Teton Raptor Center developed a low-cost Automated Recording Unit (ARU) to study raptors in the Greater Yellowstone Ecosystem. In 2016, we deployed recorders at eighteen known Great Gray Owl territories to determine territory occupancy and study call patterns, recording 32,391 hours of forest sounds. With the help of a dedicated crew of staff and volunteers, we have analyzed over 2,000 hours of these recordings, and determine that all 18 great Gray Owl territories were occupied in 2016. In addition to recording, TRC field biologists visited each territory four times, played Great Gray Owl calls, and listened for owls to respond. We found that the recordings detected more owls than field biologists playing owl calls. In partnership with Joe Medley, we used Raven Pro software to automatically detect Great Gray Owl calls in our recordings. While the Raven Pro protocol was more time efficient than manually analyzing recordings, the manual analysis correctly identified many more owl calls.
In 2017, we are deploying more recorders to find new Great Gray Owl territories and study other species. We are using Kaleidoscope, a Wildlife Acoustics product, to find and identify raptor vocalizations. Based on where and how often the birds all, we are able to determine whether or not a territory is occupied. We are using this technology to determine occupancy by Great Gray Owls, Boreal Owls, Flammulated Owls, Pygmy Owls, and Northern Goshawks.
Hidden in the hours of wind, rain, ravens, and dog barks, we have found a few prime examples of owl calls. Our recorders give us the opportunity to capture the full forest soundscape, and here are some of our sound clips: