(genus Tachyeres), any of four species of heavily built, big-billed sea ducks of southernmost South America and the Falkland Islands. The bird is named for its habit of running across the water with wings thrashing like a paddle-wheel steamboat. Of the four species, T. pteneres, T. brachypterus, and T. leucocephalus are flightless and a bit larger than the mallard-size flying steamer duck, T. patachonicus. Steamer ducks are classified in a tribe of their own, Tachyerini, family Anatidae (order Anseriformes).