Shooting Owls

Small experiment studies whether spotted owls thrive when barred owls are removed



The little white mouse in Lowell Diller's hand could have jumped. It could have beaten a path up his arm and found refuge in the folds of red flannel. Instead it just stood there on his gloved hand, too tame or too nervous to make a move. Diller's dogs sat perfectly still, eyes on the mouse, ears pricked. Out of the dark came the faintest flurry of wings, a swift shadow in the dim light -- an owl, flying away, clutching the little white mouse.

Diller is the head biologist at Green Diamond Resource Company, and he's out on a routine survey of northern spotted owls on Green Diamond land. Twenty years after it was listed under the Endangered Species Act, the spotted owl is being forced out of much of its range by its cousin from the East, the barred owl. While the U.S. Fish and Wildlife Service slowly works toward an experiment to find out whether removing barred owls can save the spotted owls, Diller and the California Academy of Sciences are already two years into a study that's been removing barred owls from some Green Diamond forests.

Maple Creek Road twists and turns up through the redwoods, past mossy barns and lush pastures. To the west, the Mad River is a blazing ribbon in the setting sun. A log truck rumbles by, headed for the lumberyards at Korbel. Diller's dogs crowd the center consol. Riley, a liver-and-white Brittany, stares at the road ahead. The other dog, a little black poofball named Cosmo, is too short to see over the dashboard, and he races back and forth around the cabin.

Blacktop switchbacks turn to gravel, then packed dirt past a locked gate. Diller doesn't slow his dusty white Ford Expedition for overhanging brush or potholes, but slams to a stop when a covey of quail chicks appears around a bend, meandering single file across the road. Finally the road through the woods is just fresh bulldozer tracks on soft earth, with newly knocked-down brush and small trees at the margins. Diller parks in front of a break in the vegetation that he says is probably the trailhead.

The dogs scramble out of the truck and fan out in snuffling circles as Diller loads his backpack. He pulls out a wooden box. Script on a painted yellow banner running across the lid reads, "Diller's M.A.D." His art-major daughter painted the box for him, he said; M.A.D. stands for Mouse Accommodation Device. He pulls five or six squirming white mice from the M.A.D. and sticks them in an air-holed Tupperware that he places in his backpack. "Let's go, Riley," he says, and heads into the woods.

The trail is quickly lost, overgrown and obscured. Diller is 64, but he busts through thick brambles and clambers down thicketed slopes with ease. "You love being in the field, that's why you get in this business," Diller says. As head biologist, conducting surveys isn't even part of his job description anymore, he says ruefully. Diller is mustachioed, burly and dressed in flannel over an old T-shirt. He's a lifelong hunter who prides himself on having raised his daughters on the grouse, quail, and waterfowl he brought home. Today though, the shotgun stays behind.

Diller breaks through a last line of underbrush out onto a small stream. "Whoooo!" He raises his hand to his mouth and gives a convincing owl hoot. He looks around. "Where's the trail, Riley?"

Spotted owls, Strix occidentalis, and barred owls, Strix varia, are each other's closest relatives -- so closely related that they can interbreed and produce fertile offspring. They look similar, with dark eyes, rounded features and brown plumage, and as nocturnal rodent-hunters in big, dense forests, they both fill the same niche. Both birds must have a territory to defend to attract a mate and reproduce. They're natural competitors, but it's not quite an even fight. The barred owls are just a little bigger and heavier -- and more aggressive.

Nobody can say for sure how barred owls got to the Pacific Northwest. For hundreds of thousands of years spotted owls and barred owls stayed on separate sides of the continent, but sometime in recent history -- scientists believe around 100 years ago -- the barred owl began its push westward. There's no question that the Great Plains were once the barrier that kept barred owls confined to the east, but there are multiple theories on what helped the owls bridge the gap, said Fish and Wildlife biologist Kent Livezey.

One idea is that climate change allowed the owls to venture farther north into existing forests. Another theory holds that European colonization of North America let the barred owl expand its range. For thousands of years, the plains tribes set fires regularly, which kept the landscape easily navigable and improved the land for subsistence gathering, while keeping fast-growing cottonwoods and other trees at bay. Europeans stopped the Native Americans from burning the plains, and suppressed natural blazes. Without regular fires, strips of forest sprang up rapidly along rivers and streams. Additionally, European homesteaders planted trees wherever they settled, to provide shade and block the wind. Where once existed open grasslands, trees grew, and owls followed.

Simpson Timber Co. contracted Diller to conduct a survey of spotted owls on its lands in 1989. He was in Idaho studying rattlesnakes, on sabbatical from a teaching gig at Frostburg State University in Maryland. The spotted owl was making headlines, and Simpson's managers knew they had to find out how many of the owls they had on their land, and fast. All predictions were that the spotted owl would soon be listed under the Endangered Species Act, Diller said, and the timber companies saw trouble brewing. Simpson wanted Diller's help in crafting a habitat conservation plan. HCPs are an addition to the Endangered Species Act of 1973, and are essentially contracts between the federal government and companies or private individuals with endangered species on their land. They allow those landowners to set aside a portion of their property as critical habitat for the species, while continuing their activities in other areas. Without an HCP, timber companies could be held liable for destroying owl habitat.

Diller, however, didn't have much hope for finding spotted owls on Simpson's land. Conventional wisdom at the time said that spotted owls lived in dense stands of old growth timber, not second or third growth forests like Simpson's. "I remember when I recruited students to help with the survey, I told them not to expect to see a single owl all summer. It was like looking for Sasquatch -- probably pretty boring," Diller said. "My gosh, I couldn't have been more wrong."

A young spotted owl, perched in a big leaf maple, stares as Diller fiddles with a cat toy on a string. Brown downy fluff sticks out in all directions, giving the bird a shapeless, disheveled look. Cosmo and Riley sniff among the ferns and bushes below, but the owl's attention is focused on the gray toy rodent, which squeaks a little as Diller moves it.

Watch out for the adult, Diller warns. Once he captures the juveniles for banding, the parent is likely to start dive-bombing. "Keep your hand up, like this." He demonstrates, holding his bent arm in front of his face. "I've been hit in the face before," he said. As if on cue a full-grown owl, the mother, appears directly above on a redwood branch. She's brown, with white flecks that make her hard to spot against the redwood needles silhouetted in the twilight. Farther up in the tree the second juvenile lights on a branch. The two young owls start whining, a high-pitched begging call. They're hungry.

Diller tosses the cat toy and line over a branch and bobs it up and down. The three owls are enthralled. The idea, he explains, is that one of the juveniles will try to get a little closer to the toy, close enough for Diller to place his slipknot around its neck and bring it in for banding. He'll put a Fish and Wildlife band around one leg, which has a unique identifying number for that owl, and a colored band around the other leg to show the bird's gender. He's been banding owls on the Green Diamond ownership for 20 years, which means he has two decades of owl demographics to use for comparisons with his removal project.

The young owls, however, aren't cooperating. They seem content to hoot encouragement as their mom swoops after the toy. One of them lands on a branch just... out... of... reach. It doesn't react as Diller stretches and strains to maneuver the owl-catching pole and noose over its head, recoiling only slightly when Diller jostles it.

The juveniles are still too young and hesitant to swoop in, Diller finally concludes, and he lets down the cat toy. He pulls out his Tupperware. Mousing is the best way to catch adults, he says. You simply hold a mouse in your hand, and when the owl comes to snatch it, you grab the owl. Today, however, he's just going to let the mother take the mouse, with the hope that she will share it with her offspring -- on a low branch.

He puts a leather glove on his right hand and holds out the mouse. The owl is a dark blur in the dim light, too fast for the eyes to focus on. As Diller lets his hand back down the three owls are already dismembering the mouse, high in a tree, far out of range of the owl-catching stick. The dogs go back to patrolling, and Diller mutters at the owls about finding a lower branch. He pulls out another mouse.

Biostitute. That's a combination of biologist and prostitute, Diller explained. It was a word that got thrown around a lot during biology summits in the early 1990s, he said, and it means what it sounds like. When he first reported the results of his findings on Simpson managed forests he was accused of selling out, fudging the results.

"All of us were a little suspicious," said Eric Forsman, a Forest Service biologist who conducted some of the first studies of spotted owls in Oregon in the 1970s. Diller was the new kid on the block, Forsman said, and worse still, he worked for the timber industry. Over time though, he said, it became obvious that Diller was telling the truth. The Simpson forests, as it turned out, were full of spotted owls.

The first studies of spotted owls were in Oregon, where their primary prey is the flying squirrel. The squirrels eat fungi, which grow on downed logs and other decaying matter. Younger forests can't sustain the squirrels, so logging old growth forests there destroys both the owl's habitat and the habitat of its primary prey. The studies in Oregon set the precedent, but the situation on the redwood coast, Diller found, was not the same.

"Everybody's vision of a spotted owl was an animal that lived in large, contiguous plots of old growth," said Diller. "Here we were saying, ‘We're finding all kinds of them, and they're in patchy second-growth forests.'"

The key, he said, is the dusky-footed woodrat. Woodrats, a variety of packrat, build heaping nests of sticks and other debris in forests. They eat the new, tender parts of plants, such as redwood shoots, which are more accessible in young forests than in older forests. The forests on Green Diamond land are second and third growth -- full of new foliage, and full of woodrats.

But smaller trees don't make good nesting sites for spotted owls. The other piece of the puzzle, Diller said, is that when loggers first cleared the area in the early 1900s, they didn't cut down every tree. The seemingly endless forests of the time meant that loggers were a little picky about which trees they took. Some trees were imperfect, or too hard to get to, so they left them alone. "Sloppy clear-cutting is what we call it," Diller said. "It turns out it was very lucky they did that." The very features that the loggers avoided, namely snags and cavities, make a nice home to spotted owls. "Within a landscape, you need areas where you have young forests, because that's where the woodrats like to be, and of course you need the older forest," said Diller. "You need the mixture."

Diller originally planned on returning to Maryland after a year or two, but the allure of the forest was too much to deny. He signed on full time with Simpson -- now Green Diamond Resource Co. -- and continued his studies of the spotted owls thriving in the timber company forests throughout the 1990s.

The barred owls were on their way. Up through Manitoba, across Alberta, and into British Columbia they spread. Two barred owls were reported in Washington State in the 1960s, and they first reached Oregon and California the decade after. While the barred owl population exploded in Washington and Oregon, their numbers remained low in Northern California until the late 1990s. The rapid expansion happened around 2000, Diller said. "Until then we'd see the occasional barred owl, but they were kind of seen as a novelty."

Kristin Schmidt, a wildlife biologist at the Redwood National and State Parks, has seen the number of spotted owls drop steadily during her 11 years at the park. The original inventory of the parks in the early 1990s turned up around 40 spotted owl territories. Last year when they surveyed the park, biologists only found five or six spotted owl territories. Meanwhile the barred owl population has skyrocketed. She estimated there could be as many 50 barred owl territories.

Broadcasting territorial calls and listening to the replies is the main method of counting both spotted and barred owls. While barred owls readily respond to both barred and spotted territorial calls, spotted owls don't answer to barred owl calls, nor do they answer to spotted owl calls if there are barred owls around. "We either have lost our spotted owls because of the barred owl invasion, or they are there but not responding to the surveyors," Schmidt said. "They're not the easy animal to study that they once were. It's quite sad."

Schmidt was experiencing what researchers in Washington and Oregon had gone through years before. Barred owl numbers soared, and spotted owls disappeared throughout their range, out of sight or gone altogether. In its June 28, 2011, Revised Recovery Plan for the Northern Spotted Owl, the Fish and Wildlife Service called the barred owl one of the biggest threats to the survival of the spotted owl. One way to deal with the threat, the report said, would be to actually remove the barred owls. First though, Fish and Wildlife needs to conduct a study to see whether the spotted owls will even come back if the barred owls are removed.

Fish and Wildlife biologist Robin Bown, who is leading the work on the environmental impact statement for barred owl removal experiment, said that the agency is at least a year-and-a-half out from any experiment that would remove barred owls. First it has to complete the environmental impact statement, estimate costs, and settle on a method of removal. Removing the owls alive is an option. Capturing barred owls with nets, however, is difficult, time intensive, and costly. Bown said capturing the owls alive only to release them later in unfamiliar territory is morally questionable. "Realistically, it's shoving it under the carpet so you don't have to watch the birds die," said Bown. Shooting the birds, on the other hand, is relatively simple and cost effective. The process begins the same way as banding: Use territorial calls to draw the barred owls out, wait until they land on a branch and are easy to hit, and shoot them with a shotgun.

Bown said that while most scientists are in agreement that a study on the effectiveness of barred owl removal is necessary, there is no consensus about the long-term prospects of the spotted owl.

"It's just crazy to kill owls to save owls," Len Yannielli said into the phone in a loud, exasperated voice. Yannielli is a biologist and evolutionary studies professor who studied barred owls in Connecticut. He said that even if removing barred owls does allow the spotted owl to reestablish itself in the short term, the wave of barred owls will keep coming. Removing barred owls could turn into an annual chore. There is a solution to save the spotted owl, Yannielli said, but it's much more difficult and long-term than removing barred owls. "The main way to shift the advantage to the spotted owl is to save the old growth forests. That's what they're best attuned to," he said. "But that doesn't happen by itself. That's gonna take a lot of work."

The sheer numbers involved in large-scale removal could be daunting. According to a 2008 report, barred owls probably outnumber spotted owls by 3-1 in many parts of the spotted owl's range. Consequently, multiple pairs of barred owls would have to be removed to make room for one pair of spotted owls, especially in areas where spotted owls no longer occupy their historical territories. In his 2010 paper Killing Barred Owls to Help Spotted Owls I: A Global Perspective, Livezey concluded that thousands of barred owls would have to be killed to conduct the large-scale removal project described in the earlier report.

Diller thinks that scientists might not have to remove barred owls very far into the future. "People see how tame spotted owls are and think they're stupid," he said. "But the first time you give them a mouse they'll start following you through the woods. They show amazing ability to learn." He said that if some spotted owls learn to adapt to the barred owls, and are able to nest, forage and reproduce successfully, their offspring would pick up those behaviors. In that scenario, spotted owls and barred owls could reach a sort of equilibrium relatively quickly. For now, Diller said, the spotted owls need help, which means removing barred owls, but with that helping hand they might make their own solution. "If we give these birds a chance they will very likely adapt, and we won't have to shoot barred owls forever," Diller said. "At least that's my hope."

Fish and Wildlife biologist Brian Woodbridge, who made some of the first field observations on the effect of removing barred owls from spotted owl territory in the mid-2000s, said that it's really too early to tell how the situation will play out long term. Until the removal experiment is completed and the resulting data analyzed, nobody really knows what the best option will be. "We have a steep learning curve ahead of us," Woodbridge said. In the meantime, biologists at Fish and Wildlife are keeping a close eye on the removal experiment on Green Diamond land.

The Milky Way is clearly visible in the night sky, framed by the black outlines of leafy boughs. Diller is parked alongside Bair Road, on the Redwood Creek side of Lord-Ellis Summit. The banding effort didn't bear fruit -- it got too dark and made the birds impossible to spot, let alone capture -- and so he drove to the other side of the hill to have a look at the barred owls there.

A louder-than-life owl call blares from a speaker on top of his truck and echoes in the trees. Again and again the call sounds, a multiple-note string that ends in a gurgle. The call is different from the spotted owl's: It's a chaotic, echoing, Halloween-night sound. Cosmo whimpers, and tucks his stub tail between his legs. "Cosmo, you coward," Diller says and lifts the little dog into the truck. "He's been buzzed before by the barred owls," he explains.

In the distance, far back in the trees, an owl returns the call. "That's the female," Diller says. Her calls get louder, closer, and soon her mate joins her. They're hidden in the dark foliage but it is clear from their hoots that they're nearby. One soars out from behind the leaves and lands with a crash in the tree overhead. Probably not out of clumsiness, Diller says, but to intimidate. Its mate slams into the leaves higher in the tree. This is the control side of the hill, the side where the barred owls haven't been removed.

The female owl glowers at Riley and Diller. The white bands of plumage on her face and body are ghostly pale in the beam of Diller's headlamp. She's just 20 feet distant. She would make an easy target.

Jack Dumbacher maneuvers his way through narrow corridors between towering, off-white metal specimen cabinets. The air is cold and dry, and the florescent lighting is dim. He is deep in the vaults of the California Academy of Science in San Francisco, surrounded by the physical remains of thousands of birds and mammals -- a crypt, of sorts.

Dumbacher opens a drawer and steps back to reveal half a dozen stuffed spotted and barred owls. Their wings are folded against them, and their eyes are gone, replaced with bright white cottonballs. They're genetic samples, not trophies, Dumbacher explains; they don't need to look good. He lifts a tag that's tied around one of the barred owls' legs. This bird is from 1896, it says. Next to it is an identical owl. Dumbacher reads its tag: 2009, it says. Diller shot this bird.

In the mid-2000s, around the same time that the Fish and Wildlife Service first contemplated experimenting with removing barred owls, Dumbacher was looking to get his hands on some barred owls for the museum, which had no specimens from the Western United States. When Dumbacher acquired a permit to collect 20 barred owls for the museum, Fish and Wildlife suggested he remove them from an area where barred owls were suspected of displacing spotted owls.

Woodbridge, the Yreka Fish and Wildlife biologist, monitored the project, which took place near Mount Shasta in the Klamath National Forest. The results surprised him. In one case, when Dumbacher killed the barred owls in one territory, a spotted owl appeared within 24 hours and responded to territorial calls. They recognized the owl; it had their bands around its legs. It was an owl they hadn't seen in more than three years. He had been living in the shadows, unable to find a mate and reproduce. If he hooted he'd be challenged by barred owls. With the barred owls out of the way, he came out of the shadows and claimed his territory, said Woodbridge. That study was too small to make too much of, he said, but the results were promising.

Dumbacher still wanted more samples, and Fish and Wildlife still wanted to conduct a pilot study before it completed its environmental impact statement and started a larger study. They both looked to Diller -- if he could conduct a relatively small removal experiment on Green Diamond's private land, he wouldn't need to bother with the environmental impact statement necessary for a study on public land. Dumbacher would get his samples, Fish and Wildlife would get its pilot study, and Diller would be on the front lines, working to save the owls he had studied for more than 20 years.

The experiment is divided into six areas, totaling around 380,000 square acres: three treatment areas, where all the barred owls are removed, and three control areas, where no owls are removed. Using the data from spotted owls he has banded, Diller is able compare the survival, reproductive, and occupancy rates for spotted owls in the treatment areas with the spotted owls in the control areas.

Even as biologists remove them, the barred owls' invasion continues. Since 2009, Diller and Dumbacher have killed 49 barred owls. Around half those owls were killed in different years, but in the same areas, meaning that new barred owls are replacing their slain brethren.

Still, removing the barred owls is having a marked effect on the spotted owl's fortunes in the treatment areas, Diller said. Before the study started, the number of spotted owls in the Korbel/Mad River treatment area had fallen from a one-time high of 58 mating pairs down to 37 pairs. Since the barred owls were removed from the area, the number of spotted owls had rebounded to 58 pairs by 2010, and is probably even higher this year, said Diller. He's seeing similar results in the other treatment areas.

Meanwhile, Dumbacher is gleaning valuable information from the dead barred owls Diller sends him. Hybridization of barred and spotted owls is particularly interesting to the museum. There is evidence that the two species have been interbreeding, but so far biologists don't know how widespread the hybridization is, or what it could mean in relation to the Endangered Species Act, which only protects full-blooded spotted owls. Having a genetic record in the form of skins, skeletons, and tissue samples is crucial to make future comparisons, Dumbacher said. "The idea is that we're taking a biological snapshot of our time."

On a rainy, windy day in February 2009, Diller pointed a gun at a barred owl the first time. He had called the owl; it sat in a tree looking at him. The sun was still up. Diller's mind raced. "I can't believe I'm actually gonna do this," he remembers thinking. "I'm gonna do this because this study is scientifically important. I'm a scientist, so I'm gonna do this." Then, "I'm not sure I can do this."

Years earlier, when talk of killing barred owls was still just an intellectual exercise, Diller vowed he would never shoot an owl. Recently, however, it had become apparent to him that the choice was between killing barred owls and watching spotted owls go extinct. His promise was untenable.

He stood eying the owl, heart pounding. He was used to shooting birds, but the owl felt different, foreign. The 20-gauge shook in his hands, and he worried he would miss, or worse, wound the owl without killing it. He braced himself against a tree to steady his aim, and squeezed the trigger. The owl dropped.

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