The Size of Holes for Birdhouses

Attract bluebirds to your property with good nesting boxes.

While birdhouses are often uniform in size and shape, the entrance hole has a great deal to do with what birds you get. Understanding the importance of the size of the hole is the first step to determining what kind of birdhouse you want.

Types

Bluebirds, Carolina wrens and swallows all prefer holes that are about 1 1/2 inches in diameter. Titmice, Berwick's wrens and downy woodpeckers all prefer holes that are about 1 1/4 inches in diameter. Different birds have their own hole requirements, from 1 1/8 inch for a chickadee to 2 inches for a red-headed woodpecker.

Exception

Purple martins nest in colonies, and not only do they prefer communal birdhouses, they also require a birdhouse entrance that is a crescent or a half-circle. This style of entrance prevents starlings from getting inside and it also protects nesting purple martins from screech owls.

Open Sides

Barn swallows and phoebes prefer to nest in open-sided nests, as this allows them a clear look around at their surroundings. Instead of a closed box with an entrance hole, provide these birds with a shelf to nest on.

References

• Baltimore Bird Club: Homes for Birds
• Bird Bath and Beyond: Birdhouse Hole Size Chart
• Purple Martin Conservation Association: Attracting and Managing Purple Martins