I don't have Rouen ducks, but from what i know Shadow is a girl.
Six weeks old? You should definitely be able to voice-sex them: Take one of them in your hands and start to walk away from the group. The duck won't like it and will start to protest. If it quaxs or quacks it is a girl.
Plumage in domestic ducks is usually not really an indicator for the gender. Most domestic breeds have been "watered" down. For example my "Buff Orpington" drake: He should have really dark feathers on his head - he has not. A little darker but i have a female with even darker feathers.
Six weeks old? You should definitely be able to voice-sex them: Take one of them in your hands and start to walk away from the group. The duck won't like it and will start to protest. If it quaxs or quacks it is a girl.
Plumage in domestic ducks is usually not really an indicator for the gender. Most domestic breeds have been "watered" down. For example my "Buff Orpington" drake: He should have really dark feathers on his head - he has not. A little darker but i have a female with even darker feathers.