There were a bunch of these flitting around a mostly dry stream bed running through oak woodland. Somewhat tentative ID given that MPG doesn't have a complete set of photos for this genus in CA, but it's a good match for pics from BG and PNW Moths, particularly given the light-bordered reniform spot: http://bugguide.net/node/view/101591/bgimage http://pnwmoths.biol.wwu.edu/browse/family-noctuidae/subfamily-amphipyrinae/tribe-stiriini/annaphila/annaphila-decia/