Category Archives: Bioacoustic revelry

Wood crackle

The forest is full of strange and expected voices these days…

Here’s one, from a week or so ago. It was a dry day, following two months of record-breaking dry days. The sun was barely down. From the edge of a suburban woodlot, ear-sparkles came from the treetops, like the fizz and pop of a small pine-wood fire or the crackle of water droplets in hot bacon grease.


We walked into the woods with flashlights to find the source of the sound. An intermittent rain of velvety seed pods greeted us, the popped remnants of wisteria fruits. In the dry air they were all dehiscing at once, flicking seeds away from the mother plant in tiny explosive releases.

These are large vines, reaching all the way to the forest canopy. They’ve topped some trees, smothering them. Their vines muscle and squeeze. The seeds are loaded with toxins, so next year will see more colonists tendril-climbing the forest scaffold.


Light, sound, hummingbird wings

From the dawn-light series (see also silk and moth wings)…

There is a moment in the early morning when the sun catpaws through the forest’s tangled blankets, illuminating my hummingbird feeder. The touch is gentle. The claws of midday are withheld. For two or three minutes, sun fires the blur of wings. For the rest of the day, the lights are off and wings move in gray-green, almost invisible.

hummer0hummer1hummer4Unlike other birds that power their flight with only the downstroke of the wing, hummingbirds flip their wings after the downstroke and generate more lift as they pull back their arms. The feather tips therefore scribe a figure-of-eight as the bird crams more gravity-fight into each back-and-forth. They do this fifty or more times every second. Humans can perceive only ten “images” per second and most movies are shot at twenty-four frames per second. To get an acoustic sense of the birds’ frenzy, I slowed a sound recording of the hummingbird in the photograph by one hundred times. The heart-beat thuds are the slowed wings, the strange wind is the sound of insects singing in techno-molasses:

(email subscribers, click on the header link to get to the sound file)


Fireworks echo through cellulose and chitin

I recorded the Sewanee annual firework display at a lookout spot across a mountain cove from the detonations. Before the pyrotechnics, the katydids made my ears ring, but the explosions out-shouted even the combined acoustic power of tens of thousands of singing insects.

Here is the finale of the show:

(email subscribers, here is a link to the sound, or click on the page title to go to the site)

If you listen with earphones, you’ll hear the low-frequency roar of the fireworks rushing down through the mountain cove for five long seconds after the blast. From where I sat at the Proctor’s Hall rock, the echo ran from right to left, flowing down, like a dark bird launching from the cliffs to the fields below the cove.

Thank you to the Sewanee Volunteer Fire Department for their annual extravaganza of sound and light.


High water: Buggytop cave.

Last week brought seemingly never-ending rainstorms to Sewanee. The downstream effects were dramatic. Crow Creek, running from the entrance to Buggytop Cave, south of Sewanee, was overtopping huge boulders and engulfing trees.

2015-07-05 buggytop boulder2015-07-05 buggytop treeThe water here comes from the sinkhole in Lost Cove and from the many streams that run from the south side of Sewanee. The water’s brown tinge is a melange of woodland tannins, soil erosion, and whatever washes from the streets and houses of exurbia.

Inside the cave entrance, the water’s sounds echoed from walls and the low ceiling. Quite a thunder.

(to hear sound, email subscribers need to click on the post’s title to link to the webpage)

The Buggytop cave entrance is a wide maw, easily walkable when the water is low. One hundred or more feet of limestone cliff extend above the entrance. The cave goes back about a mile into the limestone. According to Gerald Smith and Sean Suarez’s ever-fascinating Sewanee Places, the cave gets its name from the folded appearance of the collapsed rocks inside the entrance. Coincidentally, an abandoned buggy trail from Sherwood into Lost Cove passes not far from the cave entrance. Smith and Suarez also relate that the cave’s accessibility and popularity make it the number one site for local cave rescues. Many a poorly-equipped wanderer has become disoriented after their lights fail, both inside the cave and on the sinuous trail from the road. I was not tempted to join the list of rescuees by attempting a solo passage through the whomping water. Sitting in the presence of the echoing tumult was excitement enough.

2015-07-05 buggytop entrance


What does a rattlesnake sound like?


…before being released from the bucket in which I transported the snake from a friend’s house.

One cannot age a rattlesnake by simply counting the rattles (they gain a rattle with each molt, but usually molt more than once per year). However, this one was a youngster, maybe two years old? My post from June 2013 has a look at their teeth and some better scale shots of a larger individual.

2015-07-07 rattlesnake 0112015-07-07 rattlesnake 0082015-07-07 rattlesnake 007May your crawlway be strewn with sunflecks and chipmunks, young snake.

Peepers: freeze protection strategies

When the temperature dropped below forty degrees, the frogs shut up. A few hours later, we hit the twenties, the pond was ice and the rocks from which the frogs had called were snow-covered.

The only sound was the creak of a Virginia pine’s knotty entrails, twisted by the weight of ice on its needles and branches. (Like other sounds on this blog, you’ll need to be on the website not the email summary, to hear.)

How do these crazy little frogs survive such temperature swings? Surely they’re all frozen to death by now?

A thermometer inserted just below the crust of snow and ice suggests the peepers’ first strategy. It is ten degrees warmer just an inch under the soil. By creeping into holes, bark crevices, and cracks in rocks the frogs find microclimates that, if not toasty, are more temperate.

2015-03-05 ice snow 010The peepers’ other defense is not so obvious. Their livers gush glucose into the blood, flooding their organs with sugary antifreeze. The bodies of these candied frogs can freeze without damage to their cells. Peepers can move in and out of this sugar-high within hours, making them well-adapted to the ill temper of the spring weather goddesses in eastern North America. After the last ice age, they were one of the first frog species to hop up north.

(For those wondering after my last post how a “spring pepper” might differ from a spring peeper, see here. Apologies for my many typos…)

Heck yeah: Peepers, peepers.

Rain + warmth = Pseudacris crucifer. The spring peeper.

Spring? Seriously? Appearing for one night only at a backyard pond in Tennessee. Tomorrow: the freeze returns.

2015-03-04 peepers hawkins lane 011

2015-03-04 peepers hawkins lane 007They are calling at an ear-ringing 85+ decibels. These frogs are so loud that birds have to adjust their songs near chorusing peepers. So crank this one to 11:

peeperspectroZoom in on the spectrogram (below) and we can see two call types: short upward sweeps and longer trilling sweeps. The short, untrilled sounds are the males calling to females; the zipped calls are aggressive signals to other males. Zip-a-dee-doo-dah. You can clearly hear each call type on the recording, minus Armstrong’s horn.

peeperspectro2Bonus: how many peppers can you spot in the photo below?

2015-03-04 peepers hawkins lane 001

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


Sandhill Cranes at Hiwassee Wildlife Refuge, TN

2015-01-16 Sandhills 037Tens of thousands of cranes gather at Hiwassee. Gruuu gruuu: sound resonates within the trachea coiled within their sternum. Horn section of the avian band. An ancient sound; Sandhill Cranes have flown across North America for at least ten million years.

In this recording, made on my phone, you’ll hear the cranes overhead, and the ack-ack artillery of photographers shooting their pixel flak skyward:

2015-01-16 Sandhills 028“…not quite the world’s” William Stafford, Watching Sandhill Cranes

“…so stears the prudent Crane/Her annual Voiage, born on Windes;/the Aire
Floats, as they pass, fann’d with unnumber’d plumes…” John Milton, Paradise Lost

“The crane’s legs/have gotten shorter/in the spring rain” Basho (Matsuo Kinsaku)

2015-01-16 Sandhills 022

The dancing oysters of Hiroshima’s market

oystersThese oysters were harvested in the Seto Sea off the coast of Hiroshima. This sea has thousands of bamboo rafts floating on its surface, each raft home to huge colonies of oysters dangling from ropes in the water below. The region produces tens of thousands of tons of oysters every year, a large portion of total Japanese production. There are so many of these oyster farms that the filter-feeding activities of the oysters have a significant cleaning effect on water pollution in the region. Unfortunately, the accumulated toxins mess with the sex lives of the bivalves (an aphrodisiacal irony?) and possibly the health of those who eat them. Fortunately, in the last few decades, wetland restoration efforts have helped to restore vitality to the sea and reduce these problems.

Back to the market: The oysters were not just quietly lying on ice, as oysters so often tend to do. Not only were the oysters decorated with miniature representations of the torii gates at Itsukushima Shrine, these oysters had a funky groove. I took a short video of this zoological son et lumière show.

乾杯, 高貴なカキKanpai, noble oysters!