Prospect of Wren Control Doesn’t Faze Builders : Environment: Another bird, in the same habitat as the gnatcatcher, may upset developers’ plans. But the industry is supporting a measure that might head off controversy.

For many Southern California developers, the summer of 1991 has been a bit like sitting through a horror show.

First came the California gnatcatcher. Proposed on Sept. 5 for the federal endangered species list, the bird had some builders quaking with fear that federal protection would put thousands of acres off limits to the construction industry.

Now comes the endangered-species sequel: The cactus wren.

Although it has not yet caused the hoopla stirred by its avian neighbor, the 8-inch-long wren eventually could pose nettlesome problems for developers if federal officials grant it protection.

Conservationists say the wren’s coastal population is sliding toward extinction, and they have urged federal Fish and Wildlife Service officials to propose the bird for the endangered species list. A decision is due by Saturday.

If the service lets the wren join the gnatcatcher as a prospect for protection, it would kick off a one-year study before a final decision is made on the status of the bird, which numbers about 1,500 in Orange, San Diego, Los Angeles and Ventura counties.

The wren makes its home in clumps of cactus that dot a scruffy mix of vegetation known as coastal sage scrub, which also harbors the gnatcatcher and more than 40 other sensitive plants and animals. That same sage laces terrain coveted by the building industry.

“Hopefully, this will add some emphasis to the notion that we’re looking at an ecosystem that’s in bad shape,” said Ken Weaver, a high school biology teacher from north San Diego County who is pushing for protection of the wren. “Why else have two birds at one time been proposed for listing? Like the gnatcatcher, the cactus wren is a symbol of some pretty grave things happening to the sage scrub.”

While the bird’s status isn’t good news for developers, they have reacted so far with relative indifference.

Christine Diemer, executive director of the Building Industry Assn. in Orange County, said developers have been so engrossed in the gnatcatcher debate that they haven’t had much chance even to consider the cactus wren, let alone do battle over the bird.

In addition, because the wren isn’t scattered as widely across Southern California, fewer development projects stand to be affected if the bird is placed on the endangered species list, she said. Listing of the cactus wren would probably affect just a few thousands acres, slim pickings compared to the sprawling territory covered by the gnatcatcher.

“Certainly in Orange County the gnatcatcher has more of an impact, land-use wise,” Diemer said. “The habitat of the cactus wren can be more easily isolated.”

That isn’t always the case. There are even more wrens than gnatcatchers, for instance, straddling the routes for a trio of toll roads planned in southern Orange County. Biologists have sighted nearly 250 wrens--a full one-sixth of the Southland’s estimated coastal population--along one of the highways, the southern segment of the Foothill tollway.

But tollway boosters and captains of the development industry say they are confident that a newly hatched plan championed by the Administration of Gov. Pete Wilson can ensure the survival of both bird and builders.

Developers have banded behind the effort, which is slowly wending toward the goal of establishing large reserves of coastal sage scrub to protect the gnatcatcher, the cactus wren and other endangered species that make their homes in the fast-disappearing vegetation.

“We need this sort of comprehensive approach,” Diemer said.

The Fieldstone Co. in San Diego County has reached agreement with authorities to work toward preserving coastal sage at its sprawling housing development in Carlsbad. The Irvine Co., which proposed the conservation proposal to Wilson, has undertaken an $843,000 study in Orange County to spotlight potential sites for reserves.

With the wren issue coming on the wings of the gnatcatcher controversy, “It drives home the point that we cannot try to protect individual species. We’ve got to focus on the larger issue of the whole habitat,” said Michael Mantell, the state official shepherding the Wilson Administration’s effort. “Otherwise we’re mired in the permitting processes and litigation battles and we lose sight of the whole picture.”

Conservation-minded biologists don’t disagree with the state’s approach, but question whether it will yield results soon enough to protect the wren and other species teetering on the brink. In the meantime, they say, the wren warrants elevation to the list of endangered plants and animals.

“This is a very seriously threatened bird,” said Amadeo Rea, a research associate with the San Diego Natural History Museum who joined Weaver to petition the federal government to protect the wren. “They’re really in much more danger than the gnatcatcher.”

As its name suggests, the wren makes its home in the cholla and prickly pear cactus peppered amid the coastal sage. Its nest--built about three feet off the ground and carefully cantilevered between the spiked arms of the cactus--provides ample protection from just about every predator except a bulldozer.

The football-sized nests are condo-like structures of twigs and grasses woven together, complete with roofs and tiny openings. Each bird builds its own nest, which provides a home to rear their young and roost in at night. While other birds such as the gnatcatcher suffer during nasty weather, the cactus wren is often able to ride out a cold snap in its cozy quarters.

Biologists say the wrens are an energetic, almost pugnacious bunch. Although they feast mostly on insects and on fruit borne by cactus, some experts have seen the wrens graze on a rare delicacy--gnatcatcher eggs.

“Like any other animal, they’re not going to overlook a quick source of food, including a gnatcatcher egg if they come across it,” Weaver said. “But I wouldn’t look at them as a constant predator on gnatcatcher populations.”

Perhaps their most distinctive trait is their song, a staccato churring that many biologists describe as downright unharmonic.

“It’s like a car trying to start on a cold morning with a weak battery,” Rea said.

With their unusual voices and black and buff feathers spotted with dark splotches, the coastal wrens of southern Orange and San Diego counties are distinct from varieties thriving in the deserts of the Southwestern United States and northern Mexico, some biologists contend. The wrens in coastal Los Angeles and Ventura counties, however, are essentially twins of their desert cousins.

Despite such differences, Fish and Wildlife officials have clumped all the coastal wrens together for possible protection.

Ecologists say that if some sort of protection isn’t provided, the bird eventually will disappear.

“We don’t have to pave over every last bit of coastal sage scrub,” Weaver said. “There are places that people can live without taking away all our natural resources.”

Cactus Wren

Under consideration for federal endangered species protection is the cactus wren. An estimated 1,500 remain along the Southern California coast. About 8 inches long, the bird builds a football-sized nest for roosting and egg-laying, sleeps late and forages under leaves and on the ground for insects and spiders.

SOURCE: National Geographic Society, Audubon Society and Peterson field guides.