In addition to food and water, shelter or cover is a critical component to any animal's habitat. Many species of animals require cavities in which to raise their young: bluebirds, Carolina Chickadees, Tufted Titmice, woodpeckers, flycatchers, Screech Owls, American Kestrels, nuthatches, Purple Martins, wrens, and Wood Ducks. Others seek out cavities for shelter: grey squirrels, flying squirrels, mason bees, bats, rabbits, opossums, and skunks.

Before selecting a bird house, check the specifications for the species you hope to attract. Many houses are built similarly, but small differences in hanging height and hole size differ between species. Depending on the target species, there are certain requirements, as follow.

Bluebirds

Eastern Bluebird numbers have decreased by ninety percent in the eastern United States over the past sixty years. Many have attributed this to competition with nonnative species, the loss of trees with nesting cavities, and the prevalence of insecticides. Anyone can assist this species by avoiding the use of pesticides, leaving dead or dying trees which will provide nesting habitat, and adding nest boxes. Nest boxes should be hung by the end of February in open areas, facing south or southeast, located away from structures, mounted on posts with the addition of a predator baffle.