Young birds tend to use their feet a lot more in the early days until they develop cordination in their wings and learn how to control speed and direction. They extend their feet on landings and to assist in feeding. Once they learn to control their start and stop better, they'll rely on the pinpoint accuracy that the wings will provide. Eventually the legs become less important in their movement to the point they rarely need to be extended, except for emergency and fierce battles.
This young bird was coming in for a landing, being fully prepared to grasp hold of the lower petal of the flower. It's sharp little talons would pierce through the petals and provide enough traction for it to gain hold and feed for a few seconds in each flower.
Once they mature, they will tuck in those feet to be rarely shown, and start to choose flowers that require a little less monkey work to get the nectar.
Juvenile Ruby-throat hummingbird. N.E. of Edmonton, Alberta, Canada. August 2017