How important are drain holes and ventilation openings in bluebird boxes?
Some ventilation is important as nest boxes should be placed in open areas and away from trees that would normally >provide shade, except where such shade is provided by a single tree. Ventilation holes or slots should be located on both sides of the box just below the roof Boxes with large overhangs, such as the Peterson Bluebird Box, do provide adequate protection from rain, and as such, do not require drain holes. Other nest boxes lacking the extended overhang should have the four comers of the floor cut off. This produces triangular drains at each of them. This allows drainage for any water that accumulates inside the box, as well as moisture from condensation. The floor of the nest box should also be recessed 1/4 inch above the four sides to prevent the floor from absorbing water.
