Build a box that will stay dry and warm. Place the roof of a birdhouse at a slight angle and extend it over the sides and front of the box. In this way, the roof will shed rain or snow and protect the entrance hole and sides from dripping water. Drill four, 1ǚ_inch holes in the floor to provide drainage if water seeps in. The sides of a nest box should extend down beyond the floor so water won't leak in.
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.