Australian Pink-eared Duck feeding on plankton

The pink-eared duck (Malacorhynchus membranaceus, 红耳鸭) is a species of duck endemic to Australia. They mainly feed on plankton, but also eat crustaceans, mollusks and insects. Their bill is well designed for straining minute organisms, with pliable mandibular flaps that channel water in a manner that allow the ducks to filter algae and other plankton efficiently. They also feed by vortexing, in which two ducks spin about a central point with the head of one opposite the tail of the other, concentrating food in a gyrating water column. -- wikipedia