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Posted by staff writer Lauren DiPerna

Coastal cactus wrens might be in trouble, but they’re also picky.

For two years, the birds, whose populations are crashing on the Orange County coast, ignored the artificial nest platforms erected to help them survive — until now.

“We were pretty surprised,” said biologist Robb Hamilton, who recently found the first pair of cactus wren babies inhabiting an imitation nest. “We were doing one last check and didn’t have high hopes.”

After the 1993 Laguna Beach fire and the 2007 Santiago fire, 90 percent of the cactus wren bird population had vanished from coastal Orange County, their preferred cactus habitat largely torched.

In response, biologists at the Irvine Ranch Conservancy built artificial nests for the birds. it took two years of trial habitats to get a pair of cactus wren to inhabit them; the first took up residence late last month.

“We have so few birds in the area that we can really test this idea on,” said Jutta Burger, a senior field ecologist with the Conservancy. “To have one pair choosing this box to nest in, and to chose it even over [existing habitats], I think that’s a really good sign.”

The wrens normally nest in prickly pear or cholla cactus that are at least three feet high, safe from snakes and other ground predators. once destroyed, these cactus can take 30 years to reach one meter in height.

The Conservancy originally hoped to build artificial cactus as temporary nesting grounds in areas where cactus wren forage, while the burned cactus grew back.

Their first two models showed little more promise than some birds perching on them.

“We had heard of a case in Los Angeles of a cactus wren pair nesting successfully on a telephone pole that had a metal transmitter,” Burger said. “It was adjacent to the cactus scrub, and for some reason the cactus wren chose [the telephone pole].”

That was the moment that clicked for conservancy biologists.

“‘Wait a minute, here are coastal cactus wrens that have chosen to nest in an artificial structure and they nested successfully,’” Burger said of their thought process. “‘what is it about that structure that was attractive?’”

For the final trial nest design, the Conservancy provided Laguna Hills High School students with wood, metal grates, and field pipe posts.

With the L.a. story in mind, the students made the nests higher than the surround cactus scrub, added a wire grate on top for protection, and built them more accessible and sturdier than before.

There are many factors going against the cactus wren, but so far fires appear to be the worst.

The cactus wrens are not good at dispersing and  finding new areas to inhabit. The birds that in the past were able to move between the northern and southern parts of the historic Irvine Ranch and open space lands are now confined to areas between stretches of  burned cactus, said Hamilton, a biological consultant.

With these new nests the birds can forage for insects and live safely in areas cleared of  tall cactus.

If the wren becomes locally extinct, said Hamilton, “we wouldn’t have cactus wrens to enjoy. it would just leave us a little more impoverished.”

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For cactus wrens, hope in a box – OC Science : The Orange County Register