Partnering with the US Fish and Wildlife Service (USFWS), the WFVZ has conducted Least Bell’s Vireo (Vireo bellii pusillus) (LBVI) point count surveys at numerous points along the Santa Clara River for the past five years, with 2025 being the last season (for now!). The LBVI is an endangered bird that migrates from Central America up to Southern California during the breeding season. It mainly breeds along the Santa Clara River and was listed as endangered in the 1980s due to habitat loss and nest parasitism by Brown-headed Cowbirds (Molothrus ater). Restored areas of the Santa Clara River provide quality habitat as invasive giant reed (Arundo donax; “Arundo”), which frequently dominates parts of the river, is unable to provide suitable nesting habitat for LBVIs. The data collected from the point count surveys will be used to study LBVI population trends over the years and evaluate if this endangered species is recovering well from habitat loss and Brown-headed Cowbird parasitism. Through this project, the USFWS will be able to inform future management decisions based on the data the WFVZ helped collect!
Male Least Bells’ Vireo (Vireo bellii pusillus) feeding fledglings at our research site, Cienega Springs Ecological Reserve in Fillmore, California. Video credit to Lindsay Rose.