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Burrowing owls are the only North American bird of prey that nests exclusively underground. (Steve Mandel)

The Little Owls That Live Underground

Burrowing owls can thrive amid agricultural development and urbanization—so why are they imperiled?

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(Continued from page 1)

The burrowing owl is now listed as endangered in Canada, threatened in Mexico, and a national bird of conservation concern in the United States. In addition, nine states and four Canadian provinces identify the owl as endangered, threatened or a species of special concern. A subspecies that lives only in Florida is also accorded some protections.

California, which supports one of the largest burrowing owl populations in the United States, designated the burrowing owl a species of special concern in 1978. But since then, the bird has nearly disappeared from coastal regions along the length of the state as well as from the entire San Francisco Bay area.

Conservationists have argued for years that the bird needs additional regulatory protection. Ironically, burrowing owls adapt well to living with humans. The owl’s supporters believe that with proper conservation measures, burrowing owls and people can readily live side by side.

Biologist David DeSante, founder of a research and conservation organization called the Institute for Bird Populations, has found the burrowing owl population to be highly fragmented, generally declining and vanishing in some places. But DeSante also found a dramatic increase in the bird’s numbers along the earthen irrigation canals in Southern California’s Imperial Valley. This area, which represents only 2 percent of the burrowing owl’s range in California, now supports 70 percent of the state’s birds.

“Burrowing owls are an ‘abundant imperiled species,’ ” Barclay says. The large number of birds clustered in the Imperial Valley masks the significant losses elsewhere. And with so many birds in this unnatural setting, it leaves them vulnerable if the earthen irrigation canals are ever changed or the area’s ground squirrels are eradicated.

Part of the problem is that the owl’s preferred habitat—very short grass with burrowing mammals—is exactly the kind of land that is often slated for development. When developers plow or mow weeds to reduce the fire hazard in areas they plan to eventually build on, they can inadvertently attract burrowing owls—and later provoke battles with conservationists.

Three years ago, Scott Artis, a cell biologist, became infatuated with a dozen adult burrowing owls that he discovered near his new home in Antioch, California. But since last fall, Artis has watched the partially developed grassland two blocks from his home undergo a startling transformation as a developer prepared to build more houses.

First, chain-link fences posted with “No Trespassing” signs were erected around parts of the 25-acre parcel. Next, five-inch-square doors were installed in burrow openings in the ground. The “eviction” doors allowed animals to come out of the burrows, but not go back in. A few days later, the eviction doors were removed and sulfur smoke bombs were tossed inside to eradicate the ground squirrels. Finally, the burrow entrances were filled with earth. Although the birds tried, they were unable to return to their homes. No one can say where the owls are now or what might have happened to them.

“They are such a cute little bird, and they were there all the time,” Artis said. “Seeing owls in the daytime is not what you’d expect. Sometimes a family of six or eight would fly across the street and land at their burrow. It was incredible.”

Under the complicated and sometimes confusing regulations that govern the owl, unless a nest is active, a developer can relocate or evict the birds. Artis mounted a campaign to bring attention to the owls’ plight, which generated extensive media coverage in central California, and is continuing to lobby for stronger regulations for the bird.

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