Bluebirds nest in holes in trees, either in naturally-formed tree cavities or old woodpecker holes. They often select trees with a thick crown of large branches, such as elms and oaks. They are also known to use birdhouses, but it is important to choose a site with open areas so the bluebirds can roost in safety away from predators and raindrops.
Whenever a male and female bluebird pair are incubating their eggs, they will roost nearby. The male will protect the nest cavity while the female incubates the eggs. The male will also help feed her by carrying food to her while she sits in the nest. The female will not abandon the eggs, but she will only leave the nest to find food.
After the bluebird chicks hatch, they will roost on a branch or in the open air. Young birds do not have the ability to regulate their body temperature, so they rely on their parents for warmth while they are sleeping. They will not sleep on the ground, as they would be quick prey for hungry predators.
If you are interested in providing shelter for the bluebirds, you can construct a bluebird house or place mealworms in a feeder to attract them. Bluebirds also enjoy fresh, moving water, so if you have a bird bath, make sure it is not treated with chemicals. A heated birdbath is even better! The more shelter you provide for bluebirds, the better chance they will return in future seasons. In fact, many pairs that bred in one year will re-nest in the same location in the following year.