I am up to my elbows in cactus, with a dozen or so inch-long spines poking out of each of my boots. Slowly and carefully I inch my way further into the spiny thicket. I keep my elbows high and my hands pulled in to my chest, as I lift my right leg up and over a low cluster of cactus pads. Spines scrape against the sides of my full-length snake chaps but they do not penetrate the Kevlar. I carefully wedge my right foot into a small bare space between two cactus pads and shift my weight to stabilize myself as I lift my left leg over and place my foot in a similarly precarious spot.
The branch of a leafy evergreen shrub with pink and white flowers brushes my arm as examine the section of the transect tape stretched alongside me. I use a long ruler to measure the length and height of the shrub and call out the measurements to my partner who is recording the data on a clipboard from a safer location outside the cactus. As I examine the thicket of cactus ahead of me, planning my next move, I smile as think about how strange this must look to the cyclists and hikers on the trail below.
So why have I voluntarily put myself inside a cactus patch? Some would say I’m crazy (which is somewhat true), but the real reason I’m here is because of an intrepid little bird called the San Diego cactus wren. These birds are endemic to the coastal areas of Southern California and are considered Species of Special Concern in California. Recently, they have been declining due to habitat loss as a result of urbanization, frequent wildfires and invasive species. In an effort to prevent this species from reaching the brink of extinction, habitat restoration efforts that involve planting thousands of cacti have been implemented throughout San Diego County.
We know that cactus wrens rely on cactus for nesting because that is where we find cactus wren nests. However, we have very little knowledge of what other habitat features cactus wrens prefer and/or avoid when choosing their nest sites. There are many places with large, mature cacti that cactus wrens do not inhabit, which caused us to wonder: if we just plant cactus, is it enough? Or do we need to be doing something else (i.e. planting other native shrubs or removing invasive annuals) to make the restored habitat suitable for nesting. To answer these questions, I am visiting both cactus wren nest sites and “control” sites (areas where there is plenty of cactus but no cactus wrens) and measuring a slew of habitat variables including shrub cover, shrub species, shrub height, cactus height, cover of annual forbs, distance from the nest to the nearest shrub, and many more. Often, collecting this data involves having to literally “get into” some dense cactus stands.
And so I find myself elbow deep in spines, seeing the world from the perspective of a cactus wren. It’s a prickly job but rewarding as well. By comparing the habitat characteristics of areas with cactus wren nests to areas without, we are learning what cactus wrens prefer and what they avoid. For example, it appears that the wrens prefer to build their nests in a cactus that is taller than the vegetation surrounding it, and they tend to avoid areas covered with invasive annual plants. Discoveries like these are exciting to me because this information can be incorporated in to restoration and management plans that will ensure successful conservation of this species.
Sara Motheral, Senior Research Technician, Applied Plant Ecology.