Some background info for those who are interested.
A birdhouse has two types of origin: European and American. Each has its own unique history.
European birdhouse (clay style)
The European clay birdhouse originated from Belgium and Holland and goes back to the 15th or 16th century. Its original use was not to protect the animal but as a trap for eggs and chicks as food. In the beginning, wood, basket, or pottery was commonly used but since organic materials do not last, the clay style eventually prevailed. Depending on the era, the clay birdhouse was used as ornaments or talismans in addition to protecting wild birds.
American birdhouse
The American birdhouse finds its roots from the Native Indians who taught the English and German immigrants moving to the east coast of the United States in the 18th century. It was a simple structure made from the bark of birch trees with a platform as a feeder. Even to this day, American Indians are making birdhouses in the same way. The birdhouse sheltered birds from storms and natural disasters. It also played an important role in breeding as well as propagation of species. Nowadays, birdhouses in the shape of tiny castles, churches and Victorian cottages are in the market as folk art.
There are several aspects of a bird house that determine which type of bird it will appeal to. Specific bird species choose whether to build nests in bird houses based on several factors. One of the most important aspects of a bird house is the diameter of the opening. Larger birds require a larger opening for access, but most small birds prefer a smaller opening in order to prevent other birds from raiding the nest.
Another important aspect is the size of the house itself. Different sizes suit different species of birds; for example, very small boxes attract wrens and treecreepers and very large ones may attract ducks and owls. The type of material used is also of importance. Woodcrete is warmer than wooden nests, a characteristic that suits some species better than others. Finally, the placement of the birdhouse is also important. Some birds prefer their nest box to be at a certain altitude at the tree, some birds prefer them to be very low or even at ground level. Also the orientation to the sun is of importance (south facing ones -in northern hemispheres- tend to be warmer than south-facing ones).