A well-constructed birdhouse (aka Birdhome) can provide a safe and welcoming home for many bird species. To ensure your birdhouse is both attractive and functional, consider these essential features:
Building Material
The choice of building material is crucial for a birdhouse. Opt for untreated, natural wood like cedar or pine, as these woods are durable, weather-resistant, and free from harmful chemicals. Avoid pressure-treated lumber, as it can release toxic fumes that may harm birds. Screws have extremely durable grip and have a hard time wiggling loose making them an excellent choice for fasteners.
Ventilation
Proper ventilation is essential to maintain a healthy environment within the birdhouse. Small ventilation holes drilled near the top of the side walls can allow for adequate airflow. This keeps fresh oxygen moving through the nest and help keep it cool during warmer months. These holes should be small enough to deter predators but large enough to permit air circulation. 
Drainage
To prevent mold and mildew, incorporate drainage holes in the bottom of the birdhouse. These holes should be small, and in all four corners of the box this will allow rainwater to drain out easily and prevent mold and mildew. Grooves cut on the bottom of the roof help channel rainwater away from the box and keep everybody dry. 
Predator Protection
Protecting birds from predators is a top priority. To deter cats, raccoons, and other predators, position the birdhouse on a pole or mount it high on a wall. The opening into the birdhouse should be small enough to prevent large predators from getting in but big enough to allow the birds to get in and out with ease. Suprisingly NO PERCHES. Birds do not need perches and they serve as another thing for a predator to use as a hold in order to gain access to the nest.
Box Size
The size of the birdhouse should be appropriate for the intended bird species. For example an owl will need a bigger box than a bluebird. Research the specific requirements of the birds you wish to attract to determine the ideal dimensions. There is no way to guarantee that only specific birds will show up to specific dimensions but narrowing it down a little bit will definitely increase your chances of success. A birdhouse that is too small or too large can discourage nesting attempts.
Cleaning Access
To maintain a clean and hygienic birdhouse, incorporate a hinged front door or removable roof. Trust me this will make life so much easier ! This will allow you to easily clean out old nesting materials and debris. Regular cleaning can help prevent the spread of diseases and parasites. 