Khaki duck egg laying question

This is my first time raising khaki ducks, I have 4 girls and was wondering about when they start laying eggs. They are now 5 months old and are let out every morning with the hens to roam the property every day and go back in with the hens on their own in the evening. I guess the question is do they go back to the hen house/pen to lay or will they just lay in random places?? Should I be looking around for their eggs?