Deciduous forests are dominated by broadleaf flowering trees located at temperate latitudes and are sometimes referred to as hardwood forests. Deciduous forests are naturally quieter than tropical forests because the Earth’s curvature spreads sunlight (arriving at an angle) over a much larger area than in equatorial or tropical areas. Diminished solar energy translates, accordingly, into a less powerful engine to drive the bioacoustic system.
Deciduous forests are dominated by broadleaf flowering trees located at temperate latitudes and are sometimes referred to as hAs the angle of the arriving solar energy gradually changes with the seasons, the loudness of the natural ambience also gradually changes and we hear great differences in animal activity. The solar equinoxes (generally March 21 and September 21) mark pivotal points in the annual cycle of natural sounds. Spring is a natural boom time and a very active bioacoustic season, particularly for birds, who are counting on an ample supply of food to raise their young. Summer with its warm temperatures, is also a prosperous time of plant growth, and many fast reproducing insects industriously tap this wealth, until colder temperatures usher in the season of silence: winter. We will learn more about this in Sound Designing with Deciduous Forests.
Not only will you hear a quieter ambience than in the tropics and a wider range of faint to loud sounds throughout the seasons, but owing to the reduced species diversity and spacious forest structure, deciduous forests—especially ancient deciduous forests—offer recordists a more spacious performance hall with fewer performers. Thus a pattern emerges; as we travel from more evolved forests towards less evolved forests, the overall ambience becomes quieter and sonic diversity decreases. This is readily apparent in coniferous forests, which are less highly evolved than deciduous forests. I’ll share more recording strategies and tips about spacious, less diverse soundscapes in a future article.
JOYCE KILMER MEMORIAL FOREST
I remember my first visit to an ancient deciduous forest. Although I had assumed I had already recorded an ancient forest, it wasn’t until 1989, when I stood on a crisp spring morning amid towering trunks and beneath spreading branches high overhead in Joyce Kilmer Memorial Forest that I learned otherwise.
This 3,800 acre living cathedral in North Carolina is named after poet Joyce Kilmer who was killed during World War I by a sniper’s bullet. He is best remembered for these two lines:
I think that I shall never see
A poem as lovely as a tree.
The poem continues:
A tree whose hungry mouth is prest,
Against the sweet earth’s flowing breast;
A tree that looks at God all day,
And lifts her leafy arms to pray;
A tree that may in summer wear,
A nest of robins in her hair;
Upon whose bosom snow has lain;
Who intimately lives with rain.
Poems are made by fools like me,
But only God can make a tree.
It is with this reverence for life that you should silently enter nature’s cathedral, and, if you will, worship — the truest form of listening.
I learned this after hearing a twittering song that floated and echoed through that wonderous, leafy place of worship. The songster, a tiny Eastern Winter Wren, taught me a big lesson. At the time, mistakenly believing closer was better, I approached slowly, avoiding eye contact. Even so, the wren wanted no part of me and took wing up a nearby mountain. I scrambled, conspicuously, noisily, after him. I had to have this recording!
I heard him again, singing his heart out, in an Eastern Hemlock near the top of the mountain. Slowly I approached to within ten feet or so. This time, the mere tap of my index finger on the record button was enough to send him aloft—back down the mountain. I gave chase again, working up a sweat crashing through bushes, only to have him fly off once more when I got too close. I felt like a toy on a string, until finally, perhaps he relented, and resumed singing boisterously even with me nearby.
That’s when I discovered I was out of battery power. Knowing that batteries can regain some power when warmed, I unzipped my jacket, poured the frosty batteries onto my hot belly and held them there for a minute or so, before popping them back in my recorder. I got a recording of this Eastern Wren all right, but it sounded harsh, homeless, lost in space without any sense of context. Remembering my position where I first heard this angel, I backed off, maybe 50 to 75 feet, a much less threatening distance for birds, and learned a valuable recording lesson. At this new, more distant perspective, the song, in travelling through the forest, voiced in its home, sounded much sweeter to the human ear.
TIPS
Every nature sound recordist will want to set up inside an ancient deciduous forest in springtime, though doing so is becoming ever harder. It was once said that a squirrel could travel from the Atlantic shore to the Mississippi River without ever touching the ground, but the great ancient Eastern forests of yesterday now remain only as a few small remnants. Encroaching noise pollution further limits pristine recording opportunities. Here are some scouting tips:
Internet homework similar to what’s discussed in the article „How to Record Prairies“ will help you locate extant ancient deciduous forests. You can start with a list of all ancient forests of the world. Then identify which ones are least polluted by man-made noise by overlaying transportation routes. Finally, check potential forests using Google Earth to determine adjacent land uses and possible noise intrusions.
If all suspected sources of noise intrusions are intermittent, then you may well have a window of opportunity between flight schedules or other activities. If you are fortunate enough to have a choice between two locations within a single time zone, opt for the eastern one to give yourself the advantage of an earlier sunrise, when more humans will still be in bed. And remember that nature does not observe a Sunday Sabbath, so there’s generally no better day to record sunrise. Understand that to do so, you will want to arrive at least several days in advance, allowing enough time to audition the performers, select optimal recording positions, and maybe pray the weather cooperates.
A second-growth deciduous forest is nothing like an ancient forest in both appearance and sound. Ancient forest trees must be shade tolerant, exploiting weak and speckled light to grow taller. Their trunks or boles remains straight and relatively unbranching until they reach the forest ceiling or canopy; hence the distinct visual resemblance to cathedrals (widely spaced columns supporting branching, vaulted ceilings) and similar acoustics (reverbe
ration time of two seconds or longer). Second-growth deciduous forests, such as those which occur after logging, have trees which thrive in full light and branch close to the ground. This results in an entirely different look and acoustics. But how compromised by man-made noise is a location likely to be? Let’s check out South America’s population density compared to the rest of the world.
STORIES
Both ancient and advanced second-growth forests are organized into stratified layers or stories—like in a cityscape. The high-rise buildings (the overstory) dominate, catching the direct sunlight. A lower residential complex (the understory) is made up of smaller trees and shrubs often half as tall. At the forest floor we find woody and herbaceous plants (the understory forb layer). There is also the litter layer (the basement of the forest, if you will) which contains more species than the rest of the forest combined–insects, earthworms, nematodes, fungi, and bacteria.
It is important to look at your forest, and get to know it, because each of these growth levels has a different microclimate, ultimately effecting how much sound is produced, the speed it will travel, and how far a sound will travel before it fades (atmospheric attenuation). You can identify these microclimates by studying the phenology as expressed in the condition of leaf and floral buds.
In spring, the warming rays of sunlight at the lowest layers allow for early spring leaves. Fanned by cooling winds, the upperstory will not leaf-out until late spring. As the progression of buds and leaves ripples upwards you will also notice changes in sound.
Leaves reflect and scatter birdsongs and other forest sounds. Out of sight, burbling streams that were inaudible when the forest was leafless may become clearly audible when the upperstory leaves reflect stream sounds downward. As spring turns to summer and the newly emerged leaves mature, they go from being supple and nearly silent to become firm solar panels that rustle. Winds are also much reduced in lower stories than upper stories, meaning that timing your recording session to precede upper story leaf emergence will reduce the audible presence of wind.
PRACTICE
Now let’s pull this all together to compose a soundscape portrait much like we would compose a picture with a camera, except our lens is a microphone. We will now try to find a position within the forest and wait for just the right time to close the shutter or push record. This takes time and of course we could sonically Photoshop our portrait, but why? The audience would feel cheated and what is there to learn? Let’s do this old school.
Imagine yourself standing inside our living cathedral. Tall clean columns with vaulted ceilings completely surround you. Do you imagine leaves present—power on; or leaves absent—power off? There is no right or wrong choice, but this will affect the subsequent choices you make.
Let’s imagine half the leaves are out and green. The uppermost layer is still leafless, but power is on, and more importantly ramping up. Neotropical songbirds have probably already arrived after overwintering farther south and are starting to stake territorial claims. Seeing fresh leaves indicates that songbirds will be singing with bravado, starting just before sunrise and continuing well through the morning, at least until the wind kicks up.
The presence of leaves in the lower layer offers several advantages. The microphone’s visual presence is more easily concealed. (Eyes cannot see behind objects—although ears can.) So as long as you are completely quiet you can position your microphones closer to places you’ve identified as routinely chosen by a particular bird as a song post.
If there are leaves, then there could be flowers. So hunt for a flowering bush. Some flowers attract birds, true, like hummingbirds and their whirrrring, ziiiinging, classic, J-arch mating ritual, but more importantly, the presence of flowers means the soft murmur of insect wings will likely add a sense of depth and refinement to your portrait. Before these insects fly, they will shake the dew from their wings by flapping them fast enough to produce heat for early flight; it’s first come first serve at the nectar bar. This humming sound, a different pitch for each species of winged insect, emerges out of the early morning silence, a sound similar to thousands of faint violins—one of the purest, most sacred sounds of nature, in my opinion, lasting only a few minutes before they take flight, inevitably buzzing by too close to the microphone for the likes of most audiences. Timing is everything.
Best, then, to set-up about eight feet away from the flowing bush to help ensure that an insect doesn’t get too close or annoying. You can also drape camouflage mosquito netting over the microphone from a branch overhead. Tent stakes are not needed to spread the base of the teepee because strong winds will be absent—just use small stones or pieces of wood.
Continue to listen through the microphone throughout the day. Insects may or may not be present. Do you hear any rushing water in the distance? If you do, do you like it? Does it add to the experience or detract from the experience because it will only be louder under the optimum conditions of sound propagation at dawn. Perhaps you’ll need to find a different flowering bush. Is there wind in the tree tops? Notice the roar from the uppermost bare branches and how wisps rarely intrude into the lower layers of the forest. The problem with forest wind is that this waterfall-like sound will drown out echoes. Echoes are as much a part of forest acoustics as the birds themselves. You want them in your recordings, so know that lowering the wind sound will help preserve the echoes as a day advances—and the only way you can control this is by timing your visit before the forest’s uppermost layer has leaves.
If there’s a spring shower, notice how wet leaves reflect sound better than dry leaves, and how everything sounds brighter, fresher. Listen to the pattering of rain, distinctly tapping each leaf , it allows a nice visualization for the audience of the plants close by. The contrast provided by brief drops and long flowing BOOM Library – How To Record Deciduous Forests birdsong may also be stunning, especially when the drops progress to include drips (read more about this in the article „How to Record Thunder and Rain“).
I suggest remaining here at this bush for the rest of the day until well after sunset. Use the time to watch and listen. As long as you don’t move, you’ll appear almost invisible to many creatures. If you sit still, perhaps with your back against a tree, knees bent, you’ll further enhance your camouflage.
Before you get too settled, checked yourself for ticks. Deer ticks can carry Lyme disease. I keep my pant legs tucked inside my socks so that ticks seeking a blood meal crawl up the outside of my pants, making it more likely I will notice them. You can also spray your bulging socks with insect repellent to further deter t
hem. I use 100% Deet in a small spray bottle. Be careful that you do not get this on your hands, lest you transfer it to your equipment. I’ve had insect repellent dissolve plastic on my windscreens and even melt threads on my clothing. Even doused with Deet, you can’t check yourself too often for ticks!
Most forests also have snakes underfoot. These cold-blooded retiles like to warm themselves in the sun or lurk beside small rodent paths for their next meal. If you walk slowly, you’ll give them time to slither out of the way, and you shouldn’t have a problem. But always check with forest management. In some locales, you might be advised to don protective snake chaps.
Get to know this potential recording haven. Watch the light fade and listen to what sounds you hear and where they come from. This is the evening chorus, the counterpart to your intended, dawn chorus sound portrait. To a great extent it will mirror the dawn chorus, the same, orderly sequence of bird species, but in reverse.
POSITION
Now that it’s dark, do you think you can improve on your position? A distance of even a few feet, left or right, up or down, from your current position can be significant. Maybe you’ll want to move 100 feet. Go there, position your microphone stand and tie some white survey flagging onto it. The white flagging will make it easier to spot in the pre-dawn when you crawl out of your sleeping bag and go to clip-in your microphone using a quick-release system to minimize disturbance. I use Sachtler quick releases and Gitzo tripods for dependability and longevity. Now you can turn in for the night, perhaps entertained by a chorus of toads. Toads often live in the forest, removed from ponds or streams, residing in the puddles that accumulate in low places in spring, where they lay eggs after mating. This courtship of calls and loud trills has been my bedtime story many a night. You’ll want to turn in with your recorder and the battery pack beside you inside your sleeping bag to keep the batteries warm and at full power. Your microphones will spend the night outside inside a separate drying bag (read details in How to Record Thunder and Rain). Microphones kept at ambient temperature perform better. When you start recording in the morning, the cool moist air will not condense on the already cool, dry microphone membrane and circuitry. Water conducts electricity as easily as metal, so by avoiding excessive moisture you avoid possible electronic failure, or worse, very low levels of spurious noise that you don’t detect until you return home and listen more carefully…to your ruined work. I often set my cell phone’s alarm clock to vibrate beside my head at least an hour before sunrise. Even with this much cushion, there is little time to lose. As the dome of light on the eastern horizon washes away the stars, I move into position by headlamp, locate the white flagging, clip-in my microphone, and get comfortable—really comfortable. Mark those words. You’ll not be moving more than an eyebrow for possibly as long as two hours.
FIRST MORNING
This is your first morning. Let the learning begin: what makes this location unique and this time of year special?
Engage the recorder and set gain levels. Keep your hand under the flap of the recorder bag with the bag flap closed to keep the LED display from being seen by soon to awaken nearby wildlife. With practice, you will learn to navigate the controls by touch, especially if you have glued a different grit of sandpaper to any buttons likely to be confused with each other. Of course, you do not yet know what is going to happen, and maybe your settings will be a bit off, but you’ll know better tomorrow.
On day one, take a chance. Turn up the headphone volume so you can expand your auditory horizon and scan the perimeter for noise pollution. Even though you did not notice any noise pollution during the evening you probably will now. There may be a low frequency throbbing coming from power plants located up to 20 miles away. The stacks used at coal burning power plants are large flutes pumping out unwanted low frequency noise. This will fade as the temperature warms and the atmospheric layers mix. Notice during the most precious time of listening how different thresholds are reached. The sounds of distant rivers will fade in and out of perception. The sound of distant traffic, especially if on gravel, will come and go, agonizingly slowly. The sound of a pickup driven by a fisherman bound for his sweet spot in nature may take five minutes to fully fade away. If you’ve chosen an especially grand sonic amphitheater, you may be listening to more than 1,000 square miles! On the African veldt this special hour is sometimes called the “hour of the lion,” because it is when the keen senses of this feared predator are made even keener.
The hoot of an owl, seemingly 60 feet away, is probably 300 yards from where you sit. Listen to how the echo travels down the valley… and how, before a minute has lapsed, another owl answers. One by one, birds away from their roost flutter into position and begin to sing. Often with the first utterance different than what follows. The chorus builds and then builds more, becoming, in an ancient deciduous forest, in peak season, on a busy flyway, unbelievably complex. Avoid asking yourself, “What bird is that?” Just take all sounds in with equal importance. Listen to the place, and you’ll notice how the entire chorus resembles one much bigger, unified song. This is the result of resource partitioning, a basic principle of ecology whereby a shared resource (frequency spectrum) is subdivided, enabling a new species to thrive and evolve.
There are many kinds of deciduous forests: ancient or secondary, upland or lowland, high latitude and low latitude. Knowledgeable recordists can use the inherent differences to adjust the volume in their sound portraits. If you want to turn down the volume, then go to a higher latitude or seek a higher elevation. If you want to turn up the volume, then move to a lower elevation or lower latitude. The same holds for complexity, or the number of distinctive performers (different species).
SUMMER
As spring passes into summer you’ll hear a pronounced reduction of birdsong as fledglings, now off the nest, stretch their wings and territorial boundaries deteriorate. Insect populations—crickets, katydids, and cicadas—multiply prolifically, feeding on abundant food sources to build a new crescendo. Insects make a variety of sounds, usually by rubbing or scraping together body parts. With 900 species of crickets, 6,400 species of katydids, and 2,500 species of cicadas, you can imagine that certain forest ambiences have deep and complex insect patterns—particularly at night. Late summer is an excellent time to record nighttime insect choruses because ambient temperatures remain warm long aft
er sunset, allowing the cold blooded insects to continue in full concert as any human activities gradually subside.
AUTUMN
In autumn, leaves fall first from the uppermost forest layers. These old leaves have already exported their resources into the tree for transportation and storage in the roots, so the leaves are particularly stiff, imparting the characteristic crunchy rustle whether stirred by wind or by two or four-legged creatures. The last leaves to fall to the forest floor are those leaves growing closest to the ground.
Most mammals are nocturnal and autumn is breeding time for some species, like deer and elk. Others, like coyotes, wait for late winter or early spring. Surprisingly, because day length in autumn equinox now matches spring equinox, male songbird testosterone production is triggered, but only briefly. What I particularly enjoy in these autumn songs, unlike their spring counterparts, is that those individuals seem to have benefited by the spring practice season and now know their voice. It is the difference between week two and week six on American Idol.
WINTER
Winter is the season of silence, characterized most by the hush of falling snow. When windy, the deciduous forest sounds brittle, as crossed branches creak like haunted houses and ice storms test the strength of the oldest veterans.
It is this time of year that my recording activities pretty much shut down and give way to cataloging the year’s work and making plans for the coming year. Top of mind, as for all recordists, is necessarily how to eke out a living while pursuing a passion for sound.
Stay tuned for more Behind The Scenes material
We want to say THANK YOU for putting your trust in our SFX. Stay tuned for more “Behind The Scenes” specials of our new DECIDUOUS FORESTS library.
If you haven’t already done it, listen to our DECIDUOUS FORESTS audio preview!