Northern Prairie Wildlife Research Center
Water requirements for bluebirds are assumed to be met when the birds nest in areas with suitable nesting and wintering habitat. The bluebird's foraging behavior and the types of food eaten provide it with an adequate amount of water.
In order for successful bluebird reproduction and survival to occur, all required habitat components must be available in relative proximity to one another. Since bluebirds are migratory and highly mobile during winter, the most critical aspect of habitat interspersion, or the mix of different habitat types, is the proximity of suitable foraging habitat to nesting habitat in the spring. The highest-quality nesting habitat is of little use if the nearest open foraging habitat is not within close proximity. Likewise, the best foraging habitat will not support nesting pairs if there are no available nest cavities. Ideal interspersion of the bluebird's required habitat components consists of a complex of open grassy fields, either mown or of low growth, widely scattered trees, berry-producing shrubs and vines, snags, and perches in the form of trees, shrubs, utility wires, telephone poles, or fence posts.
Minimum habitat requirements become an issue only when two or more nesting pairs desire to nest within one general area. Because bluebirds are territorial, nesting pairs typically will nest in cavities that are separated by at least 100 yards. Thus, nest boxes should be spaced at least 100 yards apart if more than one box is placed in an area. In general, an area the size of a football field is needed between two boxes for the boxes to be most attractive to bluebirds. Lands outside the immediate planning area should be considered when making the determination of minimum habitat area for bluebird reproduction.