The Anna's Hummingbird is a year round resident of San Jose, California. They are best seen feeding on a variety of flowers not at a hummingbird feeder. These feeders seems to bring out only these tiny birds aggressive nature but little of the great diversity of behaviors they exhibit
For example, I was picking raspberries one morning and heard the distinctive "chip" of a hummingbird. I looked up and there was a female hummingbird hovering about two feet across the row of raspberries from me at eye level. It proceeded to dip and "chip" several times until I moved several feet down the row of raspberries and she began feeding on the raspberry flowers. She just was ordering me to retreat to a safe distance while she fed.