Here is a simple ideas to help you build a great duck house of their own and to provide them with the peaceful environment they need to nest and reproduce.
Build a Floating Platform
Protecting the ducks from predators is the main goal of building them a nesting house. Raccoons love to eat the eggs and they will find ways to get them. If you have a pond, a floating house is a great option to provide them a safe place to nest.
Use a sheet of thick Styrofoam and cut it in a half. This will be great to keep the nesting house floating. Join the two pieces of Styrofoam together with 2 pieces of 2x4 or simple boards, leaving a space in between them. Once you have a solid foundation for the floating house, build a platform over the Styrofoam with wood boards. Make sure not to use pressure treated wood, which is bad for the environment.
It will be much better not to have the duck house sitting right on top of the platform. The Mallard house needs to be elevated a little, this is good for a floating house as well as a house on solid ground. This is necessary to protect the nest from getting wet from the rain and the possible waves of water coming on the platform on windy days. For houses on the ground, the possible variations of water elevation in the pound may flood the duck house after a big rain storm so you need to keep that in mind.
I strongly recommend to use plans to build a mallard bird house to help you doing this project. This is my favorite source for woodworking plans, and it includes over 16,000 different ones.
How to Build a Mallard Nesting House
You can do that by installing two pieces of wood across the platform. Them build a roof by using two pieces of plywood and installing them on the top of the nest forming a triangle shape all the way to the platform.
So weather you choose to build a nesting house or a floating one,
I just found great Delta WaterFowl's Videos about how to build nesting tubes for ducks. Check em out!