Rouen Ducks: Male or Female?

Our sweet little ducklings are all grown up.  Except for their feathers.

When we got these guys, we hoped for 2 things:

1)  that they would be Rouens and not Mallards
and
2)  that there would be one male and one female.

Over the last few months, after much research, we have found that we do indeed have Rouens, not Mallards, which we are incredibly thankful for!!

Then one of the ducks started to develop his white collar and green head feathers, indicating that he is indeed a he!  So, again, we are thankful.

But just today, I noticed a white spot on the other one.  The spot is on the front of the neck in about the same place as the other one's white collar.  Sheesh.  So now, I'm not sure if we have two males or a male and a female.

When the male started developing his white collar, it came in very quickly, so I'm hoping to know for sure within the next week or two with this one if it's going to get that same collar.

Fingers crossed that we have a male and a female so we can breed them and have some sweet little duckie babies in the spring!!

**UPDATE:  They both ended up being males.**