Six plywood homes were built this month next to the futuristic, blue-roofed Marin County Civic Center as part of an innovative, and slightly desperate, attempt to persuade owls to police the building's rampaging rat population.

The wily rodents have been wreaking havoc on government property at the San Rafael center. The buck-toothed vermin, it turns out, are a delicacy to barn owls, a family of which can gobble between 3,000 and 5,000 a year.

"Barn owls are most beneficial to man in controlling rodents, because they are cavity nesters and are easy to attract," said Alex Godbe, program director and founder of the Hungry Owl Project, which built the owl domiciles in cooperation with the county. "They are superb hunters with large appetites. Also, the barn owl is nonterritorial, so you can attract as many owls to an area as there is prey to eat."

Thus the owl boxes, five of them mounted on 10-foot posts and one in a tree. The boxes, constructed on Sept. 10, have holes in the front and were placed on the west side of the Civic Center, where experts said the nocturnal birds would best be able to see and hear the rodents tiptoeing in the dark.

"It's all location, location, location," said Ed Hulme, the coordinator for the Marin County Integrated Pest Management Program. "Typically, barn owls start looking for the wintertime nests in the fall, so we're hoping they move in soon."

Raiding the garage

If you ask county workers, the move-in date can't be soon enough.

The rat population multiplied last winter into what can only be described as an unruly mob. The ravenous rodents began sneaking out of the tall grass after dark into the warm confines of the Civic Center garage, where they developed a taste for the internal mechanisms of county vehicles.

Electrical systems, tubing, upholstery and carpet were ripped out and used as nesting material. The pointy-nosed rodents chewed through a plastic reservoir in one vehicle, allowing brake fluid to spill out. They disabled a backup generator and built nests in engines. They did not have the courtesy to use the Civic Center restroom, either.

"It's the worst we've seen in years," said Hulme, who estimated the damage at between $5,000 and $7,000. "At one point, we had eight vehicles that were damaged within a two- to three-week period. It was a mess. Had anyone driven off without brake fluid, it could have been even more ugly."

The county does not use poisoned bait anymore, Hulme said, so the grass was cut and rat traps were placed around the garage, but it wasn't enough to stop the scurrying hordes.

Restricting poisons

Godbe started the owl project in 2001 in partnership with WildCare, a nonprofit education and wildlife rehabilitation center in Marin County. The group began installing owl boxes in vineyards three years ago in an attempt to control rodents without using poisons.

It's important, she said, because poisoning rodents is a major environmental concern. Studies in Canada, the United States and Europe have shown that rat poisons have contributed to the deaths of mountain lions, foxes, deer, squirrels, possums, bald eagles, golden eagles, hawks and vultures, among others.

One study analyzing owls found dead in British Columbia and the Yukon Territory showed that nearly three-quarters of the birds had rodenticides in their livers.

The project has installed owl boxes in 25 vineyards in Marin, Sonoma and Napa counties. Several hundred have also been placed in suburban neighborhoods, on ranches and in parks throughout Marin, she said.

Barn owls do not build their own nests. Instead, they look for holes or cavities in trees, often where hawks, ravens and other birds have abandoned nests. This, Godbe said, is why owl boxes work so well.

The boxes at the Marin Civic Center each have a hole in the front large enough for a barn owl to enter, build a nest and raise five to seven chicks. The roofs are shingled to keep out the rain and the posts are covered with a slippery metal material so raccoons and rats cannot climb up and kill the owlets.

The total cost of the project was $990, most of which came from grants, said Maggie Sergio, a director at WildCare.

"For poisons, you pay pest control companies thousands of dollars every month, depending on how big the area is," she said. "Here we are looking at under $1,000 for free rodent control. It's definitely a more sustainable way to control rodents without putting out poisons, which kill everything in the food chain."

It is the second time the owl project has installed boxes at the Civic Center. Three boxes were placed there a few years ago in a successful attempt to draw out an owl family nesting in the building's spire. A breeding pair now occupies one box, another one is empty and a bee colony has inhabited the third, Godbe said.