While it is okay to paint the outside of a bird house, do not paint the interior surfaces or the inner rim of the entrance hole. Furthermore, use only environmentally safe paints, stains or varnishes on the outside and avoid any lead_based paints that can poison birds from fumes or ingestion. Choose a bird house design with the proper interior dimensions for the desired residents: Too small of a house may cause growing birds to smother, while too large of a house will not be attractive to nesting parents. Smaller birds could also become too chilled in a larger house if they are not huddled together when needed.
Nesting Ledges. American Robins, Say's Phoebes, and Barn and Cliff Swallows will not use nest boxes, but they will next on platforms that are open on three sides. Platform nest ledges should be 6ν inches wide, 6ν inches long, and at least 8 inches high. Nest ledges can be easily fastened under the eaves of houses, buildings, bridges or on trees. They may be placed near a window where the behavior of birds using them can be easily observed. Place the nest ledge 8–16 feet above the ground.