In our Sunnyvale garden, there is always one, and only one, dominant male hummingbird. He tries to keep every other hummingbird away from the feeder with one exception: During breeding season, the male allows some females to feed.
When you are in the garden, often you will hear a high-pitched chirping sound. This is the sound of a male dive. The male soars up to 50 feet, then dives in a steep parabolic arc. The sound you hear is not his voice but the sound of his wings. He is showing off to the females.