Last week, a day after the morning low temperature plunged to 9 degrees, the sky cleared and the thermometer rebounded to 45 degrees. That balmy afternoon bluebirds, chickadees, titmice, and Carolina wrens sang with springlike enthusiasm. It reminded me to get my nest boxes ready because all four species use boxes within 100 yards of my house.
Though only about 85 of 700 species of North American birds nest in cavities, many of those that do are welcome in backyards. Only cavity-nesters have the strong feet and fearless disposition required to explore deep, dark nooks and crannies. They earn their keep by consuming vast numbers of insects pests.
Because natural cavities are a limited resource, the best way to attract cavity nesters is to place nest boxes in suitable habitat. For example, pastures, hayfields, cemeteries, and golf courses are ideal for eastern bluebirds. Forest edges attract chickadees and tufted titmice, and Carolina wrens often stay close to homes and sheds.
A basic nest box for cavity-nesting songbirds measures 4 or 5 inches square (inside dimensions) and 10 to 12 inches high. The entrance hole should measure precisely an inch-and-a-half in diameter and be placed about an inch from the top. This hole size prevents bigger-bodied starlings from using the boxes. The front or side should flip open for easy cleaning.
Hang nest boxes 4 to 5 feet above the ground on a post protected from below by a predator baffle. The baffle is essential because unprotected nest boxes eventually become raccoon and rat snake feeders.
Here are a few more tips to keep in mind:
* To build your own nest boxes, use three-quarters to one inch thick stock. It insulates nests from spring chills and summer heat. Any untreated lumber will do, but three-quarter inch exterior plywood is relatively inexpensive and weathers to a nice rustic look.
* Assemble with rust-proof screws to extend the life of the box.
* It's not necessary to paint or stain nest boxes, but use light colored earth tones if you do. Light colors absorb less heat and are less conspicuous to vandals. Put a shingle or several coats of water sealer on the roof; it receives the greatest exposure and weathers faster than the sides. Do not paint the inside of the box.