Wild Bird Nesting Box Measurement Requirements

Erecting nest boxes is a great way to attract birds to your garden. These boxes offer wild birds the opportunity to not only shelter, but to incubate their eggs and raise their chicks as well. Avoid painted or stained wood however, as the fumes from painted nest boxes are toxic to birds and the wood loses its insulating properties when its pores are filled with paint. Redwood and cedar are good woods to choose for your nest box construction, but 5/8-inch thick plywood is also acceptable.

  1. Specific Dimensions

    • Many wild bird species accept a variety of nests, but you have more success in attracting specific bird types if you put up nesting boxes of the correct dimensions. Larger species, such as kestrels and screech owls, need a floor space of at least 8 square inches, while smaller types of birds, such as the flycatcher, require a floor space of only 6 square inches. Woodpecker species, such as the red-bellied and red-headed woodpecker, are also comfortable with a floor space of 6 square inches. A height of 12 to 15 inches is suitable for red-bellied, red-headed woodpeckers, kestrels and screech owls, while an 8 to 12-inch-high box suits smaller species such as the flycatcher.

    Preferred Height

    • Always position nesting boxes for screech owls and kestrels between 10 and 30 feet above the ground. Different species of woodpeckers also prefer to nest high; boxes for the red-bellied and red-headed woodpecker should be in the region of 20 feet from the ground. Position a nest box for the pileated woodpecker a little higher, at 30 feet above ground level. Purple martins prefer to nest between 10 and 15 feet from the ground, while you can place the best box for flycatchers slightly closer to the ground, at a height of between 5 to 15 feet.

    Entrance Size

    • The size of the entrance hole is vitally important. An entrance hole that is too small is of no value to the species for which you built the nesting box, while an entrance hole that is too large allows predators and aggressive bird species access to the box. Entrance holes with a diameter of between 2 and 2 1/2 inches are suitable for red-bellied and red-headed woodpeckers, while kestrels and screech owls require an entrance hole of at least 3 inches. An additional piece of wood around the entrance hole adds depth to the area around the entrance, and prevents some predators from reaching into the box. Perches at the entrance hole are not necessary and benefit predators more than the resident birds.

    Important Considerations

    • Provide ventilation for the nesting birds by drilling ½-inch holes along the top section of both sides of your box. Another option is to leave a gap between the sides of the box and the roof. This gap must not be too large, or it will let unnecessary amounts of cold air. A ¼-inch gap is quite sufficient.