Minks are my main predator here on Vancouver Island.
There are no foxes or coyotes here although there are in the rest of Canada. I've also lost one bird to a hawk, another to a raccoon and one badly mauled by a feral cat.
I have mink and raccoon traps set at all times and my runs have wooden flooring and 3/4" hardware cloth. The most recent run has a 1/4" spacing between the floor boards and hardware cloth underneath.
The hens are allowed to free-range on days when I know I can be there at dusk to lock them in and the muscovies only get out when I can be there. Anyone who's had a mink attack will understand this. Also, when the muscovies are out, their shed is locked.
When the hens are out, the main door to the henhouse is wide open to facilitate escape.
That's just the way it is when there are so many predators.
I'll be giving up on the muscovies and am looking for some other waterfowl to replace them. They are simply no match for fast, furry things and locking them up 23 hours a day brings joy to none of us.