We had Muscovies for almost 40 years.
You need corn. Yes, they eat tons of insects, but in winter, be ready with the corn.
They fend for themselves. They went in the big barn where the cows were.
Hens were always laying and hatching in the hay bales at drop of a hat.
They average about 12+ hatching on a nest of almost 20 eggs- Temperature dependent and how often she leaves to drink water or get corn...
They could have a better success rate if you confined the hen to a big empty water tank and made a sturdy lid for her so she could mother without having to worry about predators. We had a pond about 1000 Feet away but they mostly stuck to the 2 Acres around the barnyard. (50-75 ducks sometimes on less than 2 Acres of ranging through cow pies in summer, eating fly larvae. That was the purpose of having barnyard ducks).