Hummingbirds have the ability to fly up and down, and forward and backwards because they have a rotator cuff (a supporting and strengthening structure of the joint) which allows them to move their wings in a figure eight motion. In contrast, other birds do not have rotator cuff and can only fly up and down.
May 31 2004, 10:13 PM
They do this when feeding on nectar from flowers.
They fly backwards so that they can remove their beak (or bill, whatever you call it on a hummingbird) from the flower while in flight.