The invasive barred owl began expanding into Oregon and Northern California during the late 20th century, contributing to the decline of the threatened northern spotted owl.
A new study shows that, in northwest California, barred owls favor the forests that provide some of the best habitat for their native counterparts.
“They prefer what's called spotted owl habitat, and the better the habitat, the more they select for it,” said Vitek Jirinec, a researcher at the Integral Ecology Research Center and the lead author of a new study.
Researchers worked with the federal government during a barred owl removal program to capture some owls and attach GPS trackers to determine their movements across the landscape.
The center has worked with the U.S. Forest Service, the Hoopa Tribe and the California Department of Fish and Wildlife to study barred owls.
Co-founder Greta Wengert said the work looks at what diseases the owls may carry and their exposure to pesticides, among other factors.
“It's a larger program looking at what barred owls are consuming, their diet, and whether that overlaps with other species or is a threat to other species,” said Wengert.
While scientists have known that the barred owl prefers older, more complex forests, this study confirms both owl species like the same type of habitat. And the barred owl wins when they compete with the northern spotted owl.
“They're slightly bigger, they're stronger, they're more aggressive,” Vitek Jirinec said. “They eat everything that the spotted owls do, but then a lot more, and they occur at higher densities, so they will eventually win.”
Barred owls have driven northern spotted owls to functional extinction in the northern part of their range. Another recent study found no signs of northern spotted owls north of Seattle, where barred owls were more common.
Jirinec said the findings show why spotted owls continue to decline despite a slight increase in habitat across federal lands. He said removing barred owls is needed to help spotted owls recover.
“We've kind of missed the boat on doing this cheaply back in the day,” he said. “Now, we're going to face a bigger problem than we would have.”
The researchers also found that barred owls in Northern California occupy an area that’s 28-times larger than they would in their native range. Jirinec said the tracking data can help wildlife managers understand the effectiveness of barred owl removal programs.
Greta Wengert said removing barred owls to help spotted owls is a difficult prospect. But she said the removals offer a chance to study their effects on other wildlife, too.
“It’s not necessarily a wonderful thing to know that a species is being removed to make way for another that is endangered,” she said.
