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Biologists: Too soon to know if killing barred owls helps spotted owls

One of the lead researchers acknowledges the “gut-wrenching” dilemma of killing one species to benefit another.
Eric Mortenson

Capital Press

Published on April 18, 2017 6:45AM

Last changed on April 18, 2017 10:40AM

Researcher Zachary Hanna of the Museum of Vertebrate Zoology and California Academy of Sciences collects tissue samples from a barred owl killed in a project to benefit threatened northern spotted owls in the Pacific Northwest.

Courtesy of Ray Bosch, U.S. Fish and Wildlife

Researcher Zachary Hanna of the Museum of Vertebrate Zoology and California Academy of Sciences collects tissue samples from a barred owl killed in a project to benefit threatened northern spotted owls in the Pacific Northwest.

Federal wildlife researchers killed 737 invasive barred owls in 2015-16 in an ongoing experiment to determine if removing them will aid the recovery of Northern spotted owls, the bird whose threatened status was at the center of the Pacific Northwest timber wars.

Spotted owl populations have continued to decline rapidly despite environmental lawsuits, protection under the Endangered Species Act and logging restrictions in the old growth timber habitat they favor. Barred owls, which are larger, more aggressive and feed on a wider variety of prey, have taken over spotted owl territory throughout their range in Oregon, Washington and Northern California.

Scientists with U.S. Fish and Wildlife Services and U.S. Geological Survey, partnering with the Forest Service and Bureau of Land Management, agreed to an experiment: Kill hundreds of barred owls in the Cle Elum area of Washington, the Oregon Coast Range and Klamath-Union-Myrtle areas of Oregon and Hoopa Valley tribal land in Northern California.

In Oregon and Washington, field crews shot 642 barred owls using 12 gauge shotguns and captured one owl alive, turning it over to the Oregon High Desert Museum in Bend. In Northern California, where early research by the late Lowell Diller of Humboldt State University documented that spotted owls reclaimed nesting areas after barred owls were removed, researchers killed 95 of the competitors.

High stakes

Ranchers and farmers in the Pacific Northwest have a stake in Endangered Species Act and wildlife restoration projects undertaken by government agencies. They often referred to the potential rangeland restrictions that might accompany an ESA listing for greater sage grouse as “the spotted owl on steroids.” They’ve also dealt with wolves spreading into the four states and attacking livestock.

Northern spotted owls were listed as threatened under the ESA in 1990, which greatly reduced logging in the Pacific Northwest, especially on federal land. Their continued decline could result in it getting listed as endangered, which might bring even more restrictions on human activities in the woods.

So far, nothing has worked. The Northwest Forest Plan set aside 18.5 million acres of the older forests that spotted owls prefer, “But then the barred owl emerged as a threat capable of sweeping through the entire range of the northern spotted owl,” researcher Diller wrote in a 2013 magazine article.

Barred owls are from the East Coast and appear to have moved west over the decades, following development. They are 15 to 20 percent larger than spotted owls, which Diller called “the human equivalent of a heavyweight going up against a middleweight.”

Working on forest land owned by Green Diamond Resource Co., and with federal permission, Diller and fellow researchers killed dozens of barred owls over five years and documented the return of spotted owls. The work had startling results. Spotted owls “rapidly re-occupied” areas where barred owls were removed, Diller wrote. In one case, a female spotted owl returned to a nesting site seven years after she’d been last seen.

Overall, Diller’s work showed “removal of barred owls in combination with habitat conservation could slow or even reverse population declines at a local scale.”

Researchers don’t know if that success will be repeated.

‘Sophie’s Choice’

“It’s way too early to say,” said Davie Wiens, a raptor ecologist with USGS. Diller’s work was “definitive evidence” that spotted owls’ decline was reversed on Green Diamond Resource land, but conditions elsewhere are much different, Wiens said. The Oregon Coast Range, for example, has a much higher density of barred owls, he said.

Even if it does work, land managers might be required to revisit areas and shoot more barred owls to keep them at bay.

Lingering in the background is whether wildlife biologists should be killing barred owls at all.

“It is gut-wrenching,” said Wiens, the USGS raptor ecologist. “It is for all of us.”

He said barred owls are an apex predator that has “completely taken over” spotted owl habitat. “This experiment is a way to get a handle on that.”

Lowell Diller, who died in March, once called it a “Sophie’s Choice” dilemma.

“Shooting a beautiful raptor that is remarkably adaptable and fit for its new environment seems unpalatable and ethically wrong,” he wrote in Wildlife Professional magazine in 2013. “But the choice to do nothing is also unpalatable, and I believe also ethically wrong.”

If human action such as logging caused major alterations to spotted owl habitat, and development paved the way for barred owls to move west, “Don’t we have a societal responsibility to at least give them a fighting chance to survive?” Diller asked.


The owl removal progress report: http://bit.ly/2nMGOKY

The late Lowell Diller’s 2013 article about the ethical dilemma facing wildlife biologists taking part in the barred owl removal project. http://bit.ly/2pLE4Kh


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