When will you be able to tell a drake rouen duck from a hen rouen duck by color?

You can typically distinguish a drake Rouen duck from a hen by color when they are around 5 to 6 months old. Male Rouen ducks have a distinctive green head with a white ring around their neck, while females have a more mottled brown appearance with a less vibrant coloration. Before this age, both sexes have similar plumage, making it difficult to tell them apart by color alone.