Distribution, Abundance, and Breeding Activities of the Least Bell's Vireo at Marine Corps Base Camp Pendleton, California

Type: report

Article abstract: Surveys for the endangered Least Bell's Vireo (Vireo bellii pusillus) were conducted at Marine Corps Base Camp Pendleton (MCBCP or Base), California, between 3 April and 13 July 2017. Drainages containing riparian habitat suitable for vireos were surveyed two to four times. Six hundred and thirty-nine male vireos and 23 transient vireos were detected. Territorial vireos were detected on 19 out of the 23 drainages/sites surveyed. Ninety-two percent of all vireo territories occurred on the six most populated drainages, with the Santa Margarita River containing 65% of all territories on Base. Seventy-eight percent of male vireos were confirmed as paired.

Number of pages: 122

Authors: Lynn, Suellen; Allen, Lisa; Kus, Barbara;

Year: 2017

Purpose: The purpose of this study was to document the status of Least Bell's Vireo at Marine Corps Base Camp Pendleton in San Diego County, California. Specifically, our goals were to (1) determine the size and composition of the vireo population at the Base, (2) characterize habitat used by vireos, (3) band a subset of vireos to facilitate the estimation of vireo survivorship and movement, (4) assess the effects of the wildfires on vireos by measuring vireo territory density, survivorship, inter-annual movement, nest success, and productivity by intensively monitoring vireos within established nest monitoring sites that burned in October 2013 (sections of the Santa Margarita River and De Luz Creek) compared to reference sites in which vegetation had experienced little, if any, anthropogenic alteration in the past 15 years, and (5) document the vegetation structure and plant composition during the fourth breeding season post-fire in the sites that burned in October 2013 and the subsequent recovery of the vegetation at these sites. When combined with data from other years, these data will inform natural resource managers about the status of this endangered species at MCBCP, and guide modification of land use and management practices as appropriate to ensure the species’ continued existence.

Prepared for: Assistant Chief of Staff, Environmental Security U.S. Marine Corps Base Camp Pendleton;

Prepared by: U.S. Geological Survey, Western Ecological Research Center;

Keywords: endangered species; least Bell's Vireo; Marine Corps Base Camp Pendleton;

Species: Least Bell's vireo

Vegetation communities: riparian forest & scrub

Threats: Parasitism/disease