Assessing California’s mitigation guidelines for burrowing owls impacted by development

While burrowing owls (BUOW) have adapted to a variety of disturbed and developed sites, their presence in development areas results in conflicts between conservation and economic activity. Avoidance, minimization, and conservation measures are used when land development displaces and negatively impacts resident species. When avoidance of BUOW impacts is not feasible, the California Department of Fish and Wildlife (CDFW) recommends mitigation (required in compliance with the California Environmental Quality Act) through the use of disturbance buffers (setback distances) and burrow exclusion (passive relocation). In California, passive relocation is the most common mitigation strategy for BUOW affected by the impacts associated with renewable energy and other development projects, whereas active translocations are more often used elsewhere in North America.

The fates of BUOW relocated using passive and active methods have never been comparatively evaluated. A major research project, conducted in partnership with the U.S. Fish and Wildlife Service, is changing this by collecting data to evaluate these two relocation methods across four counties in southern California: Imperial, Riverside, San Bernardino, and San Diego. We used GPS satellite telemetry to track BUOW movements, mortality, and reproductive output in response to passive and active relocations (‘experimental’ groups), as compared to unrelocated BUOW (‘control’ group).

This project has also been designed to test new strategies intended to improve the overall efficacy of currently-used relocation protocols. A major consideration in animal relocation efforts is to find mechanisms to retain or “anchor” animals in suitable habitat at the release site. Since many species prefer to settle near individuals of the same species, translocated BUOW may not reoccupy suitable but empty habitat areas if there are no signs that members of their species inhabit the area. This project evaluates whether the addition of experimentally planted visual and acoustic stimuli improves BUOW post-translocation settlement.

Major funding for this project was provided by the California Energy Commission and CDFW. Renewable energy generation projects are a growing component of the State of California’s energy policy, providing reliable power while reducing the carbon footprint of energy generation.  Large-scale renewable energy projects (such as solar photovoltaic and wind power projects) are a rapid and increasing source of development throughout much of southern California. However, the location of planned facility expansions in BUOW habitat increases the risk to existing BUOW populations. Recommendations from this project are intended to help increase the efficacy of BUOW mitigation techniques and improve the conservation and management of BUOW.

Collaborators and funding sources include: U.S Fish and Wildlife Service, California Energy Commission, CDFW, Western Riverside County Regional Conservation Authority, Riverside County Parks, WRMSHCP Monitoring Program, Sonny Bono Salton Sea NWR, Imperial Irrigation District, Coachella Valley Conservation Commission, UCR-Palm Desert, Morongo Band of Mission Indians, Twenty-Nine Palms Band of Mission Indians, Cabazon Band of Mission Indians, Imperial Valley Community Foundation, Coachella Valley Water District, and many private consultants and project proponents.

Final Project Report for California Energy Commission, August 2020