A stand of mature cactus in Filiorum Reserve

Conservancy Helps to Enhance Cactus Wren Habitat

Date: December 21, 2018
The coastal cactus wren is one of the rarest and most imperiled wildlife residents in the coastal southern California region, including the Palos Verdes Nature Preserve. As its name implies, this uniquely adapted inhabitant thrives among cactus-dominated patches of coastal sage scrub, living and nesting within dense stands of native prickly pear and coastal cholla cactus. Cactus wren populations are steeply declining across their southern California range because of wildfires, urbanization, invasion by non-native plants, drought and a number of other factors. The State of California has recognized this decline by designating the cactus wren a “Species of Special Concern.” This status provides specific protections under state law. Palos Verdes’ coastal cactus wrens have not escaped this decline, with observed breeding territories dropping to all-time lows in 2018. Despite all of the challenges they face, Palos Verdes’ small population has found a way to persist despite a host of daunting challenges.

In 2018 both Conservancy-contracted biologists from Cooper Ecological Monitoring, Inc. and the Conservancy’s Citizen Science Cactus Wren Monitoring Program monitored cactus wren populations in the Palos Verdes Nature Preserve. Both surveys found cactus wrens, but in fewer reserves and in lower abundance than in previous survey years. Cooper identified five potential breeding territories throughout the areas surveyed in the Preserve and the Conservancy’s citizen scientists located a handful of active nests. Both teams observed cactus wrens exclusively in the areas that provided only the highest-quality habitat, those with large expanses of mature cactus plants.

The Conservancy has outlined measures needed to conduct a targeted habitat enhancement to help the cactus wren. As land managers, the Conservancy is the organization best positioned to meet or mitigate habitat challenges negatively impacting cactus wrens’ breeding potential and survival. In collaboration with the contracted biologist and wildlife agencies, the Conservancy has determined several adaptive management activities to improve the viability of the Palos Verdes cactus wren population. Recommended activities will focus on enhancing and protecting mature cactus stands, giving priority to those that have recently supported nesting. Invasive non-native shrubs (especially Acacia) will be removed from cactus-rich areas, new cactus plantings will be installed and foraging habitat (bare ground) surrounding cactus patches will be created. These habitat enhancement plans may be just what the cactus wrens need for a successful 2019 breeding season. To assist the project and help save our local cactus wren population, become a citizen scientist! Contact the Conservancy’s Stewardship Associate, Josh Weinik, at jweinik@pvplc.org.