SUMMER 2006/VOLUME 20, NUMBER 3
The New "Who's Hoo" of Owl Sounds
Audio guide explores diversity of species, vocalizations
Great Horned Owls don't just hoot. They also squawk, chitter, bark and wac-wac. Those who have listened to screech-owls may not realize that in addition to their bouncing trill, they also make chuckle rattle sounds when annoyed. A male Boreal Owl sings a staccato song reminiscent of the winnowing of a Wilson's Snipe, but when he delivers food to his nestlings, he utters a moo-a call.
Voices of North American Owls, a two-CD audio guide released by the Cornell Lab of Ornithology, provides an unprecedented listen into the world of these nighttime denizens.
The comprehensive guide to vocalizations includes nearly 200 tracks from the 19 species that occur regularly in North America and two rarities (Mottled Owl and Stygian Owl), which have only been recorded a few times. Owls have highly variable sounds from species to species and from vocalization to vocalization. They use calls to proclaim and defend territories, attract and bond with mates, beg for food, express alarm, and warn of aggression.
Greg Budney, co-producer of the audio guide and audio curator of the Macaulay Library, said for years one of the most popular requests of the library has been for owl vocalizations. The library, he said, steadily relied on volunteers to collect owl recordings.
The audio guide features recordings of 58 contributors. In addition to selecting sounds from the Macaulay Library's archives, producer Gerrit Vyn contacted recordists to acquire new sounds and worked with scientists who specialize in each individual species.
Some of the vocalizations were recorded for scientific research, such as the five Ferruginous Pygmy-Owl recordings from Glen Proudfoot, a Vassar College biologist. In some cases, obtaining recordings turned out to be adventures in themselves. Greg Clark, who works with Wild at Heart in Arizona, recalled, "My Whiskered Screech-Owl recordings were done in a snowstorm, with no light, up a steep incline. I felt like I was going to fall down any second."
Vyn, who is also an owl recordist, said he tried to include as much variety as possible, but he also wanted to represent calls that are similar between species. For example, he said, almost all owls make a chitter sound when they are in close contact with others, interacting with people or uncomfortable.
"And some tracks are just cool to listen to," he added.
Among the hoots, shrieks, barks, moans, trills, chuckles and whines, Vyn included Barred Owl sounds that he and colleague Ben Clock recorded during the Ivory-billed Woodpecker search in Arkansas.
"We got vocalizations no one had heard before, such as a bark-like call by a female defending her nest," he said.
Vyn said the CD also includes sounds that people hear at night but that they may not have realized were uttered by owls.
"Almost all the other recordings available to the public are primary songs, like the hoot of the Great Horned Owl or the toot of the northern saw-whet," he said. "People just don't realize owls make so many different sounds or don't recognize what they're hearing." Vyn said the CD is a resource to help them find out more.
Budney said he hopes that biologists and researchers will use the CD as a tool to study the birds and will realize the potential for further investigation. "Because owls are nocturnal, their voices are important to researchers trying to locate and understand them," Budney said. "Despite the superb research, a good deal is still unknown."
Elizabeth Quill is an intern in science writing.
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