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Will fake cactus habitat stick?

Scientists plant green contraptions in Irvine Ranch Conservancy to entice imperiled wren.

September 12, 2008|Mike Anton | Times Staff Writer

At first glance, the 6-foot-tall tangle of pipe wrapped in a blanket of barbed wire could be mistaken for a lot of things: a plumbing project gone terribly awry. A robot from a low-budget 1950s sci-fi flick. Maybe a piece of modern art.

But a cactus?

Scientists experimenting with ways to restore the coastal habitat of a beleaguered bird hope so. In recent weeks they've planted 15 of these homemade, green-painted contraptions on fire-scarred hills throughout Orange County's Irvine Ranch Conservancy to try to entice a declining population of cactus wrens to nest.

"There's no textbook on this. We're starting at zero and using our intuition as to what the birds might like," said Jutta Burger, a senior field ecologist for the conservancy, which manages thousands of acres of open space. "You need to think like a cactus wren."

Wildfires have wiped out countless acres of cholla and prickly pear cactus throughout coastal Southern California. Cactus wrens nest in these thorny thickets, which protect them and their eggs from predators, particularly snakes.

Campylorhynchus brunneicapillus is part of the fabric of the Southwest, a bold songbird whose scolding monotone -- char-char-char-char -- can be as grating as an "American Idol" contestant.

"Cactus wrens in the desert are super-adaptable," said Robb Hamilton, a Long Beach biologist and consultant who has studied the bird locally. "They're aggressive. You'll have cactus wrens stealing your food, getting into your car. They're somewhat of a pest out in the desert."

Along the coast, however, cactus wrens are "on the verge of collapse," Hamilton said. Development has been chewing at their habitat for decades. Now, fire is gobbling up much of the rest. And unlike their desert counterparts, coastal cactus wrens are extremely picky about where they nest, exacerbating the problem.

Cactuses under 3 feet tall are looked upon by coastal wrens with the kind of disdain a Hummer owner might feel toward a Prius. It can take 25 years for a plant to grow big enough to interest a pair of mating cactus wrens.

"We can't tell why they are so finicky," Burger said. "But we're stuck with the fact that they are."

The 1993 Laguna Canyon fire scorched 13,000 acres, including large swaths of mature cactus. A 2006 survey found that the number of cactus wrens had declined by nearly 60% in the burned area, where most of the new plants are a decade away from being large enough for nesting.

The fires that swept San Diego County in 2003 and 2007 destroyed valuable habitat. So did Orange County's Santiago fire, which last fall turned patches of the region's best remaining cholla cactus into charred skeletons.

If the Irvine Ranch Conservancy's fake cactuses attract wrens, more could be deployed as part of a planned replanting of real cactuses throughout the region.

"We're hoping we can tide them over with the artificial structures" until the new plants mature, Burger said. "It's kind of an emergency situation. In the next five to 10 years, the species could be gone in this area unless we do something."

In recent decades artificial nesting sites have helped a number of declining bird species bounce back, including eastern bluebirds, barn owls, peregrine falcons and bald eagles. In the eastern U.S., purple martins have become completely reliant on man-made houses in numerous backyards.

But dialing into a bird's evolutionary preferences for housing is an inexact science.

When Mission San Juan Capistrano was renovated two decades ago, old mud nests in eaves and archways used by the returning swallows were destroyed. Ceramic nests were installed in their place to entice the birds back to their romanticized spring and summer home.

Turns out swallows prefer mud. The birds still return to San Juan Capistrano, but now they head for a nearby Wal-Mart, a community college or under a freeway overpass.

Artificial nesting sites are "not going to fix every problem," said Tina Phillips, a biologist at the Cornell Lab of Ornithology in New York. "A lot of it is trial and error."

It won't be known until spring whether Orange County's fake cactus will attract wrens. In Laguna Canyon Wilderness Park, Burger trudged up a hill to one of two models being tested. It looked like a squat cellphone tower amid patches of real cactus.

From nearby came a piercing char-char-char-char. Burger pulled out binoculars and watched the wren watching the cluster of green pipe. Its head cocked back and forth -- a prospective buyer at an open house.

"He's angry at us. We're in his territory," she said. Burger grabbed a handful of dried grass and stuffed it between the barbed wire like a Realtor putting out freshly baked cookies. "Make it look more natural," she said.

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mike.anton@latimes.com

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