Proposed strategy seeks to eliminate invasive owls
Perched high near Bolinas Lagoon earlier this month, a barred owl slowly swiveled its head, surveying its new home with sleepy disregard.
Then it vanished — taking with it all hopes of capture.
The owl's escape underscores the challenge of preventing a surge of these invasive birds, which are expanding their range into the northern San Francisco Bay Area from the Pacific Northwest, threatening the nation's richest population of native endangered northern spotted owls.
Wildlife officials have shot 11 barred owls in Marin County over the past three years, helping to control the species' spread. Yet the arrivals continue.
To expand efforts, the U.S. Fish and Wildlife is proposing a new management strategy, easing the onerous permit process that's currently required to kill the birds, which are protected under the Migratory Bird Treaty Act. The plan, which is likely to be controversial, will open for public comment within the next several months.
“Without some sort of management intervention, spotted owl populations are going to go extinct,” said Bill Merkle, wildlife ecologist with the National Park Service's Golden Gate National Recreation Area. Studies show that barred owls outcompete spotted owls for food and nesting sites, and removing barred owls helps stop the endangered owls' decline, he said.
“We need to hold the line because it's much harder once barred owls are established,” he said. “We need to push them back in a strategic way. This plan will provide that framework.”
Currently, a research permit is needed to get rid of the birds, said wildlife ecologist Dave Press of Point Reyes National Seashore, where spotted owls continue to flourish. That's a rigorous requirement. Under the new USFW proposal, land managers could eliminate barred owls as part of a general management plan to protect the more perilous species.
Advocacy groups such as Friends of the Animals have protested the killings, saying it is a morally unacceptable approach to ecosystem management.
Wildlife officials say they do not enjoy killing owls. But they say it's needed to protect the spotted owl. Outside of Marin County, populations are spiraling downward.
Once abundant throughout the ancient coastal forests of the Western U.S., the spotted owl gained fame during the so-called Timber Wars of the 1980s and '90s, which pitted environmentalists against logging companies. The owl's protection under the Endangered Species Act reshaped forest management, reducing logging of old-growth trees on federal lands.
Now the threat is not a logger with a chain saw. It is a fierce and formidable avian competitor. Though the species are closely related, barred owls are more aggressive, squeezing out the smaller spotted owls for prey and nesting sites. They are also more adaptable and breed more rapidly, producing more young, according to ornithologist Jack Dumbacher of the California Academy of Sciences.
With dark eyes and brown stripes resplendent on its breast, barred owls “look like they're cut out of wood” that's been furrowed by insects, said Bolinas naturalist and bird illustrator Keith Hansen, who raced out the door of his studio on Sept. 17 to video-record the visitor.
By the next morning, despite a careful search by Point Blue Conservation Science ecologists, it was gone.
Silent and sleepy during the day, barred owls at night have a loud hooting call, described as “Who cooks for you? Who cooks for you-all?” that carries well through the woods. They have a variety of other barks and screams that sound like monkeys or a maniac with a cigarette cough.
The owl's call is popular with Hollywood sound engineers, said Hansen. “It's the voice you hear in every jungle movie, whenever someone is lost in the woods.”
Native wildlife has been slow to appreciate the owl's menace. What's at risk aren't just spotted owls, but other creatures, as well, Merkle said.
“They're preying upon species that haven't evolved defenses to them,” he said. While spotted owls stick to a narrow diet of wood rats, he said, barred owls eat whatever they find: slugs, crayfish, endangered shrimp and amphibians such as California redlegged frogs.
Native to the Eastern U.S., barred owls traveled westward in the late 1800s along with farmers and ranchers, who created friendly habitats by suppressing wildfires and planting trees. Barred owls began invading spotted owl territory in British Columbia in 1959, then expanded into Washington and Oregon around 1970, reaching California by the mid-1970s.
The intrusion into Marin County was detected by Hansen in 2002. While bicycling with a friend at dawn on the flanks of Mount Tamalpais, he imitated an owl call and “in five seconds, `Boom!' I hear the concussion of this thing landing on a branch, pissed off and fluffed out.”
The first successful breeding was seen in 2007 at Muir Woods National Monument. In recent years, they've been spotted not just in Marin County, but also in Sonoma County, the San Mateo County village of Pescadero and Tahoe National Forest. A feather was found in Concord.
In Olympic and Redwood National Parks, spotted owls have been almost completely replaced by the barred owl.
But Marin County still hosts a healthy and stable population of spotted owls. Large corridors of state, local and national parks, coupled with agricultural lands, have preserved an estimated 110 “territories” for the owls, most of them used by breeding pairs.
The intrusion of barred owls has been slowed by an inhospitable geographic barrier — the Petaluma Gap, a windy and treeless breach in the coastal mountain range.
The species is also closely monitored, and shot, by Marin's vigilant wildlife biologists.
When a sighting is reported, they rush to the area. Using a recorded bird call, the biologists lure the territorial owls within reach.
“The most humane way to remove them is with a shotgun,” Merkle said. “It's very surgical. There's a crack, and then the bird falls.”
Biologists have tried alternatives, such as capture and euthanasia, but that's more stressful for the animals, he said. They have also tried to find adoptive homes at zoos and museums, but supplies are saturated. Nobody wants the owls.
Without the protection of a widescale elimination strategy, the spotted owl is in a much more dire situation than it was decades ago, said Merkle and Press. If the new plan is approved, will it rise to the challenge in time?
Spotted owls are virtually extinct in California's northern forests, said Press.
“In Marin County, if we do not get a handle on the barred owl invasion,” he said, “they'll be extinct here as well.”