Did you ever see a hummingbird catching small gnats from a swarm in the air? I once did. At first I had the impression that the hummingbird was doing some kind of dance, bobbing up, down, forward, back, and sideways. Looking more closely, I saw that it was flying around a swarm of gnats and snatching them one by one out of the air. For the bird, it may be an important source of protein, and a welcome break from a diet of nectar.