Cavity Nesting Species

Picture of a squirrel.Cavity nesting birds and mammals such as woodpeckers, chickadees, titmice, great-crested flycatchers, bluebirds, and squirrels nest in tree cavities which they excavate themselves or which were excavated by another cavity nesting species. The limiting factor for many of these species is the number of cavities which are suitable for nesting.

In order to make more cavities available to these animals, landowners can either increase the number of natural cavities or provide artificial nest structures.

Natural Cavities

While managing a woodlot, landowners should consider the number of cavities available for nesting by birds and mammals. Live trees with existing cavities should be given preference because they last longer than dead trees with cavities. The ideal density of standing live or dead cavity trees is an average of 10-20 small (<12” diameter) and 2-5 large (>12” diameter) cavity trees per acre. Be sure to choose at least one tree per acre which is greater than 12 inches in diameter because pileated and red-bellied woodpeckers will not use smaller trees.

If your woodlot does not contain a minimum number of cavity trees, you can create some by herbiciding an average of five trees per acre each year. This operation should be timed with any planned thinnings in the woodlot. By selecting trees such as red maple, sweetgum or poorly formed trees, you can improve timber quality while creating wildlife habitat on your forest land. Also, healthy mast trees (i.e. oaks and hickories) should not be herbicided as they produce nuts which are beneficial to many species of forest wildlife. If your woodlot is being impacted by gypsy moth or other forest insects or diseases which will ultimately cause trees to die, then herbicide use is not necessary.

Artificial Nesting Structures

Bluebirds, wood ducks, barred owls, and squirrels are just a few of the species which can benefit from the establishment of artificial nest structures. Historically, they nested in natural tree cavities, but fewer natural cavities and/or competition with other users of natural cavities may have depressed their populations locally.

Nest boxes are readily accepted by some species and can be used where natural cavities are limited or not practical. The Virginia Department of Game and Inland Fisheries' publication titled “Wildlife Plantings, Boxes and Platforms” will provide you with the specifications for constructing the structure needed.

Some general guidelines for several species are:

bluebird - minimum two boxes, 10-15 feet apart, at least 1 acre open ground in front of box; no perches.

wood duck - one box per acre of impoundment; one box per 50-75 yds of stream/river; always include a predator guard.

Maintenance of nest structures is minimal. The boxes should be checked annually to make sure they are weather proofed and have not accumulated an excessive amount of nesting material.