Getting ducks to lay in coop? any tips?

[Luv Ducks]

Our days are getting shorter here in Ohio but two of my ducks are still laying. They have a large area that they live in and one of them will lay an egg just about anywhere. I wanted to get a trail cam to see which duck was doing it so that I could possibly confine her. I don't have an SD reader on any of my equipment and I am not sure if it is worth the cost to find out. My Mallard for sure lays inside one of the houses that I have for them. The other duck which is either a Khaki Campbell or a Muscovy just plops it down anywhere and will bury it in the mud if she can find some. The ground has been frozen so she hasn't been able to for the past few days. Mine don't lay until between 9-10 am.