'The Beating Heart Of The Park's Ecosystems': How Bioacoustics Are Teaching Land Managers About Songbirds In Woodstock
Close your eyes for a second. Listen. What do you hear? Do you notice the hum of a refrigerator? Are cars driving by? Kids yelling and playing?
This is a soundscape. The sonic environment created by — and creating — the place where you are.
“Our soundscape tells us a few things right away,” says Laurel Symes, who studies bioacoustics at Cornell University. Bioacoustics is the science of listening to a natural environment to learn more about how that environment might be changing.
Maybe your soundscape tells you that it’s summer, gives you an idea of the weather and time of day, a sense of where you are.
“If you practice listening to natural sounds, it can tell us at least as much about what's going on there with nature,” says Symes, who’s the assistant director of the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology.
And that’s what researchers started doing at Marsh Billings Rockefeller National Historical Park in Woodstock this year.
In mid-July, Aaron Weed tramped through the forest at the park, heading for one of the 25 trees where researchers mounted acoustic recorders at the end of May.
“Sometimes we've got a little bit of hiking to go through,” he said over his shoulder. “This [one] is not very far at all.”
Weed works for something called the Northeast Temperate Inventory & Monitoring Network, part of the National Parks Service. His job is to keep an eye on the health of the ecosystem at Marsh Billings, looking at things like water quality or animal populations.
A few more yards into the woods, Weed found the tree he was looking for. Tied around the trunk about six feet up was a metal box the size of a big sandwich. And peeking out from the bottom, like a stray piece of lettuce, was a microphone. It was programmed to come on every morning and evening from the end of May to mid-July and record the sounds of the forest — specifically, the birdsongs.
“We're generally trying to get this recorder to hear as many birds as possible,” said Weed.
This was the first time acoustic recorders were used to monitor songbirds long-term at Marsh Billings, and researchers hope it will improve their understanding and stewardship of the ecosystem there.
“The nice thing about acoustics is you can go to it with lots of different questions,” Symes explained. Questions about how an environment is changing, and how species are responding to those changes. For example: As leaves come out in the spring, caterpillars, a major food resource for birds, come out as well. As the climate warms, many tree species are leafing out earlier — and caterpillars are coming out earlier. What people like Symes want to know is: are the birds also arriving earlier? Or is there going to be a problem here?
“The birds are spending the winter someplace far south, and they don't necessarily know what's going on up north,” she said. With acoustic recording, “you can go to it and ask: what is the first date in the year where we detect the song of a particular species?”
This kind of information is especially valuable as climate change, habitat fragmentation, and other factors affect ecosystems around the world.
According to the National Audubon Society, two-thirds of bird species are at risk of extinction from climate change by the end of the century. Research conducted by the Vermont Center for Ecostudies has shown that several bird species in the state, including Canada Warbler, White-throated Sparrow, Great Crested Flycatcher, Chimney Swift, Eastern Phoebe, Eastern Wood Pewee and Tree Swallow have all seen population declines in the last few decades. Researchers have called these declines significant and disturbing.
Aaron Weed says birds are one of the vital signs of forest health. “Like car oil pressure, or your blood pressure,” he said, birdsong is “the beating heart of the park's ecosystems that we're monitoring. And we want to have some information, so we know whether something is changing and if that’s good or bad, and if we can do something about it.”
Annual bird monitoring began at Marsh Billing in the early 2000s. Until this spring, it was done exclusively with something called a point count survey. That’s where a trained birder would go out and stand in a given location for ten minutes and identify all the birds they could hear or see.
This year, they also put up those sandwich-sized recorders. With the help of Jeff Doser, a PhD candidate in Forestry at Michigan State University, researchers have been working to integrate that point-count data with the data collected by those sandwich-sized recorders, combining human observation with acoustic recordings.
Doser and Weed co-authored a study this spring, looking at the decline of the Eastern Wood Pewee. They found that using both collections of data together is more accurate, more efficient and more rich.
Laurel Symes at Cornell has been supporting this work.
“Humans have been listening to the world for as long as there have been humans,” she said, “But this is a way that we can go through really big sections of space and time, and start to pick out patterns that no one individual person standing in one place can pick out by themselves.”
And that’s the task ahead.
After taking down the recorder at Marsh Billings, Aaron Weed brought it into his office. It’s on the third floor of the historic mansion on the property, with walls covered in ornate floral wallpaper. He leaned over his laptop, listening to a recording. “You can hear a Chickadee,” he murmured. "That sounds like a Black-throated Blue [Warbler]. And then there's a Hermit Thrush."
This is more or less what a computer will do, with hundreds of hours of recordings. Researchers at Cornell University and Dartmouth College will then be able to analyze data for bird abundance and population trends. “We’ll have some really exciting results from this, I hope, in the next year or two,” said Weed.
In the meantime, they’ll put the recorders back in the forest next year. If all goes well, they’ll expand the acoustic monitoring program to more parks in the northeast — and all this will inform conservation efforts for a rapidly changing world.