Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey Flood Risk Management Project Area in San Diego County, California: Breeding Activities and Habitat Use—2023 Annual Report

Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey Flood Risk Management Project Area in San Diego County, California: Breeding Activities and Habitat Use—2023 Annual Report

In 2023, surveys for Southwestern Willow Flycatchers detected four transient individuals and no residents. Vegetation sampling of 516 points and 90 nest/territory plots showed that vireos selected territories with distinct foliage structure, favoring mid- and upper-canopy cover in the Channel and low- to mid-canopy cover in Upper Pond, while nest-site selection within territories was largely random, highlighting the species’ habitat preferences and response to ongoing vegetation management.

Houston, A., Allen, L.D., Mendia, S.M., and Kus, B.E., 2024, Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey Flood Risk Management Project Area in San Diego County, California: Breeding activities and habitat use—2023 Annual report: U.S. Geological Survey Open-File Report 2024–1040, 77 p., https://doi.org/10.3133/ofr20241040.