This summer, zoologist David Olson and his colleagues will hike into Orange County’s coastal sage reserves lugging 100-pound, 9-foot-tall jumbled frameworks of PVC pipe bristling with barbed wire and metal needles. Olson, director of science at the Irvine Ranch Conservancy, will look for domed nests of woven grass tucked into dense cactus patches. When he finds one, he’ll place his contraption nearby. Setting an iPod to coastal cactus wren, the scientists will broadcast a series of “char, char, char” notes. If they are lucky, a brown-and-white bird will flit out of the brush and perhaps make the tangle of piping and barbed wire its home. Olson’s fake cholla are part of a last-ditch effort to save the coastal cactus wren. It’s a manmade solution to a manmade problem — frequent wildland fires.
With a catastrophic rise in wildfires over the past two decades — most of them sparked by human activity in this rapidly developing corner of California — thousands of acres of hard-won coastal sage reserves have gone up in smoke. The wren’s population has consequently plummeted. The bird nests only in mature cacti at least 3 feet tall, and such stands take decades to recover from burning. Cactus wrens are also loath to venture beyond intact coastal sage scrub, an unfortunate trait for a bird whose habitat is becoming fragmented by development and wildfires.
Conservationists know that they cannot snuff out all of the wildfires, which are sparked more frequently by powerlines, cars and arsonists than by lightning. But they are trying to reduce the frequency of fire within the preserves, to maintain the coastal sage scrub and cactus that the bird depends on.
“If we reduce the probability of these fires by 50 percent, which I think is entirely doable, we’ve just doubled the fire interval,” says Michael O’Connell, executive director of Irvine Ranch Conservancy, a nonprofit managing 50,000 acres of wildlands and parks in Orange County.
Although California regards the coastal cactus wren as a “species of special concern,” the U.S. Fish and Wildlife Service rejected a 1994 petition to list the bird under the federal Endangered Species Act. But biologists warn that the coastal cactus wren is in greater danger than another federally listed California bird, the California gnatcatcher, famous as “the bird that stopped a thousand bulldozers.” Cactus wrens are pickier about nesting habitat than are gnatcatchers, and there are fewer of them in more widely scattered populations, says Jonathan Atwood, director of the conservation biology program at Antioch University.
The coastal cactus wren’s range stretches from coastal Southern California to northwestern Baja California, and a significant percentage of the population lives within the region’s coastal sage preserves. By the time the preserves were established in the ’90s, coastal sage was already recognized as one of the most depleted plant communities in the United States because of urban development. The reserves were designed to link the remaining blocks of coastal sage scrub so that native wildlife could escape dangers such as fires and find food, shelter and mates. But the wren’s specific habitat was not emphasized when biologists designed the reserves, says Atwood, because the birds aren’t on the endangered species list. Some of the scientists who mapped vegetation for the preserves recognized cactus scrub as a part of coastal sage scrub; some did not. If the bird had been federally listed, they certainly would have paid more attention to including cholla and prickly pear.
Historically, coastal sage scrub burned once every 60 to 100 years; now, land managers are seeing fires every five to 15 years. The 1993 Laguna Beach fire burned three-quarters of what is now the Nature Reserve of Orange County’s coastal preserve. Thirteen years later, less than half of the cactus scrub in the coastal preserve had recovered enough to support wrens. Between 1999 and 2004, the bird’s population there fell nearly 70 percent.
The most recent fires, in October 2007, hit the area hard. More than two dozen fires, fueled by drought and driven by screaming Santa Ana winds, burned more than half a million acres of shrublands. The Witch Creek fire burned almost all of San Dieguito River Park. One-third of coastal cactus wrens counted in San Diego County from 1997 to 2002 were in the San Dieguito River watershed. Today, development has claimed 10 of 27 locations in the watershed where the bird was sighted, and the 2007 fires charred another 10. Christmas bird counts showed a dramatic fall in population in and around the river park: 45 cactus wrens were counted in 2006, and 17 in 2007.
In November, Kit Wilson, an independent GIS consultant and volunteer at San Dieguito, found that over the last four years, fully half of San Diego County’s coastal sage scrub burned. Using overlaid maps, he also discovered that 61,000 acres of chaparral and coastal scrub scorched by the 2007 fires had also burned in 2003. Such repeated fires harm native plants that are not adapted to this unnatural fire cycle, reducing the acreage and maturity of coastal cholla and prickly pear stands. They also clear the way for grass, bamboo and other alien plants, which burn more readily than native vegetation.
Fire officials are now realizing the importance of removing invasives and restoring native shrubs. As the fire-management strategy shifts from fighting fire to preventing it, some fire officials and land managers have come to see eye to eye. “They want restoration, we want restoration. They want no fire, we want no fire,” O’Connell says.
Irvine Ranch Conservancy is working with the Orange County Fire Authority to determine the top causes of ignition and create a fire prevention plan. Fire-prevention efforts may include cutting firebreaks, building cinderblock walls along highways to prevent cars from sparking wildfires, and improving surveillance in the preserves. Conservationists are also working to restore the cactus scrub; Jerre Ann Stallcup of the Conservation Biology Institute plans to plant cacti grown in nurseries or salvaged from developments to bridge isolated patches of scrub, giving the cactus wrens escape routes during wildfires.
Meanwhile, until the cactus scrub habitat fully recovers, Olson plans to install his fake cholla prototypes in seven choice locations. The next mating season is not until spring, but Olson wants to habituate the birds to the structures. The cacti are spray-painted green, with a little sand mixed in to give the birds a better grip. Olson mounts baffles on the poles at the base to keep bird-eating snakes from slithering up. As a final touch, he throws on some grass.
“If it doesn’t work,” he jokes, “we’re going to sell them to a Laguna Beach art gallery.”
The author is an independent journalist in San Francisco, California.
This article appeared in the print edition of the magazine with the headline Manufactured homes for the birds.
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