I think that's a female Anna's hummer. I had a male stay at my yard since last summer. His name is Rocket, and chases all other males away and then goes absolutely nuts when a female shows up. Seen him pull of the chirp dive twice now. He helicopters up about 50 feet and then nose dives down about 45 mph and then loops up at the bottom of the dive. The creates the tail feathers to make a really loud chirp. This was only proven in the late 90's which is hard to believe.