muscovy ducks dont use the house to sleep in anymore?

[animals1981]

When my ducks were really young they would cuddle up in their dog house at night but now even on nights when it gets -20 neither ducks use their house! the big drake lust sits on top of it and the little female sits below

Is this what happens they they grow up they don't go in a house to Sleep?

 

[animals1981]

Also when i let my ducks out is there anyway to make sure they come back to the coop at night so they dont get eaten by predators?