The stiff-tailed ducks are part of the Oxyurinae subfamily of ducks. All have, as their name implies, long stiff tail feathers, which are erect when the bird is at rest. All have relatively large swollen bills.
These are freshwater diving ducks. Their legs are set far back, making them awkward on land, so they rarely leave the water.
Their unusual displays involve drumming noises from inflatable throat-sacs, head throwing, and erecting short crests.
Feather sequences are complicated, and it is hard to tell how old one of these ducks is. Feathers are vital for survival because of this animals tendency to spend time in the water. Without feathers this duck would die of hypothermia because it couldn't regulate its body temperature.