The spotted owl has a new enemy

  • Barred owl

    Copyright 1997, Wendy Shattil/Bob Rozinski
 

Last May, a birdwatcher in California's Redwood National Park found the partially eaten body of a spotted owl lying in the trail. Nearby he saw the killer - an agitated barred owl, the feathers of its victim still clinging to its talons.

Barred owls and spotted owls are cousins, both woodland owls, with large, dark eyes and feathers that blend perfectly with tree bark; even their calls are similar.

But until recently, the two species never met. The northern spotted owl prefers the conifer forests of the Pacific Northwest; the barred owl flew the forests of the East.

In the past century, barred owls crossed the Great Plains and moved into western Canada. From there, they spread south into the Idaho Rockies and western Washington, Oregon and California, the shrinking territory of the northern spotted owl.

By the second half of this century, logging of old-growth forests had pushed the spotted owl toward extinction. Now, the tough and adaptable barred owl has made things worse. Barred owls compete against, occasionally mate with and prey upon their threatened cousins, and some biologists believe their presence could spell doom for the spotted owl.

Is the enemy us?

Rocky Gutierrez, a professor at Humboldt State University in Arcata, Calif., who has studied the spotted owl for more than a decade, believes the barred owl invasion is the result of human meddling. When Euro-American settlers came to the Great Plains, they suppressed natural fires and planted trees where there was once an ocean of grass impassable to the owl. The result was a patchwork of small woodlands thick enough, says Gutierrez, to allow the barred owl to hopscotch across the continent.

Barred owls were first documented in the West in 1912 in Alberta, Canada. The birds reached British Columbia by 1943, and were common there by 1966. Because barred owls can nest in young and fragmented forests, the logging that has hurt the spotted owl permits barred owls to thrive.

Barred owls can also use the same kind of nesting sites in older forests that spotted owls need. In southwestern British Columbia, larger barred owls have taken over many spotted owl nesting territories.

Gutierrez describes encounters he's seen between the two species in Northern California. "The owls hoot in each other's face, and barred owls are much more aggressive about this," he says. "In one case that I saw, the spotted owls moved down the canyon with the barred owls in pursuit."

Barred owls have also mated with spotted owls, and some of the hybrid offspring seem to be doing well.

"My educated guess is that the barred owl will have a dramatic effect on the spotted owl," says Eric Forsman, a biologist with the U.S. Forest Service laboratory in Corvallis, Ore. "It won't necessarily result in extinction, but will dilute the gene pool and cause population reductions." Twenty years ago, Forsman's research on the northern spotted owl alerted conservationists to the bird's plight, and helped lead to the owl's protection as a threatened species. Since then, Forsman has helped document the spread of the barred owl into the Northwest.

Forsman says Gutierrez is premature in pegging people as the cause of the invasion. "It's not at all clear that this is some big, unnatural thing caused by humans," he says. "Range expansion could be occurring for reasons we don't understand at all, like minor changes in climate or random chance." It's also possible, Forsman points out, that the barred and the spotted owl were once a single species, and that we are now witnessing the rejoining of two populations long separated by geography.

Regardless, Gutierrez says, the presence of the barred owl in the Northwest only makes protecting old-growth forests more urgent. "If enough large blocks of habitat are available, there should be time for the spotted owl to develop ways to cope with barred owls," says Gutierrez. "If there's no habitat, it's a moot point."

The writer lives in Arcata, California.

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