Male hummingbirds do 2 types of mating dance, the U and the shuttle. The former is a U-shaped rapid flight that starts high (as much as 50 feet) and swoops down to a low point where the female is located, and then up again. As the hummingbird rapidly decelerates at the bottom of the dive, the force reaches 9G - the maximum experienced by fighter pilots. Any more and the bird would disintegrate.
If this spectacular display attracts the female's attention (i.e. she continues to watch) he will switch to his shuttle dance, where he moves horizontally back and forth over a distance of a foot or so inches away from the female. This display is accompanied by loud buzzing, following the rhythm of acceleration and deceleration every second or so. Both these displays are also sometimes done as a warning, though usually in fragmentary form.
A few days ago I saw a U-dance, quite close to where I was trimming bushes. I could not see the female, and I thought perhaps my long-handled pruner had triggered his indignation. This occurred in their favorite arena for such displays, the bluff at the northwest corner of the sanctuary.
Today, working again with my pruner quite near this spot I suddenly heard the frantic rythmic buzzing of a shuttle dance, literally only a foot away! At first I again could not see the female: the dance was centered on a bare twig. But then, inches away, I saw the female, partly obscured by foliage. She was following the performance very closely. A few second later they both flew off.
Female hummingbirds can mate several times in a season: perhaps she already has a second nest prepared.
I will try to get video of a dance, but they have become quite uncommon compared to earlier years. In the meantime here is a video I took this afternoon, showing a female feeding from Salvia involucrata.
In the first frames you see the hummer darting about deciding where to feed next. Then she disappears for a few seconds while I try to see where she has moved. In the rest of the video she is feeding on S. involucrata, at one point clinging to a stem and even briefly bathing in a wet leaf. Notice also at one point she briefly backs off when a bee comes near.
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