Anna's Hummingbird working though the blossoms on a cherry tree in the Washington Park Arboretum. Then she stopped, and perched, sticking out her tongue from time to time. (I think she was cleaning the pollen off her beak). I noticed more movement in the blossoms: one, two, three other female hummingbirds going from flower to flower. Two of the females flew away, a subadult male and an adult male flew in, and they all kept eating and leaving each other alone - at least for a while.
Then the adult male started chirping and doing loop-de-loop territorial displays, right over the tree. This did not appear to have any effect on the three other hummingbirds peacefully guzzling nectar, and after a while he stopped, drank some nectar from the flowers, and then flew to a nearby tree, where he let off volleys of chirps - what I call the squeaky bicycle noise. And the others kept eating.