Build a house for a specific bird. Build a birdhouse for a cavity_nesting bird that occurs in your region and lives in the habitat in which you plan to put in a birdhouse. (See Birdhouse Dimension Table to select a species.) Build the right size house and hole dimensions. Different species of birds require different sized houses and entrance holes. Inside dimensions must be large enough to accommodate the incubating biard and a brood of growing young. Entrance hole size is especially important. If the hole is too small, the bird you built the box for won't be able to get inside. If the hole is too big, predatory birds and mammals will be able to get inside and reach the nest, and cavity_nesting birds may not use the house.
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.