I have a single pair of ducks - Rouens - that I purchased last year. The hen laid about 3 dozen eggs this spring before being moved to the pond. Yesterday we hatch 8 of her babies, and... well... 5 of them are what I expected. Dark colored typical mallard colored ducklings. The other 3 are light in color and almost look like a chipmunk. Wasn't expecting that at all. Is this sexable breed based on color, or, are they a different color altogether?