I should've checked out the Holderread book again from the library before buying the mixed ducklings. Well, I got a mixed flock of ducks from McMurray hatchery, where two didn't survive. So I bought 2 Cayugas. I have 2 female Rouens, 3 Rouens or Mallards, 2 Pekins, and 1 Cayuga (the other didn't make it). BTW, how do you tell a production Rouen from a Mallard? So, I thought I had all females. So, I bought 5 youngsters from someone who accidentally had 44 ducklings hatch. More on that later. Then, I discovered that one Rouen had drake feathers. And then the Holderread book stated that green bills were a sign of being male. So, I have 2 male Rouens/Mallards. Then, I started noticing that the Cayuga's quack is soft and more of a rasp. Another male? Then, I read about the sex-link colors. Oh no. The woman who I bought the ducklings from had one Khaki Campbell male which bred with a blue Swedish, Cayugas, Rouens, and Khaki Campbells. My little ducklings are the following colors: 1 black 1 blue 3 brown/tan/chocolate I'm now assuming because of the sex-link colors I have at least two drakes. I can't figure out what the patches of light tan under their throats indicate. It's like they're all marked like blue Swedish ducks but are brown. But one is like a Rouen. Females?