Imagine the bumping bass you hear at a stoplight when a teenager behind the wheel wants to share thumping music with the world.
Only this is in the darkness of a remote ridge some 3,200 feet above sea level in the Rogue River-Siskiyou National Forest's upper Applegate River drainage.
These low booms are the calls of a great gray owl coming from an mp3 player placed on the hood of a green U.S. Forest Service pickup truck parked on an old logging road by Scott Bodle, wildlife biologist for the Siskiyou Mountains Ranger District.
"The calls act as a male challenge," Bodle explained. "We are trying to bring out their territorial aggression. We are trying to get them to come in.
"We want to find the nest tree so we can mark it," he added. "But they don't always come in. Sometimes they will just sit up on the hillside and hoot back."
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The survey begins in mid-March with three visits to each site by mid-May and another three by mid-June, a period that covers the owl's breeding season.
One of the world's largest with an average wingspan of around 60 inches, the owl is neither threatened nor endangered. But under the agency's survey and manage regulations, any planned habitat disturbance requires a survey of indicator species like the great gray. An indicator species is one whose presence is an indicator of habitat health.
In the district's upper Applegate Road area, a project is being planned to reduce the threat of catastrophic fires in the wildlands urban interface by thinning vegetation built up after a century of fire suppression.
"Where Forest Service meets private we are going in to try to reduce the risk of wildfire running down into private property," Bodle explained. "As a result, there might be some commercial harvest. There might be some cutting and piling of brush and burning those piles. We might do some broadcast burning. But to do any of that we have to see what kind of effect it might have on certain species.
"We're looking to find and document the great gray owls if they are in the area," he added. "If they are not, that gives us greater flexibility with the prescriptions we will be doing as far as fuels treatment."
At the first site visited this past week, Bodle had found a male and female along with a freshly fledged juvenile last year. It's a likely location because the owls often inhabit forested areas near openings such as a mountain meadow or logged-off area, he said.
The soft, low-pitched "whooo! whooo!" could barely be heard by humans standing in the windy darkness a few yards away. The owls can hear far better than humans, the surveyors explain.
"The great gray owl call is so low you can't get a lot of volume out of it," Craig said of the recording. "It sounds quiet to us because it is very deep and very low."
"A lot of it is outside our spectrum of hearing," Bodle added. "The speakers we have meet the range but if I was to put on music at this volume it would be extremely loud."
In the silent minutes following the recording there is an answering sound from the canopy in the nearby forest. A great gray owl?
"If we're very quiet we can walk down here and get a little closer," Bodle whispered. "He'll probably keep going."
Sure enough, the answers continued in a soft but deep hooting sound as the surveyors walked quietly up the logging road, their flashlights held low to avoid scaring wildlife.
Craig stopped to listen once more, then asked, "What's wrong with this picture?"
"Dang," Bodle said, then explained, "Blue grouse."
To the untested ear, the two sound exactly the same, he noted.
"That was close enough to set the grouse off," Craig said. "The grouse has air sacks which produce that 'whoop, whoop' sound. But you can tell the difference if you listen carefully.
"Blue grouse usually don't call at night — it's dangerous for them because it gives away their position," he added. "Yet when he hears that he can't help himself. He starts calling. The blue grouse would be a pretty tasty meal if the owl happened to spot him sitting on a limb."
Blame it on hormones raging in the early spring, he said.
Craig, president of the Oregon Hunters Association, comes to his love of the outdoors following an Applegate Valley childhood spent hunting, fishing and watching wildlife.
"As a kid, I spent a lot of my free time in the woods," he said, noting he still does, if you count the "thousands" of owl surveys made during the nearly two decades he has worked for the Forest Service.
"Most of the owl species are nesting now," he said as they prepared to move to the next call station. "This makes it a good time to do a survey. During the breeding season, they are very territorial, both toward their own species and other owls and hawks."
"Great gray owls don't feed in the timber like a spotted owl," Bodle said. "Spotted owls are found in old growth with multiple-story canopies. Great gray owls feed out in open meadows and hillsides."
They feed on everything from mice and voles to grouse and even rabbits, he said.
"Occasionally a great gray owl will even take a skunk," he said.
The surveyors move on to the next site, set up the mp3 player and play the call that is music to an owl's ears.
They then stand still, listening to the night. Craig heard a screech owl.
"Even a little pigmy owl will respond to this bird that is 50 times larger than it," he said.
Sure enough, he heard a pigmy owl a few minutes later.
"It was just a single whistle note," he said. "After 20 years of owl surveys, I could just pick that pigmy owl up."
You didn't need to be an expert to hear the next sound, a crash coming from the dark canyon below.
"That was a bear, or Bigfoot," Craig offered, then added with a chuckle, "In the dark, it could be anything we make it."
By the time the night was over, two owl surveyors would walk several miles after coming to a downed tree blocking one road to a call station. They would find no great gray owls but would see three deer, three possums and eight foxes, a skunk and one barn owl during their nocturnal survey.
"With no established great gray owls in the area, finding one is like finding a needle in a haystack," Bodle said. "But if they are really there, we've still got a good chance to find one this year."
All the great gray has to do is answer the call.
