The Pulse of a Waking Forest

Our morning dawned crisp and blue. In the woods, we knew that the trails would be firmly frozen, the mosquitoes still far from flying, and perhaps the ticks would be hunkered down, too. The novelty of this snowless, chilly spring weather is a perfect match for a hike on the North Country Trail.

As we entered the brushy, deciduous forest and strode down the leaf-littered path, I felt my heart quicken and thud in my chest. After a moment, the sensation reached my ears, too. It wasn’t my heart – it was the drumming of a Ruffed Grouse! I’m always amazed by how much I feel their sound instead of hearing it. In the thick of mating season, their incessant, accelerating beats have even caused a fleeting catch in my breath as they temporarily overpower my own body rhythms.

The grouse drummed again; thumping slowly at first, and then crescendoing into a rapid-fire blur. As his last vibrations dissipated into the still air, another grouse answered from a neighboring territory. The low-frequency sounds are audible from up to a quarter mile away.

Over the years, we’ve employed several explanations of how ruffed grouse create this sound. Because male grouse often display from atop a hollow log, perhaps they created the sound by actually hitting the log with their wings. Or, since they also display on rocks, mounds of soil, or prominent roots, perhaps the sounds comes from the wings striking together behind the birds’ back, like a spruce grouse. Those explanations were discredited in part due to some fuzzy photographs of captive Ruffed Grouse by Professor C.F. Hodge of Clark University in the early 1900s.

H.E. Tuttle spent many days in blinds observing drumming grouse from 1910 to 1918, and published his findings in the American Ornithologists' Union’s journal, “The Auk.” Tuttle examined Hodge’s photos and agreed that the sound did not come from wings beating together. He posed the possibility that rudimentary air sacs contribute to the sound (as in the displays of greater sage-grouse).

One theory he dismissed heartily was that the drumming sounds were produced the same way as grouse’s noisy flight. He described it as “an unsatisfactory explanation of that far-away throbbing challenge which steals on the ear so subtly, like the half heard beating of one’s own heart.”

As in many realms of science, as the technology improved, so did our explanations and accuracy. In the 1920s, Arthur Allen of Cornell University used a new-fangled contraption to shoot motion-picture footage of the grouse. By slowing down the movement, he ruled out every explanation except the one that we currently accept.

On the Cornell Lab of Ornithology’s “All About Birds” website today, you can read the result of their founder’s research: “The male Ruffed Grouse’s signature drumming display doesn’t involve drumming on anything but air. As the bird quickly rotates its wings forward and backward, the air that rushes into the temporary vacuum beneath the wings creates a miniature vacuum, generating a deep, thumping sound wave...”

That thumping sound wave sends “the blood sap pulsing quicker along the veins…” (Tuttle again) not only for humans, but also for the lady grouse. She can probably differentiate between different males, since the number and rate of pulses in each bout of drumming is unique to each individual.

Tuttle noted that if he rustled the leaves in his blind to sound like the dainty footsteps of an approaching female grouse, the male would drum instantly, and also flare his name-sake ruff of neck feathers. Once he’s able to attract a female with this huge output of energy, copulation lasts only a few seconds. The female then wanders off to build a ground nest and raise the chicks completely on her own.

Hiking down the trail, we found many clusters of sawdust-filled grouse droppings. Those piles marked where they had digested tree buds and catkins on sub-zero nights while buried snugly in a snowdrift. In one balsam thicket we heard – but did not see – the whirr of a grouse’s startled explosion into flight. We have to admire their tenacity of these year-round residents, even if we sometimes chuckle at their lack of grace.

Now, as the days lengthen with the promise of spring, we can also appreciate how grouse’s drumming seems to jump-start the pulse of a waking forest.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! We are currently constructing our new exhibit: “Lake Alive!” which will open May 1, 2015.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Photo by Larry Stone