First of all let me say that there is amazing variety of birds on our planet. We will only talk about some. The common ones, the ones in your city park, the ones in your back yard, the ones that you see every day on your way to school or work.

Bird houses provide nesting places to replace those lost to development. Recent studies indicate that the population of certain bird species, like Bluebirds and Tree Swallows, have actually increased due to the popular use of man made bird houses, as well as volunteer programs that track their breeding habits.

People of all ages enjoy watching birds, and for many of us it has become a passionate hobby. According to the US Fish and wildlife service, over 53 million Americans are enthusiastic bird watchers and over 59 million Americans enjoy feeding birds. That number is increasing all the time. It’s second only to gardening as the most popular hobby.

The beauty of bird watching lies in the fact that you can do it wherever you may be, whether you're in a city or town, out in the country, in an apartment building, or right in your own backyard!
Watching birds go about their everyday lives is often taken for granted, but it shouldn’t be. Forests and scarce breeding grounds are being swept away by new development and urban sprawl, severely threatening the natural habitat of birds and their ability to breed.
Although only a tiny percentage of known birds use bird houses, we provide them for good reason. Studies indicate that up to 80% of birds bred in bird houses will successfully raise at least one offspring, as opposed to open nests that have only a 20% to 40% survival rate.

During mating season, good shelter is becoming harder for the birds to find. The once inviting nooks and crannies of old trees are becoming extinct. Forests are being cleared of old trees because they don’t look good, or they're being harvested early for monetary profit.
There is strong evidence from wildlife biologists and ornithologists that natural cavities for nesting birds are becoming increasingly hard to find.
To meet the rising need, bird house placement programs have been initiated to fill the void and track the breeding habits of birds.

Here are a few tips for selecting appropriate bird houses for your area and the bird species that reside there:     
In general, most types of lawns and gardens will support different bird species, for example, a pair of chickadees, a pair of flickers, and a pair of robins.       
Each bird species will attempt to keep others of its own kind out of its territory, but will not usually be bothered by a different species.     
You should place several different sizes and types of bird houses around your property in order to attract a variety of nesting birds.
Providing food and shelter for your feathered friends will make their lives easier while enriching yours. Buy or build some bird houses and make your lawn and garden come alive!

Specs for Building Birdhouses.

Various species of birds prefer birdhouses of certain sizes. Of course, you will want to make the entrance hole large enough for the type of bird you wish to nest in it. The hole needs to be ONLY that size since larger holes invite predators, to invade the box, either killing the chicks or taking over the box and evicting the previous residents.
Here's a handy table to use when building birdhouses. Double check the bird house plans you are using to make sure all measurements are in order. Then settle back and enjoy bird watching in your backyard.