Birds prefer houses that mimic the cavity size of natural nesting places. Most live in a house with one entrance and compartment. It's important that the entrance to the house only be large enough to allow entry to the appropriate bird.
The diameter of the entrance hole should be tailored to the type of bird attracted. The entrance should be set well above the middle of the compartment to protect eggs and babies from predators and inclement weather.
Chickadees need a 1 and 1/8-inch diameter entrance hole to their house. The chickadee birdhouse should be placed 6 to 15 feet off the ground.
Wrens, Woodpeckers, Nuthatches and Titmice
A little larger in their physical size, Titmice, Nuthatches, Downy Woodpeckers, and Bewick's Wrens use birdhouses with 1 and 1/4-inch openings. Nuthatch and Bewick Wren birdhouses should be hung at 6 to 10 feet, the Titmouse house 6 to 15 feet high and the Downy Woodpecker between 6 and 20 feet high.
Bluebirds, Swallows, and More Wrens and Woodpeckers
Bluebirds, Swallows, Hairy Woodpeckers, and Carolina Wrens require a birdhouse with a 1 and 1/2-inch entry. Bluebird and Carolina Wren houses should be hung 5 to 10 feet off the ground. Swallows prefer a height of 10 to 15 feet above ground and the Hairy Woodpecker needs a birdhouse placed 12 to 20 feet high.
Flickers and Flycatchers
Red-headed Woodpeckers and Crested Flycatchers nest in birdhouses with 2-inch entrance holes. Their houses can be placed up to 20 feet above ground. The Flicker will make a home in a birdhouse with a 2 and 1/2-inch entrance, placed similarly to the Red-headed Woodpecker.