Know your owls?  Learn the differences between the spotted and barred owls and listen to their hoots

Wiens is tall, with reddish hair, a deep rumble of a voice and a high tolerance for controversy. Before coming to Oregon, he studied the northern goshawk in Arizona, subject of lawsuits, a denied ESA petition and much bitter wrangling. Because the goshawk was also linked to old growth, he kept track of research on the spotted owl. "Right around the time I finished up, I saw this opportunity, and I just jumped on it," Wiens says.

His base of operations is a field office near Eugene. A barred owl decoy sits on a table, a plastic bag over its head. Another stares down from the top of a bookcase. One wall is covered by a large map of the study area, a checkerboard of private land mostly owned by timber companies and public land overseen by the Bureau of Land Management. Blue dots mark barred owl pairs; red dots denote spotted owl pairs. Blue and red pins indicate owls that are radio-marked with little backpacks with antennae that extend down their tails. Out back in the garage, hundreds of plastic baggies are hung up like laundry out to dry. Each contains a regurgitated owl pellet, packed with vole skulls and flying squirrel bones. The place smells of mice, which are used to draw the owls in.

Spotted owls are trusting and thus easy to radio-tag. "You hold a mouse out, and when they come to get it, you can just reach out to catch their legs," says Wiens. Barred owls are constitutionally cautious, another survival advantage. Researchers catch them by playing a barred owl call, and, when the owl barrels down to attack the intruder, scientists sweep it into a mist net and slip a backpack over its wings. When Wiens demonstrates how he plays a barred owl call through a megaphone, birds near the field site explode. A rooster crows, small birds burst from a nearby tree. A Cooper's hawk wheels overhead, crying, "Kek kek kek."

"Biologists in the field know without a doubt that the barred owls are having an effect on spotted owls. Maybe you don't know the mechanism--did the kill them? Did they drive them out? But it's clear they disappeared." -Lowell Diller, biologist

Surprisingly, some of the blue dots and red dots are very close, indicating that barred owls and spotted owls have set up housekeeping in the same neighborhood. In one case, two nests are little more than 400 yards apart. Wiens puts a finger next to the adjacent pins. "These are the sites we're most interested in," he says. "There's the most potential for interaction."

Early records of spotted owls highlight their similarity to barred owls. When John Xantus de Vesey, a Hungarian exile who took up natural history, reported the first spotted owl at Fort Tejon in California in 1857, he recognized it as a new species but gave it the name "California barred owl."

In 1872, Charles Bendire saw a bird he thought he knew at Whipple's Station, outside of Tucson, Ariz., and shot it. "On picking it up I supposed it to be a common Barred Owl, and only on my return to camp did I realize the prize I had secured," he wrote in his Life Histories of North American Birds. It was the second documented spotted owl. The egg was so similar to that of the barred owl, he     didn't include an illustration.

The birds themselves look alike, but aren't identical. In addition to its larger size, the barred owl has more white on the chest and head and has clear concentric rings around the eyes. The tail has thick bars of brown and white, and its contact call is the distinctive eight-note query. As the names indicate, the barred owl has vertical bars on its chest, while the spotted owl has small flecks all over. The spotted owl is darker with less-visible eye rings. Its contact call is four notes and, when excited, it barks like a dog.

The birds are not that closely related, according to George Barrowclough of the American Museum of Natural History, but they are in the same genus (Strix) and are able to interbreed. In the late '80s and early '90s, giant, ghostly owls appeared in Washington and Oregon. They had yellow-green beaks like spotted owls and tails with strong stripes like barred owls. Their chest feathers were a blend of both; their calls were like neither. Most often, these hybrids are the result of female barred owls pairing with male spotted owls. Some of them can produce young: A male hybrid and a female barred owl hatched two chicks in the Klamath Mountains in 1990. Overall, researchers have documented more than 50 of these mixtures. Even if the barred owls don't out-compete spotted owls, they may be diluting their gene pool.

Researchers tell stories of interactions that look a lot like competition, however. While evidence reported in the published literature is scarce, Lowell Diller, a biologist with Green Diamond Natural Resources, a timber company in Northern California, says the barred owls are definitely interfering with their cousins. "Biologists in the field know without a doubt that the barred owls are having an effect on spotted owls," he says. "Maybe you don't know the mechanism -- did they kill them? Did they drive them out? But it's clear they disappeared."

He adds, "We don't have any evidence that a spotted owl has managed to retain its territory when a barred owl shows up."

Wiens was tracking a pair of spotted owls getting ready to nest when he heard two barred owls nearby. They hooted again, night after night. Then he saw the male barred owl chasing the male spotted owl. "He was definitely fleeing," Wiens says. The male barred owl died and the spotted owls settled back in, but the next year another pair of barred owls showed up. "Within a week the spotted owls were displaced," Wiens recalls. "The spotted owls found a patch of forest -- a very small patch -- and they nested there."

Late one night, Eric Forsman, a spotted owl researcher and one of Wiens' advisors, was trying to tempt a spotted owl close so he could read its leg band. Both man and bird were focused on the bait, a mouse. "This barred owl just came zooming in and knocked it off its perch. Feathers were flying," Forsman says.

Even before he observed these altercations first hand, Forsman tracked the approach of the barred owl with a sense of dread. One night in June 1972, Forsman, then a graduate student, was walking a road by the main fork of McRae Creek in central Oregon, hooting for spotted owls. He heard an eight-note call from a scrap of old growth by a clear-cut. It was a familiar cry, but out of place. "The call continued for several minutes and then stopped. I still don't know if it was a Spotty or a person imitating the Barred Owl, but I suspect it was the former," he jotted in his field journal.

Thirty-six years later, in his office at the Pacific Northwest Forest Experiment Station of the USDA, Forsman reflects that even as he made those notes, he knew barred owls were moving in to the north. In British Columbia, signs had appeared in the 1940s -- telltale hoots at dusk, a feather on a spruce, a carcass by the highway. In the late 1960s, an injured barred owl was nursed back to health and set free in Glacier National Park. Another was shot near Spokane. But Forsman didn't publish his observation, which would have been the first record of the species in Oregon. He didn't let himself consider that it could actually have been a barred owl.

"I just wasn't psychologically ready," he says. "I think for a while some of us were hoping the range expansion would he limited to B.C."

Forsman has been studying spotted owls for decades, through their Endangered Species Act listing, through the Northwest Forest Plan, through protests and litigation. Lanky, with glasses, a brush of gray hair and a quick smile, Forsman looks ready to climb a Douglas fir to inventory owlets at a moment's notice.