Brown University
It’s one
of nature’s mysteries: How can woodpeckers, the smallest of which weigh less
than an ounce, drill permanent holes into massive trees using only their tiny
heads? New research shows that there’s much more at play, anatomically: When a
woodpecker bores into wood, it uses not only its head but its entire body, as
well as its breathing.
Photo by Will Collette
In a study published
in the Journal of Experimental Biology, a team led by biologists at Brown
University reveals how woodpeckers combine breathing and whole-body
coordination to drill into trees with extraordinary force.
“These findings expand our understanding of the links
between respiration, muscle physiology and behavior to perform extreme motor
feats and meet ecological challenges,” said lead author Nicholas Antonson, a
postdoctoral research fellow in ecology, evolution and organismal biology at
Brown.
The team studied downy woodpeckers, the smallest species of
woodpeckers in North America, which populate forested areas throughout the
United States and Canada. Most scientists who investigate woodpecker physiology
focus on neck muscles, said study co-author Matthew Fuxjager, a professor of
ecology, evolution and organismal biology at Brown who has been studying
woodpeckers for over a decade.
Photo by Will Collette
“We’re left to wonder, where does all the power come from?”
Fuxjager said. “Where does the protection come from? Those questions stimulated
our study, which took a more whole-body approach.”
In experiments conducted in Fuxjager’s lab,
the scientists offered woodpecker study subjects some of their favorite
types of wood and then measured the muscles the birds employed while drilling.
The team used high-speed video to observe frame-by-frame, every 4 milliseconds,
how the birds’ head positioning coordinated with activation of various muscles.
They also measured air pressure and airflow in the birds’ airways.
After the woodpeckers were released back into the wilds of Rhode Island, the researchers analyzed the data and made several discoveries. First, they concluded that woodpeckers don’t just use their neck muscles to strike.
“They recruit muscles across the head, neck, hips, abdomen
and tail,” Antonson said, “essentially using their entire body to forge a
coordinated hammer, with the neck stiffening on contact in a similar manner to
how human wrists do when swinging a hammer.”
With each full-body hammer strike, Antonson said that
woodpeckers actively exhale, similar to how professional tennis players grunt
while hitting a powerful backhand.
During rapid tapping, the woodpeckers take “mini-breaths” between strikes. These mini-breaths have previously been described in songbirds during fast trills, Antonson said, but this is the first evidence of a bird using them in non-vocal communication.
The researchers found that the woodpeckers strike with
forces up to 20 to 30 times their body weight, synchronizing each peck with a
breath at rates up to 13 breaths per second.
Photo by Will Collette
Taken together, the results can change how people think
about how woodpeckers, and animals in general, use physical displays to
communicate, Fuxjager said.
“These displays that involve moving the body, either as a
dance, or as a gesture, or even as a vocalization, are a way to convey
information to another individual or group,” Fuxjager said. “In the case of
woodpeckers pecking, they aren’t just doing a simple thing at an extraordinary
speed. They are coordinating all the muscles of their body and their
respiratory system to allow them to perform an impressive feat. More than
speed, it’s a matter of extraordinary skill.”
The same could be said about humans, Antonson added.
“When you’re watching someone perform on American Idol, and
you’re making judgments on whether they’re a good singer or a bad singer,
you’re unconsciously assessing their vocal motor skills, and how they, too, can
coordinate their body movement and their breathing to produce a physical
display.”
The study was supported by the National Science Foundation
(PRFB-2305848, IOS-2423144, DBI-2150328).
