Out of Penguin, Ostrich, Emu, Duck, and Kiwi; only Duck is a birds that can fly.
Ducks have small wings. They must flap their wings fast (about 10 times per second) to keep their relatively large bodies airborne.
With this wing shape and rapid wing beat, most ducks can fly at 80 km per hour!
Penguin, Ostrich, Emu, Kiwi can't fly. But, few species of Ducks can fly.