Distribution and abundance of Least Bell’s Vireos (Vireo bellii pusillus) and Southwestern Willow Flycatchers (Empidonax traillii extimus) at the Mojave River Dam, San Bernardino County, California—2024 data summary

Scarlett L. Howell; Barbara E. Kus

doi:10.3133/ofr20251025

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Distribution and abundance of Least Bell’s Vireos (Vireo bellii pusillus) and Southwestern Willow Flycatchers (Empidonax traillii extimus) at the Mojave River Dam, San Bernardino County, California—2024 data summary

Scarlett L. Howell·Barbara E. Kus

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Abstract

We surveyed for Least Bell’s Vireos ( Vireo bellii pusillus ; vireo) and Southwestern Willow Flycatchers ( Empidonax traillii extimus ; flycatcher) at the Mojave River Dam study area near Hesperia, California, in 2024. Four vireo surveys were completed between April 17 and July 2, 2024, and three flycatcher surveys were completed between May 23 and July 2, 2024. We detected three territorial male vireos, all of which were paired. No juveniles were observed during surveys. Vireo territories were reported in two habitat types: riparian scrub and willow-cottonwood. Red or arroyo willow ( Salix laevigata or lasiolepis ) was the dominant plant species in most vireo territories. No territorial or transient flycatchers were observed.

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Source-reported bounding extent: 34.31872800675019° to 34.370295162773715° latitude; -117.2768615020681° to -117.21059336313478° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Scarlett L. Howell, Barbara E. Kus. 2025-05-13. Distribution and abundance of Least Bell’s Vireos (Vireo bellii pusillus) and Southwestern Willow Flycatchers (Empidonax traillii extimus) at the Mojave River Dam, San Bernardino County, California—2024 data summary. https://doi.org/10.3133/ofr20251025

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