This individual shows some features suggestive of a female "Pink-sided Junco" (Junco hyemalis mearnsi) but has received mixed reviews from experts.
The status of Pink-sided Junco in Northern California remains murky because of it close resemblance to some female "Oregon Juncos" (Junco hyemalis [oreganus Group]). Pink-sided intergrades with Oregon (J. h. montanus) in central Idaho and perhaps this bird pertains to such a hybrid. Montanus is widespread in California in winter, but mearnsi is uncommon primarily in interior San Diego and Imperial Counties.
Opinions on the subspecific identity of the above bird are welcome.
Digiscoped from a distance of 250 m with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA |hand-held (no adapter).