Distribution and Abundance of Least Bell’s Vireos (Vireo bellii pusillus), Southwestern Willow Flycatchers (Empidonax traillii extimus), and Coastal California Gnatcatchers (Polioptila californica californica) at the Santa Fe Dam, Los Angeles County, California—2022 Data Summary

Data Report 1171
Ecosystems Mission Area—Species Management Research Program
By:  and 

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Abstract

In 2022, we surveyed for Least Bell’s Vireos (Vireo bellii pusillus; vireo), Southwestern Willow Flycatchers (Empidonax traillii extimus; flycatcher), and Coastal California Gnatcatchers (Polioptila californica californica; gnatcatcher) in the Santa Fe Dam detention basin and along the San Gabriel River upstream from the Santa Fe Dam near Irwindale, California. Four vireo surveys were completed between April 21 and July 13, 2022; three flycatcher surveys were completed between May 18 and July 13, 2022; and four gnatcatcher surveys were completed between April 21 and July 13, 2022.

We detected seven territorial male vireos, including four that were paired and three with undetermined breeding status. We also detected one transient vireo. Two juvenile vireos were observed during surveys. Vireo territories were found in riparian scrub, willow (Salix spp.)-cottonwood (Populus spp.), and mixed willow habitat, with mixed willow the most commonly-recorded habitat type. Black willow (S. gooddingii) was the dominant plant species in most vireo territories.

We detected 10 transient flycatchers in riparian scrub (5 individuals), mixed willow (4 individuals), and non-native vegetation (1 individual). Black willow and mule fat (Baccharis salicifolia) were the predominant plant species in flycatcher locations.

We detected four territorial male gnatcatchers, two of which were paired and two of undetermined breeding status. We also detected one territorial female gnatcatcher. One juvenile gnatcatcher was observed during surveys. All gnatcatchers were detected in coastal sage scrub. The dominant shrub species at gnatcatcher locations were California sagebrush (Artemisia californica) and scale broom (Lepidospartum squamatum).

Suggested Citation

Lynn, S., and Kus, B.E., 2023, Distribution and abundance of Least Bell’s Vireos (Vireo bellii pusillus), Southwestern Willow Flycatchers (Empidonax traillii extimus), and Coastal California Gnatcatchers (Polioptila californica californica) at the Santa Fe Dam, Los Angeles County, California—2022 data summary: U.S. Geological Survey Data Report 1171, 12 p., https://doi.org/10.3133/dr1171.

ISSN: 2771-9448 (online)

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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), Southwestern Willow Flycatchers (Empidonax traillii extimus), and Coastal California Gnatcatchers (Polioptila californica californica) at the Santa Fe Dam, Los Angeles County, California—2022 data summary
Series title Data Report
Series number 1171
DOI 10.3133/dr1171
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Western Ecological Research Center
Description vi, 12 p.
Country United States
State California
County Los Angeles County
Other Geospatial Santa Fe Dam
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
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