Once you start feeding backyard birds, the next natural step is to put up a few birdhouses. Whether you buy birdhouses or build your own, you're sure to feel proud and excited when a pair of birds set up housekeeping in your yard.
Birdhouses attract a wide variety of birds, but not all birds. Birds that use birdhouses are cavity nesters, such as bluebirds and woodpeckers. Birds like tanagers, which plaster their nest to tree limbs, or catbirds, which hide their nest in a thicket, won't be interested in your nest boxes. Neither will ground-nesting birds like thrushes, native sparrows and towhees.
That still leaves plenty of possible birdhouse tenants, from wrens to woodpeckers to owls. These are birds that chisel their own home in a dead tree limb, wooden fence post, or utility pole, or use a hole created by natural causes. Still others are birds that adopt an old woodpecker home. Robins, phoebes, and barn swallows won't nest in a closed box, but they will build a nest on a roofed shelf.
Most cavity-nesting birds have trouble finding nesting sites these days, because wooden fence posts are outdated, replaced by metal posts. Also, farmers tend to remove hedgerows between fields, meaning less dead trees. Putting up birdhouses in your backyard sounds like a small gesture, but it's a matter of survival for cavity-nesting birds in your neighborhood.
The best time to put up birdhouses is in late winter. Most cavity nesters are early birds when it comes to nesting. They begin house hunting as early as January or February, and most woodpeckers, chickadees, titmice and bluebirds are sitting on their first batch of eggs by March or April.
Male house wrens, who arrive before the females in spring migration, try to make up for lost time by constructing nests that only need the stamp of approval from the female when she finally show up.
Don't fret if you've missed the time of first nesting. Mount your bird boxes whenever you make them or buy them. Birds continue nesting through June, either raising second broods or replacing a failed first nesting, so a new house may still get tenants even if you put it up in May. Get a birdhouse for Christmas? Put it on a tree instead of on a shelf in your closet.
Select a birdhouse to fit the bird's needs. Plain, unpainted wood is very appealing to birds, because it looks like the real thing: a hole in a tree. But fancy houses are fine, too, though they take a little longer to attract tenants. Nesting holes are usually in such high demand that any kind of structure will soon have a taker.
Two or three basic sizes of birdhouse will suit the needs of most backyard birds. The diameter of the entrance hole, not the size of the box, is the main factor that determines which birds will use the birdhouse. A box with a large hole will work for a variety of birds; houses with small holes will allow only small birds access. A small entrance hole will keep out certain birds that you may not want to encourage. House sparrows, for example, will nest in a box with a 1 1/2" entrance hole, but a 1 1/4" hole will keep them out. Starlings need an opening at least 2" across.
Whether you go plain or fancy, make sure the birdhouse is well constructed. Joints should fit snugly, with no gaps for rain or wind to enter. A hinged side makes clean-up a snap. The roof should overhang the entrance hole, so that rain doesn't drip in on the vulnerable babies. Flimsy houses made of thin, cheap materials may crack or spill out under outdoor conditions, which could be fatal to any birds inside.
Mount your houses on a pole or tree by driving stout nails into the back board. Mount houses with the entrance hole facing east, so that cold north winds and driving rain, which usually come from the west, don't blow directly into the box. An east-facing entrance collects the warm morning sun, too, but not the strong glare of southern exposure. Make sure the house is secure and cannot be tipped by strong wind or climbing cats. If you mount it on a post, a predator guard is a good investment. Purchase a metal or plastic baffle that will fit over the pole below the house like an inverted funnel, blocking access from any wild things with designs on the inhabitants.
You can keep your birdhouses up all year long, to accommodate any wild friends seeking shelter, whether they're roosting birds, hibernating bats, shelter-seeking mice, or wooly bear caterpillars. If your house is a work of art, you may want to take it down in early fall and store it out of the weather to prevent damage. It's not necessary to clean houses at the end of the season - cavity-nesting birds have gotten along just fine in the wild world.