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City Planning for Owls

As development spreads in California's Silicon Valley, an effort is taking shape to leave enough real estate for burrowing owls

  • Bob Holmes
  • Oct 01, 1998
The nine-inch owl stands at attention in the sunlight, its dusty brown feathers blending with the fringe of dirt around the mouth of its burrow. Underground, three owlets wait for their next meal of crickets, beetles or--if they're lucky--a mouse. To all appearances, just another family of burrowing owls, eking out its quiet, rural living somewhere on the dry plains of the West.

Except that this burrow sits at the edge of a busy parking lot on the campus of Mission College in the heart of California's booming Silicon Valley. Just a stone's throw away, a brand-new multiplex cinema stands where other burrowing owls once lived. A short stroll in the other direction, past the glass-and-steel boxes of the Santa Clara Convention Center and various corporate offices, the broad hills of the roller coaster at Paramount's Great America amusement park loom against the sky. Even the burrow is urban--a length of pipe buried in a designer dirt mound, all courtesy of a small band of conservationists dedicated to helping the owls survive here amidst the bustle of the city.

With their aptitude for urban living, burrowing owls could thrive here given just a few acres of suitable habitat. But sky-high land prices have developers gobbling up every bit of undeveloped land in Santa Clara for more office blocks and subdivisions, and the owls find themselves squeezed out. "This is how you make an endangered species," says Dave Plumpton, an ecological consultant in Alviso, California, who has studied burrowing owls for years. "It's a recipe for disaster." Nor are their rural cousins faring much better. That's because prairie dogs and ground squirrels--the birds' favorite neighbors and the sources of most of their nest holes--are still persecuted throughout the grasslands of western North America. As a result, burrowing owl populations in areas of many western states and Canadian provinces are increasingly in trouble, though data are often sketchy.

But here in Silicon Valley, the owl's allies hope to keep it off the list of endangered species. At their urging, some of the valley's landowners and city planners are making a serious--though sometimes grudging--effort to set aside the open ground the owls need to survive. And the infant spirit of cooperation born here may go on to protect many more owls as well. "There's going to be development elsewhere, too; the Silicon Valley is like a crystal ball for what's going to happen elsewhere in the state," says Lynne Trulio, an environmental scientist at San Jose State University who has helped lead the effort to protect owl habitat.

Burrowing owls are the extroverted freeloaders of the normally reclusive owl clan. As their name implies, these owls nest underground, but only an isolated subspecies in Florida takes the initiative of digging its own burrows. Elsewhere, the owls expropriate them from prairie dogs, sometimes ground squirrels (as here in central California) and occasionally other hole diggers like badgers, foxes and tortoises.

Neighboring prairie dogs or ground squirrels keep the vegetation clipped the way the owls like it--short, so that marauding hawks or coyotes are easily seen--and add many pairs of eyes to sentry duty. "The mammals provide the housing start, the lawn service, the security system. If burrowing owls are providing anything, I don't know what," says Plumpton. Rumors that the birds share their burrows with rattlesnakes are false but understandable, says Plumpton. When trapped underground, the owls sometimes try to bluff humans and other predators by mimicking the buzz of a rattlesnake.

Each spring, deep in the safety of the burrow, the female lays as many as 11 eggs, the largest clutch of any bird of prey, from which she and her mate usually manage to fledge 3 or 4 owlets each summer. The owls need such large families to get by: Barely a third of fledglings survive predation, starvation and other rigors to breed the next year, and adult owls seldom live more than about 5 years.

During the breeding season, the owls' homes stand out from those of their rodent neighbors. Owls are messy tenants, leaving droppings and pellets of undigested food around the entrance. The male also decorates his doorstep with trophies he has collected on his daily travels--feathers, beetle wings, plant fluff--perhaps as a way of posting an "occupied" sign for other owls. (The Silicon Valley birds favor an urban aesthetic--aluminum foil, cigarette butts and shredded fast-food napkins.) And though the birds are most active at dawn and dusk, they often stand at the burrow mouth even in broad daylight, making them much easier for casual observers to see than other owls. "People love burrowing owls," says Brian Millsap, a wildlife biologist for the Florida Game and Fresh Water Fish Commission. "In neighborhoods down here that have burrowing owls, the owl is everybody's pet."

But good will alone does not seem to be enough to keep the owls thriving. Officially listed as endangered in Minnesota, Iowa and in Canada, the owls are also in trouble in several more states, from the Dakotas to California. In Canada, where estimates are more precise, owl numbers have been nosediving at a staggering 16 percent per year since the early 1980s, to a total of fewer than 1,000 pairs today. And in Nebraska, ecologists watched as a population of the birds in one area fell by 63 percent between 1990 and 1996.

Though burrowing owls themselves enjoy protected status under U.S. law in some parts of their range, that status does not extend to the rodents whose abandoned burrows form essential habitat for owls. "They're completely dependent on animals that have no protection," says Plumpton. The problem has been especially acute on the prairies, where poisoning programs have wiped out 98 percent of America's prairie dogs over the past century, leaving burrowing owls homeless in their wake. And ground squirrels are considered vermin that can be trapped, poisoned or shot with impunity.

In California, too, burrowing owls appear to be much less common than in past decades, and recent research supports the impression. Based on an extensive statewide count carried out in the early 1990s, biologist David DeSante of the Institute for Bird Populations in Point Reyes Station, just north of San Francisco, estimates that California now contains as few as 9,200 breeding pairs of burrowing owls. Of these, most live in two of the state's most intensively farmed areas, the Imperial and Central Valleys, where they nest in ground squirrel burrows along the edges of agricultural fields or in the dirt berms along irrigation canals.

Another area in the state with a significant number of owls, about 150 pairs, is the San Francisco Bay region, including Silicon Valley. When DeSante compared his count for this region to one made less than a decade earlier by other researchers, he found that the number of locations with breeding owls had dropped by more than 50 percent.

The reason is obvious to anyone driving through San Jose, Santa Clara or the other cities of Silicon Valley: burgeoning development. In 1995, builders were gobbling up open space at a rate of about 8 percent per year to put up structures such as condominiums and office buildings. "We're seeing an explosion of development in owl habitat," says Craig Breon, an environmental advocate for the Santa Clara Valley Audubon Society.

Ironically, open space is about the only thing the owls need to survive. Both the birds and the local ground squirrels seem quite content to nestle up against even the busiest human activity. Owls nest just off the end of the runway at San Jose airport, and others live in freeway cloverleafs or the fringes of golf courses. One pair at Mission College has front-burrow seating alongside the tennis courts. "They're remarkably human-tolerant, and they seem to do well right on our doorstep," says Plumpton. "It's as simple as setting aside a bit of habitat."

To be more specific, the owls need a scrap of land to nest on plus a larger grassy or barren area where they can hunt for food (mostly insects and mice but also tadpoles, fish, crabs or anything else small enough to catch; the birds aren't picky eaters). The California Department of Fish and Game reckons the birds need roughly an average of six and a half acres of foraging habitat per breeding pair, though Plumpton cautions that the size may be much greater in poor habitats. With the region's booming economy driving the cost of land up near a million dollars an acre in prime spots, the owls' homesteads could get very expensive.

Of course, developers would be forced to set aside the necessary land if the state or federal government lists burrowing owls under the Endangered Species Act. But even the owls' staunchest defenders think listing could do more harm than good, because too many landowners would see the birds as enemies, fearing that a listed species could block any plans for using their property. And the owls' habit of sitting in plain sight makes them especially vulnerable. "A couple guys with a .22 and a pickup truck could probably eliminate most of the birds in the state," says DeSante.

At present, the owls get some protection under the California Environmental Quality Act, which requires only that developers try to minimize their impact on the owls, a state "species of special concern." Armed with this small legal stick, the owls' supporters are trying a more cooperative approach. "We have a bird that is really charismatic, and if we can push a plan that gets everybody together before it becomes somebody's enemy, we really have a good chance not only of saving it, but also of developing a conservation plan that can be a model," says DeSante.

One early test of this approach came at Mission College in Santa Clara, a small college on a large campus that was home to 16 pairs of owls. In 1990, the college decided to lease about 70 of its 100 acres of open space to developers who wanted to build a shopping mall. Environmental scientist Trulio and Janis Taylor Buchanan, a former instructor at the college, got involved and eventually persuaded the college and the developers to make room for as many owls as possible on what remained of the fields.

Poring over the college's long-term land-use plan, Buchanan and Trulio identified all the little pockets of land that were not slated for construction and got the college to agree to preserve some as owl sites for the next 20 years. Several are in a field that will someday become a running track. To reduce the owls' dependence on ground squirrels, the college put in several artificial burrows--buried terra cotta pipes about eight feet long, with nest boxes at the ends--and agreed to mow regularly to keep the grass low.

The work has not been easy. Almost everyone involved, from college administrators to bulldozer operators, has had to learn to include the owls in planning their work. But once people see the owls and learn about their needs, they quickly become converts. "I even found workers would bring their kids to the site on weekends to show them the owls," says Buchanan. "They became as concerned as we are."

Today, owls still live on Mission College's campus, thanks to Buchanan and Trulio. But the college's owl conservation plan, like most compromises, has not been ideal. Only 12 of the original 16 pairs remain, and Trulio predicts that there may only be enough habitat to support about 8 in the long run. "In this plan, we lost a lot of habitat," she says. "That can't keep happening if we're going to preserve the bird in this area."

But support is building for Silicon Valley's owls. At the urging of the state fish and game department and the Santa Clara Valley Audubon Society, the area's cities have begun hammering out a regional conservation plan for burrowing owls. Even the Santa Clara Valley Audubon Society's Craig Breon recognizes that some of the valley's remaining open space must inevitably end up as subdivisions and office parks. To help buffer this loss, he hopes the cities will agree to manage the rest for the owls' best advantage so more owls can live on less land. For example, they might mow undeveloped land instead of disking it, which destroys owl burrows.

Ironically, some of the most promising future sites for burrowing owls are those with the most unsavory human past: garbage dumps. Reclaimed landfills, often revegetated as broad grassy expanses, aren't suitable for building, but they can make good parks. If planners construct earthen mounds atop these artificial prairies, ground squirrels and owls will move in happily. Already, two landfills along San Francisco Bay are home to owls, and Trulio hopes that more could be developed into new owl habitat as well.

Apart from these few promising first steps, the regional owl plan is so far little more than talk. But with San Jose, the valley's largest city, taking an active lead in pushing for the plan's development, the effort is gathering momentum. And that, owl advocates say, is a very good sign for burrowing owls everywhere.

"If this region, despite the land values, can really show that it can prevent a species from being listed, that's very hopeful," says Breon. With hard work, cooperation and a little luck, Silicon Valley's little urban owls could set a good example for other sprawling cities to follow in making room for their own wildlife.

Santa Cruz, California, journalist Bob Holmes visited the burrowing owls of Silicon Valley to write this article.

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