Got Cavities?

There are many ways of attracting songbirds into one’s backyard.

An easy method is, of course, to put up bird feeders and watch the feeding frenzy that occurs.  Bird feeders are important because they help birds get the nutrients they need to survive, especially during migrations.  If you want to encourage birds to stay in your backyard, though, you might consider putting up birdhouses, or nest boxes.

Bluebird hatchlings inside a nestbox (photo: JoHanna Burton)

Birds that nest in boxes or other such hollows are called cavity nesters, meaning they nest in tree hollows or other such spaces that have already been created.  There are quite a few cavity nesting species in Missouri; our state bird, the Eastern Bluebird, is among them.

Now, you could put up any old birdhouse and see what decides to nest there, but some species are pickier than others. The Eastern Bluebird, for example, much prefers something akin to a box on a post than a box hanging from a tree. Carolina and House Wrens will nest in just about anything.

Another determining factor for a nesting pair of songbirds is location, location, location.  Eastern Bluebirds can be especially picky about this.  They prefer edge-like habitats – grassy areas with a few trees.  Golf courses seem to be great places to attract nesting bluebirds.

The size of the box will also determine what type of bird you attract.  Possibly the most important aspect of this is the size of the opening to the box.  It must be large enough to admit the bird, but small enough to deter larger competitors, nest parasites (Brown-headed Cowbirds), or would-be predators.

If you want to attract smaller birds, like wrens and chickadees, the opening should be approximately one and one quarter inches in diameter.  For slightly larger songbirds, such as bluebirds, the opening should measure about an inch and a half across.

Woodpeckers are also cavity nesters (photo: Gay Schroer)

Certain birds of prey are also cavity nesters, such as the Eastern Screech Owl and American Kestrel.  To encourage these birds to nest near your yard, you’ll need a larger nest box, with an opening of three inches in diameter.

If attracting a certain species of bird to nest in your yard is your goal, it is important to do your research first, remembering that the type and size of the box as well as its location can be important to nesting pairs.

Not handy enough to build your own nestbox?  To begin your career as a “birdy landlord” stop by the World Bird Sanctuary’s Wildlife Hospital where we have nestboxes available for purchase at a minimal cost. 

Submitted by JoHanna Burton, World Bird Sanctuary Naturalist