My ducks once had the same problem the only option is to some how block the swinhoe or take it away I caged of my female and let her have a peck around every now and then its the only solution
I agree, they shouldnt be penned together anyway. The mess ducks make is very bacterial rich and can kill any pheasant.
For egg eaters though, you have to snip off the top 1/3 of their upper beak, basically get the "egg breaking" point off it. This will hold you over for about 4-5 months after that, they are usually broke from eating them, but if you notice it happeneing again, you have to clip it again.
Dont go real deep, but yes you want it to just barely bleed a little. Look at the beak very close, you can see when the inner core starts, it will be a different color and right at that spot is where you want to cut.
I hve used this method for many decadeds to stop egg eaters in everything from bantams to wild turkeys, pheasants included, it works very well. Just watch her and see if she goes back to it, 9 out of 10 will not though.