The California Department of Transportation (Caltrans) Lonestar Mitigation Site (Lonestar) in San Diego County is just one example of the many collaborative efforts between Caltrans District 11 and various agencies and organizations. Caltrans has worked with the San Diego Zoo Institute for Conservation Research (ICR), U.S. Fish and Wildlife Service (USFWS), and the California Department of Fish and Wildlife at Lonestar since 2011 to maintain, monitor, and gain insight on methods to support the western burrowing owls (Athene cunicularia hypugaea). After restoration of the Lonestar Mitigation Site in 2012, including installation of 50 artificial owl burrows, burrowing owls moved into the site and breeding success has been monitored with over one hundred burrowing owl fledglings banded to track individuals over time. Caltrans has also worked with the ICR, USFWS, and the Conservation Biology Institute to reintroduce federally endangered Quino checkerspot butterfly (Euphydryas editha quino) larvae to enhanced habitat containing both native host and nectar plant species at Lonestar in 2017. Both larval and adult Quino checkerspot butterflies were recorded at the site in 2018 and 2019. It is through continued collaborations with other agencies and organizations that Caltrans can ensure success and long-term health of mitigation sites, such as Lonestar.