It’s time to hang spring nest boxes, and here’s how

Last week, a day after the morning low temperature plunged to nine degrees, the sky cleared and the thermometer rebounded to 45 degrees.

That balmy afternoon, bluebirds, chickadees, titmice and Carolina wrens sang with spring-like 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.Cavity lovers. 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 song birds measures four or five 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 four to five 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.

• Be sure the box can be opened from the front or side for easy cleaning and monitoring. A box that can’t be opened and cleaned is worthless after one nest.

• Extend the roof at least five inches over the front of the box to protect the hole from wind-blown rain and marauding paws. Drill four quarter-inch drain holes in the floor so the box drains well if it gets wet.

• Never put a perch on the outside of a box. Cavity-nesters have strong feet and easily cling to wooden surfaces. A perch invites house sparrows to use and defend the box.

• Finally, boxes should be in place by mid-March. Use plastic coated electrical wire to strap boxes to posts. Hang boxes so they will be shaded during hot summer afternoons, and orient the hole to the east to avoid prevailing winds and driving rain.Bigger nest boxes with larger entrance holes attract bigger birds such as kestrels, screech owls, and wood ducks. For detailed nest box plans for a variety of species, visit http://www.birds.cornell.edu/nestinginfo/nestboxref/construct.

If you lack tools and a workshop, purchase nest boxes at wild bird stores and nature centers. The Pennsylvania Game Commission (PGC) also sells a variety of surprisingly affordable next boxes; a set of two bluebird boxes, for example, costs just $30, delivered.

The PGC also sells nest boxes for kestrels, screech owls, wood ducks, mergansers, squirrels, and bats. To order, call 1-814-355-4434, or visit www.pgc.state.pa.us and click on “Howard Nursery” from the “General Store” drop down menu and then select “Wildlife Homes Order Form.”Cavity-nesters have already begun searching for and exploring cavities, but nest building usually doesn’t begin until late March or early April.Hanging nest boxes now makes them a part of the natural landscape so birds are more likely to use them.