Sundown........Wood ducks will breed the first year, Mandarins are usually the second year so yours should be good for you this year.
I have my boxes up now, depending on the weather, the Wood ducks will be around April, Mandarins shortly after. You want the boxes up early so they can have the time to check them out........it is always best to put up more boxes then breeding pairs that you have. Too little nesting choices and you will get other hens dumping her eggs in a nest that is already in use.