This is an annual reposting:
Just a couple of weeks left to get your new Wood Duck houses up, and, if you want to place your boxes in water, it's easier to do if you can walk on the ice and punch a hole to hammer a post into the shallows. That is, if you have any sturdy ice on your pond or marsh.
The males arrive to their breeding grounds in March, and hunt for nesting boxes and holes and crevices in trees before the gals arrive later in April.
If you have a stream or fresh water pond or marsh nearby, they will welcome your effort. Remember, there is no limit to the number of boxes you can place in or near a marsh - these birds are not territorial. I try to add one each year.
I place them on dead trees in the shallows of the beaver marsh, and nail a 3' aluminum flashing on the tree to deter coons and Blacksnakes. Some I put on a post in about 3-6' of water with a strong cement base. I always add a few inches of wood shavings on the bottom.
You can also put them in trees near ponds and marshes,
Our piece on Wood Duck here. I won't shoot a Wood Duck unless by mistake. They are highly edible, but too small. My joy is just to see them around, and my worry is just how many Snapping Turtles and egrets eat the young ones.
The best wood duck houses: http://www.bestnest.com/bestnest/duck_houses.asp (fixed). I had planned to build a few more this winter, but I never got to it.
Here's the Ducks Unlimited site on building and situating Wood Duck houses.