Type: report

Article abstract: We surveyed for Least Bell's Vireo (Vireo bellii pusillus) along the San Luis Rey River, between College Boulevard in Oceanside and Interstate 15 in Fallbrook, California in 2008. We found 102 vireo territories, at least 48 of which were occupied by pairs. Four other vireos were transients. Vireos were concentrated in three clusters within the survey area. Only one vireo territory was found in the stretch of the river where giant reed (Arundo donax) was recently removed. Fourteen banded vireos were detected within the survey area. All positively identified banded vireos were originally banded along the San Luis Rey River.