Bird houses are an excellent way to attract more avian visitors to your home while accentuating your backyard décor. They also provide those bird species that brave the winter with warmth and shelter at a time of year when both are difficult to come by.
Decorative bird houses are available in a wide range of styles, some of which are suited to particular species. For example, if you live in an area rich with orioles, purple martins or cardinals, you can tailor your wild bird houses to ensure the dimensions and features are suitable for the species in question.
The most common style among wooden bird houses is the closed bird house. These houses feature wall closures on all sides, a roof and an entrance designed to admit only one bird at a time. In multi-compartment closed bird houses, the entrance is typically placed atop the middle compartment to inhibit predators from gaining entry and to protect the birds from the elements. Most small bird houses are closed, since it's primarily smaller birds that benefit most from the protection they offer.
Open and platform designs are particularly attractive to bird species that are classified as platform nesters. These include herons, hawks, owls and other large bird species like pigeons and gulls. The defining feature of these bird houses is that all four sides are open, with a suspended roof offering the birds protection from the elements.
Birdwatching experts stress that it's best to build your bird house for a specific species; this will give you the best chance of attracting birds to your yard.
When choosing or building bird houses, opt for designs that offer adequate ventilation. Without it, the bird house will become a stifling sauna in warm weather, posing a potentially life-threatening danger to any birds that enter it.
You also need to pay close attention to the bird house's drainage system. Most often, a slanted roof and a small hole in the floor of the house will provide adequate drainage of rainwater, but more complex designs will need more complex draining systems. The built-up pools of standing water that result from bird houses with inadequate drainage systems pose a serious danger, as these water pools are hotbeds for disease and parasites.
Finally, keep in mind that some bird species will not use closed bird houses. Swallows and mourning doves are two examples. If you want to entice these to visit and stay in your yard, choose an open or platform design instead.