Orange County Register

Cactus wrens flit in and out of dense thickets of prickly pear without getting jabbed by thorns. Humans, not so much.

That’s why volunteers answering the call of the Irvine Ranch Conservancy will be armed with gloves and tongs as they fan out across  10,000 acres of charred landscape over the next few weeks.

The volunteers hope to save the cactus wrens from local extinction. The birds’ numbers have plummeted in recent years in Orange County, largely due to excessive wildfire, which has destroyed the cactus patches they need to survive.

In the central part of the Nature Reserve of Orange County, for instance, the 2007 Santiago and Windy Ridge fires severely damaged more than 1,000 acres of the wren’s cactus scrub habitat, leaving fewer than 800 acres for the wrens to use for breeding.

“We’re trying to mitigate the impact of the Santiago Fire,” said Megan Lulow, a senior ecologist with the Irvine Ranch Conservancy. “We need to try to plant cactus over as much area as we can because so much habitat burned.”

Volunteers will plant a total fo 40 cactus patches across the central reserve, on land that was once part of the historic Irvine Ranch. Cactus also is being planted on the reserve’s coastal section.

Anyone can volunteer for the central reserve planting. And, Lulow says, don’t worry about the thorns.

“We use tongs to collect the pads, to harvest them, and to handle the pads,” she said.

Volunteers have already been collecting cactus pads around the reserve for transplantation, including a group of students from Sage Hill School in Newport Coast.  Now, volunteers are needed to continue the planting effort. 

The planting is being paid for in part with a $25,000 local assistance grant administered through the state Department of Fish and Game, with matching funds from the conservancy.

Though they’re not listed as endangered, coastal cactus wrens are considered a species of special concern in California. They are very local — the birds are not believed to fly long distances to relocate when their habitat burns — and a bit fussy.

In fact, they appear to have fairly rigid requirements even when the right cactus plants are present: cactus height, density and spacing all are important factors, it seems, in a cactus wren’s decision about where to breed.

Fortunately for the cactus planters, a well-known local scientist has spent years studying the key features of the best cactus wren breeding sites. Robb Hamilton has developed an index that can be used to evaluate cactus patches for their wren-drawing potential.

During walking surveys on the ranch in 2006, Hamilton noticed a sharp drop in cactus wren numbers along coastal Orange County. He believes the devastating Laguna Beach wildfire of 1993 is the reason: although the cactus is growing back, it is growing slowly, and much of it is not yet thick enough to appeal to cactus wrens.

Cactus is also being planted on the coastal reserve to fill in gaps that still remain from the Laguna fire, though volunteers are not being used in this case, said Kristine Preston, science program director at the Nature Reserve of Orange County.

Both the conservancy and the Nature Reserve of Orange County have tried a variety of experiments to boost cactus wren breeding.

Last year, the conservancy installed several structures meant to mimic cactus plants near known wren habitat. So far, however, the birds have not nested in the structures.

And in 2006, The Nature Reserve of Orange County captured 10 inland wrens and moved them to the Upper Newport Bay, in hopes they would recolonize an area their species had previously inhabited. As of August, Preston said, 11 cactus wrens still inhabit the area, including some descendants of the translocated birds, despite high levels of predation by Cooper’s hawks.

To volunteer for cactus planting in the central reserve, call Lulow at 714-508-4766 or email her at mlulow@irconservancy.org.

(Photo of Sage Hill School students helping ecologist Megan Lulow with cactus restoration project courtesy Wida Karim, Irvine Ranch Conservancy.)

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