As its name suggests, the wren makes its home in the cholla and prickly pear cactus peppered amid the coastal sage. It builds nests about 3 feet off the ground, carefully cantilevered between the spiked arms of the cactus providing 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 a roof and tiny opening. Each bird builds its own nest, which provide a home to rear 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 fruit borne by cactus, some experts have seen the wrens graze on a very 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 wrens together for possible protection. The entire contingent, they reason, has been cut off by development from the inland birds.
"What we have found is that likely due to human disturbance, the wren's coastal population now appears to be disjunct from the rest of the species," said Jeffrey Opdycke, the wildlife service's Southern California chief. "The avenue of genetic interchange with the desert birds in San Bernardino County as well as the connection south into Mexico has been cut off by development."
Even now, the birds continue to disappear, ecologists say.
"They've just been taking a tremendous thrashing in the last six months," said Fred Roberts, assistant curator at UC Irvine's Museum of Systematic Biology.
With such episodes as a backdrop, the stakes are great in the debate over the cactus wren, ecologists say, contending that if some sort of protection is not provided, the bird will eventually 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."
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.