Adam Spencer, The Triplicate

Federal wildlife officials could start having barred owls killed to protect northern spotted owls threatened with extinction on the Hoopa Valley Indian Reservation as soon as this fall, but the practice has already been in place in Del Norte and Humboldt counties for years on private timber lands.

The U.S. Fish and Wildlife Service on Tuesday released a final environmental review of an experiment to see if killing barred owls will allow northern spotted owls to reclaim territory they've been driven out of over the past half-century.

The technique has proven effective through a study conducted by Green Diamond Resource Company, which owns almost 400,000 acres of timber lands in Del Norte and Humboldt counties. In a joint study with the California Academy of Sciences and the U.S. Fish and Wildlife Service, Green Diamond has been killing roughly 20 barred owls a year since 2009.

In Del Norte, the experiment has been done on Green Diamond lands in the Wilson Creek drainage and the Hunter Creek and Terwer Creek watersheds, tributaries of the lower Klamath River.

Eighty barred owls have been removed so far, Green Diamond officials said, and the timber company has plans to incorporate barred owl removal into a guiding environmental document (Habitat Conservation Plan) that is expected to be complete in 2014.

"Assuming the necessary permits are obtained, removal of barred owls will be expanded to all of Green Diamond's spotted owl study area (most of the ownership excluding isolated peripheral areas)," said Lowell Diller, the leading Green Diamond biologist for the study, in an email to the Triplicate.

A scholary article on the study is expected to be published this fall in the Wildlife Society Bulletin and a full analysis will be completed, but initial results look promising for recovery of spotted owls.

"It is apparent that spotted owls have been rapidly recolonizing areas from which they were previously displaced by the invasive barred owl, so it looks encouraging that barred owl removal will allow for the recovery of spotted owl populations," Diller said.

Green Diamond's barred owl removal study is the first and only U.S.-based example using the kill-one-owl-to-save-another technique.

In addition to the Green Diamond study, two of the sites considered for the federal barred owl removal study are near Del Norte County, including the Hoopa Valley Indian Reservation, which isexpected to be the first site for owl shooting starting as early as this fall. The other site near Del Norte is on the other side of the High Siskiyou Mountains crest, east of Happy Camp.

The agency has been evaluating the idea since 2009, gathering public comment and consulting ethicists, focus groups and scientific studies. It will issue a final decision on the plan in a month.

The agency's preferred course of action calls for killing 3,603 barred owls in four study areas in Oregon, Washington and Northern California over the next four years. The experiment requires a special permit under the Migratory Bird Treaty Act, which prohibits killing nongame birds.

An Arcata-based environmental organization said that although many scientists attempting to recover spotted owls might agree on killing barred owls - the No. 2 threat to spotted owls - "the primary threat of spotted owls, loss of habitat, is alive and well," said Andrew Orahoske, conservation director for the Environmental Protection Information Center. "The extensive logging of spotted owl habitat that continues is not consistent with the overall goal of recovering the species."

"Locally Green Diamond continues to propose timber harvest plans that would directly take out active spotted owl sites, with the most recent example being a timber harvest plan on the Mad River, called 'Nacho Libre,'" Orahoske said.

After EPIC filed a notice of violation under the Endangered Species Act, Green Diamond withdrew that timber harvest plan, Orahoske said. He added that the California Fish and Game Commission will hold a hearing on Aug. 7 for the listing of Northern Spotted Owl under the California Endangered Species Act.

The northern spotted owl is an icon of bitter disputes between the timber industry and environmentalists over the use of forests in the Pacific Northwest. Because of their dwindling numbers, the little bird was listed as a threatened species in 1990, which resulted in logging cutbacks and lawsuits.

Barred owls are bigger, more aggressive and less picky about food. They started working their way across the Great Plains in the early 1900s, and by 1959 were in British Columbia. Barred owls now cover all the spotted owl's range, in some places outnumbering them as much as 5-to-1.

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The Associated Press contributed to this report.