My latest owl sighting, another great gray owl on Highway 6 on March 10; although, all credit for spotting this relatively small guy goes to my sister, Katy, who was up visiting with my mom for the weekend.
In addition to the varying calls of the different species, each individual owl has a uniquely recognizable voice. Researchers have recently started to use sonogram technology to identify different owl individuals, which opens up tons of research possibilities; for example, some researchers are now studying lifespan and length of territory occupancy in barred owl individuals.
Captive male barred owl at the Raptor Center in St. Paul, November 2012
Most owls sing at night, beginning around dusk. It had just gotten dark when Steve and I reached the beginning of the route we were planning to survey. We got out of the car and silently listened for three minutes for the sounds of any owl calls. Hearing none, we got back into the car, drove about 3/4 of a mile, got out and listened for three more minutes. This distance is determined by the fact that the quietest owl calls, those of the Northern saw-whet owls, can only carry 3/4 of a mile in good conditions; conversely, great-horned owl calls can be heard up to three miles away. This was the basic process, and this is what we did for the next four hours. It was certainly tough at times, mind-numbingly repetitive. Also cold. But at least it was a beautifully clear night and I was able to do some star-gazing to compensate for the complete silence of the owls.
Steve was surprised that we didn't hear any owls. The owl calling usually begins around the middle of March and will persist through May. Some owls will continue to sing even as they are incubating eggs, and occasionally even after the chicks have been born. On the other end of the spectrum, boreal owls will cease singing as soon as they find a mate. Steve was particularly hoping to hear some boreal owls during our survey (theoretically, there should be more around than usual because of the irruption); if we had heard one, we would have strapped on some snowshoes and gone searching for its nest, as it might be the only time that owl advertises its location vocally. In fact, Steve was so excited about hearing a boreal owl that we ended up driving more than ten miles down an unplowed road to a location where a resident pair has nested for many years. At one point, we had to shovel his truck out of a snowbank, and still heard nothing to reward our efforts.
Boreal owl seen at the Kohlstedt family bird feeder, early February 2013 (photo: John Kohlstedt)
Despite our coming up empty, I know we'll start hearing owls eventually. Owls are famous for being noisy and persistent. One Swedish great gray owl was recorded for four hours every night, repeating his hooting sequence no less than 310 times. A Western screech owl in Washington was recorded calling for two hours straight every night (at 8 calls a minute, that's 960 calls a night!) Boreal owls in the Western U.S. typically call for 2-3 hours straight, rarely pausing in between. Owl calls are also infectious: it isn't uncommon to hear multiple species calling in the same area. There are even five species in which the male and female are known to sing duets together.
Since Thursday night, I've done a little bit of listening at Wolf Ridge (and also amplifying different calls from my iPod to see if that triggers a response). Still nothing, but I'm hopeful that as the weather warms and spring quickly approaches, it won't be long before I'm listening to the calls of the owls every night.
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