(noun) The specialized wing of a penguin. Very few birds have true flippers, but these wings are flat and broad with a tapered shape that facilitates powerful, agile swimming, and because of that severe adaptation, penguins cannot fly. Unlike other swimming birds that use their feet and legs for primary underwater propulsion, penguins use their wings for propulsion and the feet and legs are used principally for directional changes.
Unlike the wings of birds that fly, penguin flippers can only be moved from the shoulder and the elbow and wrist are almost completely fused. This gives the flipper more power in the water and allows faster swimming and movements such as porpoising. Penguin flippers do have feathers, but instead of primary and secondary feathers that are critical for flight, the feathers on a flipper are smaller and more densely packed to help streamline the wing and provide insulation. Flippers also typically have countershading coloration that is light above and dark below to help camouflage the bird in the water.
In addition to being essential for swimming, flippers are also used for bird communication. Penguins will pat one anothers' flippers as part of their courtship behavior, and flipper slapping can be used to show aggression. For locomotion on land, flippers can help penguins propel themselves when tobogganing on the ice.
While penguins are the only birds that have true flippers, other pelagic birds that spend a good deal of time swimming, such as puffins, murres and auks, have some flipper-like characteristics to their wings, but to a lesser degree.
Photo – King Penguin Grooming Flipper © Vicky Brock