I have six ducks, 5 are Rouen and 1 is a Cayuga. I have one drake (a Rouen), the rest are hens. They are all between 6 and 8 years old. One of the Rouen hens has started to look increasingly like a drake. Her head is turning green. She now has a distinct white collar/stripe around her neck. She has the start of a curly tail feather and more of her other feathers are turning into the distinctive grey feathering that Rouen drakes have. It is the weirdest thing. She's 8 and hatched out four ducklings 6 years ago. I read somewhere that ducks can indeed change sex though it is very rare. At the very least, she is definitely changing her feathering to look more like a drake. Just curious is anyone else has seen this?