I wake well before dawn – 4:30 am to be precise. It’s an hour that defies logic, unless it is your job to monitor songbirds (as was mine for 15 years). Even though it will be dark for another hour, I hear a robin singing outside my bedroom window (each link takes you to a sound recording). He sounds pleased with himself that his is the first song of the day. I am pleased, too. Their songs remind me why I am willing to get up so early. Robins are always the first to start singing in the morning (and the last to go quiet in the evening). They are indeed early birds, and I’m sure he’s got his worm by now.

I get dressed and check that I have everything I need in my field bag – binoculars, clipboard, pencils, bear spray. Check. I pour strong coffee into my travel mug and head out the door into the inky blackness of the night. It’s only a 15-minute drive to my site – a place called Willow Park along Obsidian Creek in northern Yellowstone. The road there is empty and quiet. No one is awake yet.

By the time I arrive at Willow Park, the rising sun has begun to separate land from sky. This is my favorite part of the morning. I lean against the truck and listen to the dawn chorus – a loud burst of birdsong that lasts only a few minutes before the language of birds becomes more conversational, more like that of humans.

As the sun lays claims to the day, I scan the willows for bears, but the vegetation is so thick that it’s impossible to be sure there isn’t one in there, or more than one. I instinctively clutch the bear spray at my hip, feeling it’s familiar shape. With a deep breath, I push aside thoughts of bears and begin wading through willows that overtop my 5’5” frame.

When I arrive at the first station I pull out my clipboard and begin listening. For the next ten minutes I’ll record all the birds I hear and see before moving on to the next station. Although I carry binoculars, it’s by ear that I identify most birds. At this station there are two yellow warblers, a fox sparrow, three warbling vireos, a common yellowthroat, and a willow flycatcher.

To remember bird songs people translate them into memorable phrases. The yellow warbler’s mnemonic is “Sweet, sweet, sweet. I’m so sweet.” Then a neighboring warbler will reply that he is, in fact, the sweetest. It is in conversation with one another that birds establish their territories, drawing boundaries with sound.

The willow patch is in full sunlight as I arrive at my fourth count of the morning. The traffic along the road has increased – cars, buses, and campers full of expectant tourists drive by. The noise begins to interfere with my counts. I have to concentrate harder to hear the more distant birds. I think how the birds must also have to strain a bit to hear their neighbors.

There is an expectation of quiet in national parks. Quiet is the wrong word: It’s more like an expectation of the absence of human noise. But as more people visit national parks, the natural soundscape is altered by car alarms, cell phones, bus tours, motorcycles, and aircraft. Now national parks and other wilderness areas are struggling with how to deal with noise pollution as visitation increases.

Preserving the natural soundscapes of national parks may not be the most pressing issue the National Park Service (NPS) faces, but natural sounds contribute to our sense of peace and solitude that is often the reason we visit parks in the first place, although we may not know it consciously. But there are also ecological consequences to an increase in human noise.

Birds living near airports have advanced the timing of their dawn chorus so as to minimize overlap with air traffic noise, and in urban areas birds sing at higher frequencies in order to be heard over the morning commute. Many birds avoid singing altogether during rush hour and make up for it by singing more frequently at other times of the day.

A few weeks ago I wrote about how the Natural Sounds and Night Skies Division (NSNSD) of the NPS protects dark night skies, but that is only half of what the NSNSD does. For the last 20 years, the Natural Sounds and Night Skies Division has been collecting baseline acoustical data for national parks all over the country.

The NSNSD gathers information on what kinds of sounds exist in parks, how often they are heard, and how loud they are. They are able to subtract out all human noise to determine what the natural soundscape would be in the absence of human noise. The hope is that those two soundscape maps won’t differ a whole lot, but sometimes they do.

Below is a map of the natural soundscape of the U.S. (the dark blue-green areas are the loudest, while the brown tones are the quietest). Notice how the more vegetated eastern half of the country is naturally louder. The natural sounds are made up of wind rustling leaves, babbling brooks, and the greater abundance of birds and other wildlife that are more abundant in dense vegetation.

Although the NSNSD is still collecting baseline data for many parks, they have discovered that air tours are a major source of noise pollution for some parks. Annually, there are about 200,000 air tours in national parks across the U.S., more than half of which occur in Grand Canyon NP alone. Thankfully, only three air tours were reported for Yellowstone in 2015. But this does not include other types of flying in the park.

I recall my years conducting aerial surveys for nesting bald eagles and ospreys in Yellowstone. Often, there was no other way to access the 30+ nests I monitored since most are located deep in Yellowstone’s backcountry. Although the single-engine supercub airplane I traveled in as a passenger was relatively quiet, I sometimes flew over backcountry campers. I can’t help but think that I had intruded on their sense of solitude and reminded them of the world they had intended to get away from. Although I wasn’t simply taking a tour of the park, it still makes me wonder of the necessity of breaking that solitude in the name of science.

Thankfully, monitoring songbirds is much quieter. In fact, it requires the absence of noise altogether.

It’s 10 am as I finish my last point count. I push my way through the willows back to the truck. The birds have gone quiet now. They are focused on other things like foraging, building nests, and avoiding predators.

Despite the increased visitation and noise, most national parks are still quiet places. The goal of the NSNSD and individual parks is to keep them that way and to improve where they can. Yosemite NP, for instance, has a new fleet of quiet shuttle buses and many parks are installing “No Idling” signs, which improves air quality as much as it does the soundscape. But it’s not a problem that is easily solved. It may require some unpopular policies like a cap on visitation in some parks or requiring visitors to park their cars and take a shuttle bus like in Zion NP.

Providing opportunities to experience natural sounds can have as much impact on park visitors as would viewing a natural scene. The two go together. A natural viewshed would be diminished if the natural soundscape of birds, water, and wind was replaced by the noise of honking car alarms, traffic, and generators.

The ability to identify bird songs is like speaking the secret language of nature. I feel as though I have some special power, though I don’t. Anyone can learn bird songs if they dedicate themselves to it. On the mornings I get to sleep in, I often lie half awake in bed and identify which bird each song belongs to. It’s often the first conscious thought I have. Sometimes I wonder if I’m dreaming.

The earth has its music for those who will listen – George Santayana