Aha! Finally caught some photos of a chestnut-backed chickadee.
This happened by chance.
I was standing with the camera on our patio observing some bees on the California figwort.
And suddenly, with a great flapping of wings, this chickadee landed on a branch of a large potted rosebush.
Some of the long branches of the figwort are pushing through the rosebush.
You can see the distinctive little figwort buds here center right.
It was in the very late afternoon, and I think the chickadee was after tiny insects in the rosebush.
By the look of the feathers I think this is a young chickadee.
I'm so thrilled to have had this encounter, because I often hear the chestnut-backed chickadees singing and chirping in the trees around the garden, but rarely actually see them.