[1] Hays, L. 2006. Personal communication with Loren Hays, U.S. Fish and Wildlife Service, Carlsbad, CA, January 17, 2006.
[2] Joregensen, P. 2005. Bell’s vireo population survey and cowbird trapping report for Anza-Borrego Desert State Park (Vireo bellii pusillus) and Picacho State Recreation Area (Vireo bellii pusillus) for the 2004 Breeding Season. California State Parks, Colorado Desert District, Borrego Springs, CA.
[3] Jorgensen, P. 2005. Personal communication with Paul Jorgenson, California State Parks, Colorado Desert District, November 7, 2005.
[4] Kus, B. 2001. Least Bell’s Vireo Surveys and Nest Monitoring at Anza Borrego Desert State Park in 2000: Final Report. U.S. Geological Survey, Western Ecological Research Center, San Diego Field Station.
[5] Kus, B.E. and M.J. Whitfield. 2005. Parasitism, productivity, and population growth: response of least Bell's vireos (Vireo bellii extimus) and southwestern willow flycatchers (Empidonax traillii extimus) to cowbird (Molothrus spp.) control. Ornithological Monographs 57:16-27.
[6] Kus, B. 2006. Least bell's vireo population trend at Camp Pendleton, 1981-2005. Spreadsheet provided by Barbara Kus, USGS Western Ecological Research Center, San Diego, CA, January 12, 2006.
[7] Pike, J., D. Pellegrini, L. Hays, and R. Zembal. 2005. Least Bell's Vireos and Southwestern Willow Flycatchers in the Prado Basin of the Santa Ana River Watershed, CA. Unpublished report prepared by the Orange County Water District and U.S. Fish and Wildlife Service.