Barred owl inroad, hybrids complicate spotted owl review

LOWELL, Ore. – It hoots kind of like a northern spotted owl and looks kind of like a northern spotted owl.

And like a spotted owl, it swoops in to take a mouse offered on a stick by U.S. Forest Service scientist Eric Forsman in a rainy stand of old-growth Douglas fir on the Willamette National Forest.

However, this is a hybrid – a cross between a northern spotted owl and a barred owl – and it is one of the wrinkles in the future of the bird that triggered sharp logging cutbacks in the Northwest in 1994 through the Northwest Forest Plan.

The invasion of the barred owl into spotted owl territory over the past 30 years has become the top issue in the review of Endangered Species Act protection for the northern spotted owl, granted in 1990 largely due to loss of its old growth forest habitat to logging.

A panel of experts will report Tuesday in Portland on new information gathered for the U.S. Fish and Wildlife Service, which must make a decision by Nov. 15 on whether to maintain threatened species listing for the spotted owl.

The latest studies show spotted owls are still declining, though just why remains a big question. Loss of old growth forest habitat has been minimal, particularly on federal lands where logging is restricted by the Northwest Forest Plan. Meanwhile, the barred owl is pushing spotted owls out of the way when it moves in.

“Clearly the barred owl is having more of an impact on the spotted owl than any of us anticipated 10 years ago,” said Jerry Franklin, a University of Washington forest ecology professor serving on the panel. “The question now has to do with how much that impact is going to be. Is the barred owl essentially going to drive the northern spotted owl out of part of its range?”

The timber industry, which called for the review, argues that if barred owls push spotted owls out of old growth forests, those stands no longer have to be left standing as habitat unless someone is willing to start killing barred owls.

“It seems like the original basis for listing is really in question at this point,” said Ross Mickey, western Oregon manager for the American Forest Resource Council.

Conservationists counter that protecting old growth forests may be more important than ever with the invasion of the barred owl.

“The barred owl was around at the time of the listing,” said Susan Ash, conservation director for the Audubon Society of Portland. “It’s reached the radar screen to the point that, yes, it’s a new threat. The numbers are high.

“But nobody has an explanation for why they have come into the area. And nobody can prove they are actually causing an impact to owl numbers in the long term. This may be some natural process where two species figure out their own roles in the ecosystem.”

Barred owls began moving west from forests in eastern Canada and Minnesota in the early 1900s. After reaching southwestern British Columbia, they moved south, appearing in spotted owl territory in Washington in 1973 and Oregon in 1978, according to a paper by Forsman and Oregon State University graduate student Elizabeth Kelly. They now reach into northern California.

Rocky Gutierrez, a professor of wildlife ecology at the University of Minnesota, thinks the barred owl may have followed the growth of new forests along rivers as settlers started putting out prairie fires.

Barred owls are bigger and more aggressive than spotted owls, and there is evidence they sometimes kill their smaller cousins. Barred owls nest in the same kinds of places, cavities in large trees, and eat the same kinds of things, small rodents like flying squirrels and woodrats, but are less picky.

There is no good overall population estimate on barred owls or spotted owls, but when the two come together, the smaller and meeker spotted owl generally loses, though not always, Forsman said.

“In a lot of study areas in Oregon, even though we are seeing gradually increasing numbers of barred owls, the spotted owl population seems to be holding relatively stable or only declining slightly,” Forsman said. “So it’s still up in the air what this is going to mean long term.”

Being shyer than the spotted owl makes barred owls much harder to study. Spotted owls answer when they are called, and they accept gifts of mice, which they carry back to the nest to feed their young. When a barred owl is offered a mouse, it just flies away.

Cross breeding remains rare – only 47 hybrids have been confirmed in the wild, mostly in Oregon – probably due to behavioral differences between the two.

“It probably occurs in most cases in a situation where there’s a dearth of potential mates for the barred owl,” Forsman said. “But that we don’t understand very well.”

So far, all the hybrids identified have been the product of a male spotted owl and a female barred owl. That may be because it’s easier to find male spotted owls, which will accept a mouse from a researcher and take it back to the nest. Hybrids breeding with barred owls seem to produce more young than hybrids breeding with spotted owls.

To an expert eye, hybrids look like a cross between the two. The facial discs are larger than the spotted owl’s. The back of the neck is streaked with white. The lower abdomen is streaked with brown. The hoot is a mix, too.

The Fall Creek drainage on the Willamette National Forest is a hotbed of hybridization. Six hybrid sites have been identified, while other study areas have few or none.

“The interesting thing for me is we are seeing, if anything, more hybrids down here in Oregon than they have up north (in Washington), where the barred owl showed up earliest,” Forsman said. “The barred owl has been in British Columbia earlier than down here, yet we’ve never seen a case of hybridization up there.

“If hybridization becomes fairly common … it’s going to become very complex,” Forsman said.