Invasive Species: California Biologists Are Killing Invasive Barred Owls To Help Spotted Owls

The Northern spotted owl, native to the Pacific Northwest, has been declining across its range at a rate of nearly 4 percent per year from 1985 to 2013, according to a study published in December 2015. It was declared endangered in 1990.

Of late, there is a culprit contributing to this decline: the invasive barred owl, a native of the eastern United States. The larger non-natives are competing with spotted owls for food, space and habitat -- and they've been called "bullies" by scientists, who note that in recent years they are pushing the native owl species out of its habitat.

One biologist and contractor with a lumber company is participating in a U.S. Fish and Wildlife Service-sanctioned experiment, to kill barred owls in order to protect the endangered owls.

That biologist is Lowell Diller, who contracts with Green Diamond Resource Co., which manages forest-land in three Northern California counties, according to an AP article.

Barred owls have been pushing out northern spotted owls in upstate California, and are spreading south toward San Francisco.

Diller heard that the California Academy of Sciences' ornithology curator, Jack Dumbacher, had received a permit to gather some barred owl specimens. Diller applied for his own permit.

Beginning in 2009, he designated certain patches of timberland for barred owl removal. In other areas, he left the populations alone. Four years later, he noted that in the areas that lacked barred owls, northern spotted owl numbers are not declining.

Diller's findings will soon be published in the Journal of Wildlife Management and Wildlife Monographs, showing that northern spotted owls bounce back when they don't need to compete for habitat with barred owls.

"It's sort of a no-win situation," Andrea Jones, the National Audubon Society's California director of bird conservation, said in the AP article. "We're not advocating for the killing or against the killing."

Jones says that destruction of old-growth habitat has resulted in the two owl species being pitted against each other.

While Diller said in the article that he doesn't enjoy killing the birds, he tries to focus on saving the native species. The northwestern program director of Defenders of Wildlife, Shawn Cantrell, also feels that the invasive removal should be short-term: "When we mess things up, we have an obligation to fix them," he said in the article.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

-Follow Catherine on Twitter @TreesWhales