Last weekend I built 4 nestboxes for my mandarins, woods, and hooded mergansers. They are 12" deep x 12" wide x 24" tall with a 4 inch circular opening. They are in a predator proof enclosure so I didn't think the oval opening was necessary. I used 3/4" plywood because the 12" wide pine or cedar solid boards at Lowes were so expensive. Because I used Plywood I painted the boxes with a white exterior grade latex paint. Will the paint cause any issues with the birds using the boxes? Should I paint a second coat of a more earthtone color? I am not sure wether or not ducks can even see in color so any help is appreciated. Also, I have two pairs of mandarins, one pair of woods, and one pair of hoodeds. Should I add another nestbox or two or should the 4 be adequate? I do probaly have enough wood for another box, but I was worn out after finishing the first 4 and got lazy.