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| Snowy Owl |
By Jim Robbins, The New York Times, May 23, 2011
Charlo, Montana— For 19 years, the owl researcher Denver Holt has journeyed to Barrow, Alaska, each summer to map out the predator-prey relationship between the lemmings that crawl across the tundra and the white owls that hunt them from above.
As he prepares for his 20th field season in the Arctic, he says that the snowy owl has a role to play in understanding ecological changes in one of the fastest changing places in the world. “When lemmings are doing well, everything is doing well — eider ducks, sandhill cranes, arctic fox and weasels,” Mr. Holt said. “If climate change results in habitat changes and it affects the lemmings, it will show up in the snowy owls because 90 percent of their diet is lemmings. The owls are the key to everything else.”
Twenty years of data provides an unusually deep look at a species’ population trends. And more research on snowy owls in other parts of the world — they are found throughout the arctic region — could flag changes in the global arctic ecosystem even without other indicators.
“It’s a believable point,” said John W. Fitzpatrick, director of the Cornell Lab of Ornithology, at Cornell University. “Systems are complex, and if we have an easily accessible barometer for the system beneath it that’s a really good thing, because we can measure cheaply and easily how an ecosystem is doing. It gives us a quick handle.”
There’s an unscientific reason to study the snowy owl as well, Mr. Holt says. They are a charismatic ambassador to the world to warn of problems caused by climate change. The males are often pure white, the females white with mottled gray. And there is something captivating about owls. “People pay attention to owls more than other birds because they look like us,” he said. “They have a symmetrical face, eyes facing forward, a round, flat face and a round head with feathers that look like hair.”
Mr. Holt may know the order strigiformes better than anyone. He has been the director of the nonprofit Owl Research Institute for more than 30 years. “He’s Mr. Owl,” said Dr. Fitzpatrick. “He’s one of the premier owl researchers in the world.”
The institute, with a staff of four, operates in a converted farmhouse at the foot of the snow-draped Mission Mountains near here, on the edge of a national wildlife refuge. Mr. Holt didn’t know it when he moved here from Boston 32 years ago, but there are 15 species of owls in western Montana, 14 of which breed here, more than any other state. Owls, because they are most often active in the dark and low-light conditions, and can’t rely on appearances, also communicate in a complex language. “Hooting, tooting, whistling, hissing and clacking at night — owls are very vocal birds,” Mr. Holt said. “Their mysterious calls at night are why they are associated with witches.”
These attributes are the reason owls show up so frequently in literature, as product mascots, and in popular culture. Harry Potter, for example, travels with Hedwig, a snowy owl.
Owls are also highly evolved hunters and killers. They have the best hearing in the bird world — some owls, like the great gray, can hear a mouse moving under a foot of snow or more and swoop down and capture it without ever seeing it. In owls with a facial disc, the ears are hidden behind it, and are asymmetrical — one is higher than the other. That allows the birds to locate prey both horizontally and vertically for more accurate detection. The round face functions as a kind of satellite dish, funneling the sound to the ears, so the owl can make in-flight course corrections based solely on sound.
Their exquisite hearing does not mean that their powers of sight are diminished. Owls have many more rods in their eyes than humans, which bring in much more light, akin to natural night-vision goggles. Like humans, owls have binocular vision, which means they see in three dimensions. They can also rotate their heads 270 degrees. “In two turns,” Mr. Holt said, “they can see all around them.”
Their wings stand out as a marvel of evolutionary engineering. There is a comblike serrated feather on the leading edge of the wing, velourlike feathers on top and a trailing edge of feathers on the rear of the wing. “These three things combine to reduce aerodynamic flight noise,” so they can surprise their prey, Mr. Holt said. Being rigged for silent flying means they can also hear their prey better.
The owl also has the lowest wing-loading ratio of any bird, which means the wings are much larger than its body mass and provide a great deal of loft. “That gives them great aerial agility,” Mr. Holt said. “They can fly really slow, just above stalling speed. It also gives them the ability to gain lift easily with prey.”
There are about 250 species of owl worldwide, on every continent except Antarctica. They range from the two-ounce elf owl, found in the American Southwest, to Blakiston’s fish owl, a Japanese bird that weights up to 10 pounds. Owls in the tropics eat mostly insects, while temperate owls eat mostly small mammals. “We don’t know a heck of a lot about most species,” Mr. Holt said, in a rapid-fire Boston accent.
That means if they are in trouble, no one knows. The short-eared owl, a ground-nesting bird which has been thoroughly researched, has shown a 70 percent decline in recent years.
Owl researchers are a rare breed because most of the birds are active at night and fieldwork is grueling. Two researchers at the lab, Jessica Larson and Matt Larson, are currently staying up all night to call and net flammulated and saw-whet owls to study their migration.
Though most hunt at night, owls can be coaxed out during the day for research. On a recent spring morning Mr. Holt and two other biologists hiked up a ravine and strung up a mist net, similar to a volleyball net, though with much finer mesh. They headed for a magpie nest that had been appropriated by a pair of long-eared owls, because of voles that live on the grassland around it.
In flashes of gold, brown and white, three owls flushed. Then, seeking to stay beneath cover, they zoomed through a narrow natural tunnel in the tangle of hawthorn and chokecherry trees, until they hit the net and were stopped cold. The biologists ran toward the docile birds, now suspended in the mist net, and carefully unwrapped each to weigh, band and measure it. As the birds were held and studied, they sat quietly with their yellow eyes wide, looking curiously at the captors. They made occasional clicking sounds with their beaks.
“We’re harassing them, but we try to minimize it,” Mr. Holt said, “so we can learn about their behavior.” A study Mr. Holt published concluded that flushing isn’t stressful to the birds, though their stress hormones shoot up during banding and blood drawing. The birds recover quickly though, he said, and don’t abandon the nest.
Mr. Holt has been trapping long-eared owls for 25 years, year round. The population of these small birds, between half a pound and a pound, has been shrinking, though their decline is not nearly as steep as that of the short-eared owl.
The length of the study has given researchers a detailed portrait of the long-eared owl, which only looks like it has long ears — they are actually feather tufts. At three weeks of age the owlets do something called branching. They crawl from the nest out on a branch, long before they can fly. Sometimes they tumble to the ground, but are still fed by the parents. Eventually, using their beaks, feet and wing-pumping, they climb back up.
Long-term studies are rare, Dr. Fitzpatrick said, but valuable. “Long-term studies allow us to understand how organisms deal with variations in nature through time,” he said. “One extreme year in 10 can drive the system, and so long-term data gives us context. But it takes a lot of patience and endurance to keep a study going that long.”
Mr. Holt says the rigors of owl research are catching up with him. “I’ll tell you, I’m 55, and hiking 10 to 15 miles on the tundra, I feel it,” Mr. Holt said, as he trudged out of the ravine where he had captured the long eared-owls, with a backpack full of equipment. “But I can still climb trees better than most students.”
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