Venting is done to tell the difference between a young male and female white duck. Venting is the practice of gently squeezing ducklings until a small bit of fecal matter is expelled. This forces the cloaca to open slightly and expose the duck's genitalia.
Hatchlings are difficult to sex even with the venting method. Mature ducks are the easiest to sex. Adult male ducks have a curled tail feather called a drake feather. Their vocalizations are weaker than the female duck's. Male ducks also have one black feather in the back under their wings. It is very easy to determine the adult female's gender with the venting method.