Cactus Wrens Rise from the Ashes

Coastal cactus wrens build their nests in large prickly pear cactus. When cacti are killed by land clearing or wildfires, wrens have nowhere to nest.

After the 2007 Witch Creek Fire, which burned through the San Diego Zoo Safari Park and surrounding San Pasqual Valley, the outlook seemed grim for local populations of coastal cactus wrens. With populations already rapidly declining throughout Southern California, we all wondered if the fire, which heavily damaged critical nesting areas, was going to be one of the last chapters in an all-too-familiar story of species loss. A survey for coastal cactus wrens within the Safari Park Biodiversity Preserve shortly after the fire turned up only 10 pairs, further suggesting the population here was in a precarious position.

Even as the land smoldered, we began developing habitat restoration plans to help speed up recovery of native habitat. We focused on two critical coastal cactus wren needs: prickly pear cacti, which the birds need to nest, and native shrubs such as elderberry, buckwheat, and California sagebrush. Our goal was to enhance 45 acres (18 hectares) of habitat to support the recovery of wren populations and ensure the long-term survival of the species here in the San Pasqual Valley.

We have propagated thousands of native prickly pear cacti to support habitat restoration for cactus wrens.

Efforts began in 2008 and involved propagating and planting thousands of cacti and native shrubs across difficult, rugged terrain. Sometimes, the last four years seem like a blur of hard work, hot temperatures, sweat, blood (cactus spines hurt!), and more work. The effort, led by Sara Motheral and Colleen Wisinski, has been nothing short of amazing. We are nearing our goal! This year, we will complete the habitat enhancement of the 45 acres. Even more exciting is the fact that wren populations are rebounding—it is hard not to see or hear wrens calling while walking in the Safari Park Preserve.

Colleen Wisinski monitors a cactus wren nest, checking for eggs, at the Safari Park’s Biodiversity Preserve.

Even as we approach one milestone in the project, we are already expanding our efforts beyond the Preserve and have begun developing habitat restoration plans throughout San Pasqual Valley to connect isolated populations of wrens and create new habitat patches. It is only a matter of time before the next wildfire happens, and the long-term survival of the wrens depends on having high-quality habitat within the Preserve and throughout San Pasqual Valley.

To this end, we are already propagating cacti to enhance an additional 50 acres (20 hectares) of habitat throughout San Pasqual Valley and utilizing advanced technology such as Geographic Information Systems, spatial analysis, and computer modeling and simulations to help us determine high-priority locations for habitat restoration efforts to maximize the probability of success. No rest for the weary!

Bryan Endress is the director of Applied Plant Ecology for the San Diego Zoo Institute for Conservation Research.