Females are drab versions of the males . Populations of these birds have grown rapidly over the past few years, mostly in response to people constructing and placing nest boxes. Bluebird Trails where boxes are placed along paths through good bluebird habitat have been established in many states. This partially compensates for the loss of preferred nesting sites such as wooden fence posts and cavity trees. Before bluebird boxes were erected in great numbers, starlings and house sparrows reduced the bluebird population by competing for and winning available nesting sites.
Bluebirds usually nest along woodland edges of open fields or other open areas.
They are often seen along farm fields, golf courses, and pastures. Nest boxes placed along the edges of these areas are preferred nesting sites. A good supply of insects and berries are essential to this songbirds. It does not usually feed at bird feeders. Nest boxes should be placed 3 to 5 feet above ground and at least 25 feet from the nearest tree.