Gettysburg College
ornithology

Ornithologists are using drones to eavesdrop on songbirds

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When conservationists put drones to work in field research, they typically function as flying eyes that gather imagery of the habitat and wildlife below. Now, ornithologists from Gettysburg College in Pennsylvania are using drones as flying ears to monitor songbirds in the Appalachian Mountains.

Results of their drone study were published in the peer-reviewed journal The Auk: Ornithological Advances this week. The study concluded that data gathered by drones was about as effective as data gathered by human experts on the ground in deriving an accurate population estimate of songbirds. The full study, “The feasibility of counting songbirds using unmanned aerial vehicles,” was authored by Gettysburg College environmental studies professor Andy Wilson with two undergraduate students in his lab, Janine Barr and Megan Zagorski. 

A male Cerulean Warbler.

A male Cerulean Warbler.

Wilson said he had the idea to use drones to listen to songbirds when he was studying Cerulean Warblers in the area just a few seasons earlier. “It was a hilly area and we were doing surveys mostly from ridge tops. I knew we got a great sample of that habitat, but we were missing steep slopes to either side of us,” the scientist said.

It’s not just steep hillsides but muddy marshes, icy conditions and man-made obstacles from highways to dams, that can block scientists from all the places they’d like to study wildlife. In ornithology, Wilson said, “Sometimes traversing terrain can disturb the birds and stop them from singing.”

Birds sing to mark their territory and attract mates. Constant singing burns a lot of energy. If a bird senses that its songs won’t be heard, due to noise from human activity especially, they may stop singing to save energy. A lack of birdsongs, as the book Silent Spring by Rachel Carson portrays, can indicate burgeoning environmental problems that can have dire consequences to human life, too.

Wilson’s team tied audio recorders to drones with a fishing line 8 meters long to eavesdrop on birds. The lines were long enough that the microphones wouldn’t pick up noise from the drones themselves. The set up also allowed drones to hover at a reasonable distance from the birds they set out to observe. Rather than flying for miles, the drones hovered to act like a human ornithologist conducting what’s called a point count. In a point count, an observer jots down a note about all the birds they can see and hear from a certain location for a set period of time.

The Gettysburg College researchers used DJI’s Matrice 100 quadcopter drones to conduct their study. Research-grade drones used by the likes of large agricultural businesses would have been nice, Wilson said, but aren’t particularly affordable for academic purposes.

While population estimates derived from drone-recorded birdsongs were generally of the same high quality as estimates made with data gathered by ornithologists on the ground, there were a few exceptions. Unmanned aerial vehicles didn’t pick up lower frequency birdsongs like those of the Mourning Dove. And it was hard to suss out a count of Gray Catbirds, because of the high density of their calls. But audio data from drones worked to count other species typical to the Appalachians.

Wilson tells TechCrunch his lab will continue to explore the feasibility of drones to study bird populations. He is planning new studies to evaluate whether or not, and at what point, drones may effect bird behavior. For example, do birds react to drones flown at 50, 60 or more meters away? And how do they change their behavior, if yes? He also wants to compare the quality of birdsong data gathered by recorders on the ground, to that of drones.

Wilson said environmental scientists generally would like to use drones in their studies, but two things are needed to embrace them more commonly. Even top of the line quadcopters only fly for about 22 minutes in clear conditions per battery, Wilson said. And they’re still loud enough that scientists are concerned about disturbing wildlife. “It’s not just the scientific community that would want this. I think there’s a general market for quieter drones,” he said.

Indeed, nobody wants a whining or roaring robot flying overhead.

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