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.
Thanks Bryan for this very interest article about the coastal cactus wren and the cacti they depend on. I was at the Safari Park (WAP as it was know at that time) about 6 months after the fire and was surprised at seeing how close it came to all the animals.
To know that it could happen again, at any time, must push you all harder to make sure there are enough areas that these birds are in to ensure the species survives. It takes a strong person to work it those conditions and with prickly cacti but the birds all appreciate it.
Very interesting post and thanks for all your efforts to restore habitat for these little wrens. It sounds like tough but rewarding work!
Great story and glad someone notices things like coatal cactus Wrens.
I’m curious as to why you didn’t simply out plant the Prickly Pear Pads in the areas to be colonized but rather chose to put them in what looks to be two gallon degradable pots. Was it because you didn’t have a site location yet ?
Also, I have way back in the past rescued several Coastal Cholla specimans by collecting as many of the jointed sections in the way of development back in the late 1970s near Santee Lakes. I have written about this on my environment blog. The area colonized is well over an acre and the Cholla colonies extremely mature. This was done in 1980 long before the Sky Ranch Housing development went in. Before I moved over here to Europe in Sweden, I took a visit there just before that development construction started. Someone had put sensitive Conservation area tape around this acreage. To my surprize there were Cactus Wren nest in several mature cholla. I also relocated Coast Barrel Cactus and some Prickly Pear from a lower Indian encampment on Rattlesnake mountain.
I was excited about the Wrens as I had never seen them before growing up in the late 50s and thru the 60s on Rattlesnake Mountain. Best Coast Cholla samples to find will be there at that location and many of the southern facing slopes on the north side of Mission Valley.
Good luck – Kevin
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Thanks for the comments and insights, Kevin. We propagate the cacti in a shadehouse for a couple reasons. One reason is that the cacti grow faster under shadehouse conditions than planting directly into the restoration plots. This is important, because coastal cactus wrens require cacti that are at least 3 feet tall to build their nests. So, if we are able to promote faster growth, it will speed up recovery efforts. We generally propagate the cacti for about 6 months before planting them in the wild.
The second reason we propagate cacti is to reduce herbivory by wood rats, coyotes, mule deer, rabbits, and other wildlife right after planting. We have found extremely high herbivory rates on small cactus pads planted directly into the restoration plots. Large cacti are also browsed, but not as heavily, and they recover more quickly!
Thanks interesting because I’ve never had those problems in the past. The pads you are using also look bigger than what I had collected around the native American village site. But even when I planted coastal Cholla I never had any herbivore problem. I never used shade cloth when out planting, but I do use nurse plants like Cal Buckwheat etc.
I would imagine the faster growth allows for wider space in between the needle bundles. The Bashan Foundation down in La Paz Baja California realized something similar when they innoculated a specific type of benefical bacteria to the Cardon cactus seedlings. They grew very faster, in fact so fast that they had less needles which were detrimental to outplanting and rodent feasting was made easier with the less needles.
You are correct on the height requirements. The Wrens in the Coastal Cholla on Rattlesnake Mountain in El Cajon were 3+ feet before they appeared. Of course so many things have changed in the wildlife world. I’ve noticed many things don’t behave as they once did. Maybe the fires removing the vegetation created further desparation for the animals to chance the Cacti.
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Congratulations to all involved in making the huge effort to restore the habitat and help the little cactus wren population survive. It is only those that understand biodiversity and the importance of all flora and fauna, and taking action to save habitats, that are making a real difference.
Nice blog on cactus. I have thought they would be helpful to wild animals. Great …