Barred owls (Strix varia) have reached high densities within the range of the northern spotted owl (S. occidentalis caurina) and are rapidly increasing in number within the range of the California spotted owl (S. o. occidentalis). Encroaching populations of barred owls pose a significant competitive threat to the viability of both spotted owl subspecies in California. In response, the Director of the California Department of Fish and Wildlife (CDFW) convened the California Barred Owl Science Team (BOST) to identify and address the threat posed by barred owls to spotted owls in California. BOST is composed of subject matter scientists with a goal to provide objective scientific review and recommendations to CDFW to promote the recovery and conservation of spotted owls in California.

In this document, BOST identifies, describes, and prioritizes key research needs for barred owls that have the potential to benefit the conservation of spotted owls in California. Key research needs were identified from multiple in-person and remote meetings of BOST, with considerable input from attending representatives from state and federal natural resource agencies. BOST and liaisons recognize that periodic updates of this document will likely be required as more is learned about the ecology of barred owls in California and research needs and priorities evolve.

Research that BOST deemed the most likely to provide a rigorous scientific basis for reducing barred owl populations included experimental removals, along with ecological studies expected to generate information that would provide avenues for the effective management of barred owls. Other high priority research needs include research using biological samples obtained during experimental removals to better understand the ecology of barred owls and the threats they pose to spotted owls and associated wildlife. We conclude the document with a discussion of how projects are related to the State Wildlife Action Plan. In Appendix I, we discuss considerations for maximizing the success of proposed removal experiments and ecological research on barred owls.