We have 1 Cayuga drake and 2 females, 1 welsh harlequin drake and 2 females that have been raised together since hatching, just over a year ago. I understand that a 3 to 1 ratio of hens to drakes is preferred but we lost 2 hens to predators last summer.
In this case, more females wouldn't offer her much peace since she is the preference. More hens that are just ignored won't change anything.
Mainly the WH drake pursues her aggressively, and especially when I let them out of the coop in the morning. They free range and head over to a small pond/large puddle on a vacant lot next to us. They forage and swim freely (with permission from the owner) and just consider this an extension of our land. While they are out and about, the drake doesn't harass her but when they return to the coop for a midday snack of feed, he'll be at her again. She dodges, runs and avoids him but when he does mount her, it attracts the attention of my Cayuga drake and he'll peck her head while the other drake is atop her. Sometimes he will also try to mount after the other drake but at least he is less persistent than the WH drake.
She was often the one lagging behind the flock and earned the name Lost, as she would quack to find the rest of the them after doddling too long. But now it seems she's deliberating leaving the group and keeping a greater distance from the others- only sometimes though, mostly they stick together and like I mention, when they are in their swimming hole or the field, I don't observe this behaviour.
She seems healthy and no loss of feathers. Do I need to be concerned for her? I also have no idea what goes on at night when they're confined to smaller quarters and she'd have less ability to evade him. No signs of excessive feathers in the morning (good sign). Although, late winter this was the case- many feathers, mostly from the WH hens and those girls were looking a little battered. In that case, I separated the hens and drakes but their hormones died down quickly and I didn't have to segregate them for more than a week. The process of catching the drakes stressed them al so I didn't want to do it for longer than necessary.
Thanks in advance to the more experienced duck keepers than me, that may have some advice.