From the hummingbird exhibit at the Arizona-Sonora Desert Museum: 

Courtship and Mating

The male attracts a female with flashes of its iridescent plumage, a spectacular courtship dive, or a thin scratchy song. The birds must then overcome their natural aggressiveness long enough to mate. Their mating behaviors are not well known. After a brief encounter, each bird may court and mate with a number of others during one nesting cycle.

I find it amusing that the propagation of a species depends upon the male and female taking just enough time to stop fighting so they can have sex.