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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—2021 Data Summary

Data Report 1149
By:  and 
https://doi.org/10.3133/dr1149

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Executive Summary

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 2021. Four vireo surveys were conducted between April 16 and July 16, 2021, and three flycatcher surveys were conducted between May 27 and July 16, 2021.

We detected four territorial male vireos, including two that were paired and two with undetermined breeding status. No juveniles were observed during surveys. Vireo territories were found in three habitat types: (1) riparian scrub, (2) willow-cottonwood, and (3) willow-sycamore, with willow-cottonwood being the most commonly recorded habitat type. Red or arroyo willow (Salix laevigata or lasiolepis) was the dominant plant species in most vireo territories.

No territorial or transient flycatchers were observed.

Suggested Citation

Howell, S.L., and Kus, B.E., 2022, 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—2021 Data Summary: U.S. Geological Survey Data Report 1149, 7 p., https://doi.org/10.3133/dr1149.

ISSN: 2771-9448 (online)

Study Area

Table of Contents

  • Acknowledgments  
  • Executive Summary  
  • Introduction  
  • Methods  
  • Results  
  • Summary  
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title 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—2021 Data summary
Series title Data Report
Series number 1149
DOI 10.3133/dr1149
Year Published 2022
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Western Ecological Research Center
Description vi, 7 p.
Country United States
State California
County San Bernardino County
Other Geospatial Mojave River Dam
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details