If the entry hole is too large it may allow a competing bird to take over the box. Starlings and House sparrows are very aggressive and will kill the babies and adults of many birds, including bluebirds. Pick the plan for the species that you hope to attract and follow the specifications. To see a chart listing the dimensions of many nesting boxes click here . The Plans that are listed to your left include a drawing and will have detailed information on building the house.
Wood makes a great bird house.
It's durable, breathes, and insulates. Three quarter inch thick bald cypress and red cedar are best. Pine and Plywood will do but they will not be as durable. Exterior colors that birds seem to prefer are tan, gray and dull green. Dull, light colors reflect heat and are less obvious to predators.