Harteman Wildfowl, presented by Jan Harteman
The videoclip below shows the practise of vent sexing. Vent sexing involves opening up the duck's anal vent (called a cloaca) slightly, to see if the duck has a penis, which indicates that the duck is a drake (male). Venting normally happens only when species don't show sexual dimorphism; mainly geese, swans and juvenile ducks. Or, in this case, for educational purpose. Please be aware that venting is not easy and it may harm the bird if not done correctly. We recommend that you are taught by someone experienced before trying this yourself as there are optimal times for many species and you may get inaccurate results.
Above: Vent sexing a duck. Footage by Jurre Brenders