What kind of nest do bluebirds prefer?

Bluebirds typically nest in cavities, such as holes in trees or walls. They prefer large cavities that are at least 1.5 inches deep and have a diameter of around 4 inches. The cavity should also be located in a sheltered spot, such as under a branch or in a dense bush. Bluebirds will often use nesting boxes that are specifically designed for them, as long as they meet these requirements.