The older duck has been with the drakes for over a year, since hatching. She actually misses her boys and doesn't seem to suffer from over mating! However, the set up we have now, the girls are in the duck pen (with the pond) during the day while the boys are just loose in the backyard and we close the girls in the coop at night and the boys get the pen and pond all night, but are vulnerable to predators. They are pretty fierce, though. They chase our 75# dog around the yard! LOL We just don't have anywhere else to keep them because we have a broody chicken sitting on 8 eggs in our spare coop! It's a good set up because the ducks are all side by side and the boys aren't showing aggression to the babies any more, but the 3 adults REALLY miss each other! And our female's eggs aren't fertile any more and we have another chicken gone broody and no fertile eggs to put under her!
Anyways, it'll be better once we can put the boys and girls together again, but I don't want the babies to be hurt by the drakes. It's crazy because the babies are only 9 weeks and yet the size of the adults!