Northern spotted owl numbers are declining across the Northwest, and the primary reason is the spread of the barred owl, according to a new analysis published Wednesday.
Federal scientists have been keeping tabs on spotted owls for more than 20 years now.
“We have a lot of data that suggests that they’re in real trouble,” said study co-author Eric Forsman, a retired U.S. Forest Service biologist.
The research looked at the decline of the threatened owls through three lenses: climate change, habitat and barred owls. The impact of climate is inconclusive. Habitat loss proved to be less of a factor than in the past, because there’s been no significant declines in the past 20 years.
“Habitat is very important. We all know that,” Forsman said. “But when barred owls show up it doesn’t seem to make a whole lot of difference how much habitat you have. They’re still causing the population to decline.”
Washington has seen the sharpest decline in spotted owls – between a 55 percent and 77 percent loss. Forsman said the barred owl invasion happened north to south, meaning that they expanded in that state first.
But now, Oregon and California are beginning to catch up.
“Now that barred owls have been here longer, in Oregon and California, we’re beginning to see more rapid declines in those areas as well,” Forsman said.
The one possible exception is a small study area in Northern California where barred owls have been removed since 2009. In this small sample area, the overall spotted owl population still declined, but only by 9 percent. Because of the short time frame, the results should not be considered conclusive.
Still the U.S. Fish and Wildlife Service has expanded the barred owl removal experiment. California’s Hoopa Valley Tribe has removed about 150 barred owls from their reservation since 2013.
This year wildlife officials began removing owls in Oregon’s Coast Range and around Cle Elum, Washington. So far 133 barred owls have been removed in Oregon and 105 in Washington.
Barred owl removal is expected to begin in Klamath County, Oregon, next fall. The most recent study does not reflect the results of any of these experimental removals.
The Fish and Wildlife Service said the recent data will help determine if the spotted owl should be given endangered species status. Officials are studying whether to recommend changing the spotted owl status from “threatened” to “endangered.” That change would make little practical difference in how spotted owls are managed, but it could make it more difficult, for example, to get clearance for logging operations in spotted owl areas.
“We are stuck with barred owls,” Forsman said. “I don’t think it matters what we call spotted owls – whether we call them threatened or endangered – we are facing an incredibly difficult problem in term of how we change what is happening to the spotted owl.”
The Fish and Wildlife Service said its final recommendation on whether to change the Endangered Species Act status of the spotted owl is due out in June, 2017.
The latest spotted owl research by the U.S. Geological Survey Oregon Cooperative Fish and Wildlife Research Unit is published in the Dec. 9 edition of The Condor: Applications in Ornithology.