Today I learned: Flamingos feed with their heads upside down and that their beaks are adapted for this purpose.
This essay on flamingo feeding from Stanford explains:
In most birds a smaller lower beak works against a larger upper one. In flamingos this is reversed; the lower bill is much larger and stronger, and the fat tongue runs within the bill's deep central groove. To complete the jaw reversal, unlike other birds (and mammals) the upper jaw is not rigidly fixed to the skull. Consequently, with the bird's head upside down during feeding the upper bill moves up and down, permitting the flamingo's jaws to work 'normally.' Part of the flamingo's filter feeding is accomplished simply by swinging the head back and forth and letting the water flow through the bill. The tongue also can be used as a pump to pass water through the bill's strainer more efficiently. It moves quickly fore and aft in its groove, sucking water in through the filter as it pulls backward, and expelling it from the beak as it pushes forward. The tongue may repeat its cycle up to four times a second.
This neat underwater video from the San Diego Zoo shows this "filter feeding" in action. Wow!
screengrab via San Diego Zoo