The declines observed among known populations of Southwestern Willow Flycatcher in San Diego County indicate that flycatchers could benefit from a regional conservation strategy. Data on the current distribution and demography of the flycatcher within San Diego County, as well as identification of threats and stressors affecting the species, are essential components necessary to develop and implement a comprehensive approach to ensure the persistence of the species in San Diego County. To help fulfill the MSP goals and objectives established for the flycatcher, several tasks were initiated by USGS scientists, including surveys and demographic monitoring along the San Luis Rey River and other drainages in San Diego County to determine the current status of the flycatcher within the MSPA (Howell et al., 2022). The information obtained from surveys and monitoring between 2015 and 2023 (Howell and Kus, 2021; 2022; 2023; 2024) were combined with data from other ongoing studies (Houston et al., 2024; Howell and Kus, 2025), as well as all available data on historical occurrences (Unitt, 1987; Kus et al., 2003) to form the basis for the analyses for this project.

There are two parts to the recovery effort. The first part presents background information pertinent to recovery-oriented management of the flycatcher, outlines factors influencing flycatcher population dynamics, and summarizes the current knowledge regarding Southwestern Willow Flycatcher population status, trends, and demography (including productivity, survival, and dispersal) in San Diego County. The second part describes a potential science-based regional conservation approach, details site-specific management options to benefit Southwestern Willow Flycatchers, and ranks sites according to their potential to improve persistence of flycatcher populations. In particular, the second part provides managers with options for developing conservation projects to promote flycatcher recovery.