The dimensions of your birdhouse should cater to the specific species you're aiming to attract, as different birds require different sized entrance holes and interior spaces. For example, a birdhouse for chickadees should have an entrance hole 1 1/8 inches in diameter, while a bluebird house should have a hole that is 1 1/2 inches. Research the preferred dimensions for your target species to ensure the birdhouse is suitable and safe for them.