Distribution, Abundance, and Breeding Activities of the Southwestern Willow Flycatcher at Marine Corps Base Camp Pendleton, California—2022 Annual Report
In 2022, surveys for the endangered Southwestern Willow Flycatcher at Marine Corps Base Camp Pendleton, California, focused on all historically occupied riparian habitats, with no surveys conducted in non-core areas. Researchers observed eight transient flycatchers of unknown subspecies across three of five surveyed drainages, in mixed willow, riparian scrub, and upland scrub habitats, often amid exotic vegetation such as poison hemlock. No resident Southwestern Willow Flycatchers were detected on the Base for the second time since monitoring began in 2000, reflecting broader statewide declines. The single uniquely banded female present in 2021 did not return, and no transients were banded. Historical data indicate adult annual survival of 60±3 percent and first-year survival of 20±3 percent, while a conspecific attraction study using automated playback units continued through 2022 with no flycatcher responses.
Howell, S.L., and Kus, B.E., 2024, Distribution, abundance, and breeding activities of the Southwestern Willow Flycatcher at Marine Corps Base Camp Pendleton, California—2022 annual report: U.S. Geological Survey Open-File Report 2023–1080, 27 p., https://doi.org/10.3133/ofr20231080.