how big does a birdhouse need to be for a bluebird
Boxes can be painted or stained with a light color on the outside and left natural on the inside. Birdhouses for Eastern Bluebirds should be approximately 4 x 4 inches to 5 x 5 inches with entry holes that are either 1 inch round holes, 1 3/8 x 2 vertical oval holes or 1 1/8 inch horizontal slot entrances.