Arctic Junco, we have those here in winter. I'm thinking it's something else because a Junco should be way north of me up here in Montana.

ETA: https://www.allaboutbirds.org/guide/Dark-eyed_Junco/overview

We have them in SLO too, very fun to watch...

I used the Merlin app and that was its guess.

It came around the last couple of years. It's very tiny.