My ducks and hens roam together most of the time, but although I lock the hens in at night, the ducks are left out in the orchard. We don't however have the predators that you might have.
We have Australian brushtailed possums, Australian hawks, hedgehogs, rats and ferrets which could take a small bird, the ferret being the worst, but we seldom see those. Rats I put bait out for, Possums tend to prey on fledglings and eggs of small birds and some of our native ground birds, and hawks wont tackle a grown hen or rooster. Our birds are relatively safe during the day to be out.