I had the opportunity Friday morning to visit by phone with Dr. James Duncan, manager of biodiversity conservation, Manitoba Wildlife Branch, Winnipeg, author of the book "Owls of the World" (Firefly Press, 2003), and former student of Dr. Robert Nero, an expert on Great Gray Owls. Dr. Duncan spends much of his time studying these birds.
He told me that we are experiencing this owl invasion because of the crash of the meadow vole population in those Canadian areas north of us in which the owls breed. Because that main prey item was scarce this spring and summer, he said, there was virtually no Great Gray Owl breeding activity there this year. His banding activities this year included no juvenile birds. He monitors owls and voles in two locations, one near Winnipeg, the other near Roseau. Voles succeed or fail based on weather conditions. Cold, wet weather is hard on them. Voles were plentiful in 2002 and 2003, so the owls did well in those years. This pattern of feast or famine, he said, occurs every three or four years. The owls are being seen along roadsides because ditches and road edges are good vole habitat: moist and grassy. The best thing that can happen to these owls here this winter is lots of snow. Deep snow cover, he said, is good for voles, so it is good for Great Gray Owls. They have no problem hunting successfully in deep snow. Snow crust usually is not a problem, he said. He said he has watched owls successfully hunt through crusted snow that would support his weight; he weighs 185 pounds. If winter conditions are good for the voles, these owls, he said, will return to their breeding grounds heavier than when they arrived here. He said that he and his research team have radio tracked a number of Great Gray Owls. They will move as much as 800k from their breeding territory as they seek better food supplies. He said Minnesota gets the large number of birds it is experiencing this year because northern Minnesota and northern Wisconsin are the southern edge of the northland peatlands, offering appropriate habitat for the voles, and because birds coming down from the north are funneled in this direction by the expanse of Lake Winnipeg. The birds, he said, should become even more visible as we get deeper into the winter and closer to spring. They will begin then to respond to courtship instincts, becoming more vocal and perhaps even offering courtship displays. Asked about the number of sightings, he said he did not believe that there are more owls involved in this invasion than might have been here in other years. What we have more of, he said, is observers. Jim Williams Wayzata
