We were very fortunate to have this bird come down from the hillside and pose nearby. San Mateo County has fewer than 10 previous records of this species which ranges marginally into Bay Area foothills. This individual was found by Alvaro Jaramillo last Sunday, 31 May 2020. One or two Black-chinned Sparrows were seen at this location off and on between 6 June and 13 July 2018. I believe it is likely that this is one of the same birds returning.