Eventually I spotted a few insects visiting the flowers...and one of them was a nice surprise for me:
Although it might look like a moth at first because of its overall brown coloration, note the knobs (or swellings) at the tips of the antennae, indicative of a butterfly.
This is a fast-moving species, and I didn't get great pictures. But here's a slightly different angle:
This is a Propertius Duskywing (Erynnis propertius). [Propertius was a Latin poet, but I can't find an explanation for why this butterfly was named after him.] Its caterpillars feed on oaks, many of which surrounded this grassland, so this was good habitat for this species.
I haven't spent much time around oaks since moving to California, so this is my first duskywing sighting. It brought back memories of scrub oak habitat on Cape Cod...and the same feelings of frustration watching duskywings dashing around, hardly ever stopping, making it difficult to see their field marks and to photograph them. As soon as I saw the way it flew, I knew it was a duskywing, and that it was going to be challenging.
Duskywings are territorial and this one was true to form. It chased other butterflies that tried to nectar on nearby flowers. Here's a shot of the duskywing after it dove at a lady (the butterfly at the lower right):
It will be fun to go back and try for better views.