Canon EOS R5 with Canon 100-500 mm L-series lens with 1.4x Teleconverter; 700 mm; ISO-1000; f/11; 1/500 sec.
This page is for the Bronze Mannikin (Spermestes cucullata). The identification was particularly tricky on this one, and could still be wrong. I had it down to a juvenile Bronze Mannikin or a juvenile Scaly-breasted Munia. The juveniles look identical. I did some more research and both are likely escaped exotics from the pet trade (Bronze Mannikin from Africa and Scaly-breasted Munia from Asia), both are occasionally found in southern California with the Munia a bit more common and a nearby park having the greatest chance of sighting the Mannikin. After comparison to many images found online and the research mentioned above, I and two other people settled on the Bronze Mannikin.