Fun sightings at Oaks Bottom. But, I wouldn't necessarily consider Anna's nesting in early February a sign of spring. They nest throughout fall and winter too: I've seen one sitting on an egg in San Francisco on New Year's Day.
I think they may have once been endemic to southern California in the US and Baja California Norte in Mexico. As they spread north with the planting of exotic vegetation and the provisioning of feeders--and maybe a little global warming--they seem to have retained a sub-tropical breeding pattern. That is, they breed mostly through the rainy season and knock off in summer when there is probably less nectar available in the wild. They feed nestlings mostly insects, but probably always need at least some high-sugar, high-fat resources to maintain their incredible energy outputs.