Duck ID and how many drakes?

My wife got these from tractor supply. I swear when they were little they had a second black line under the eye which made me think rouen. I also saw a green sheen on all of their heads weeks ago. But now I really only see it on 1. But looking at the bills it looks like 2 and 2. So I'm not sure if they are mallards or rouen and if 1 to 4 drakes. Lol. Any ideas from people who know more than me?

I think you have 4 Mallard hens

Welcome to permies, James!

Yes, that's the age old question! I don't know my breeds well enough to suggest an answer to that, but they look old enough that they should either "quack like a duck" or not! Younger males will make a sort of wolf-whistle noise, particularly if concerned about something, but they loose that as they mature and make a fairly quiet noise from then on. Females go "quack, quack, quack" which is why I refer to all the mallard-derived ducks as "Noisy Ducks" - I have the mostly Khaki Campbell version myself. A few of them are just starting to quack and the oldest are just 7 weeks and the youngest a couple of weeks younger.

I also have Muscovy, which are a meat bird, and really aren't a duck at all, although many refer to them as such, and they are much quieter and calmer.

The drakes in both breeds will have a solid green head  with a white ring around the neck.

The Rouen grows quite a bit larger (6-8 lbs) and those hens have 2 black stripes on the head.