Numerous designs and modifications have been proposed to meet this goal. The perfect box should attract bluebirds or other native birds while being ignored by introduced species such as house sparrows and European starlings. It should also protect eggs and chicks from predators and severe weather. Monitoring the box should be easy to do without disturbing the occupants. Finally, it should be simple and cheap to build and durable.
Some people feel that they have already discovered the ideal nest box.
Others are still tinkering and searching. Each box style has its advantages and disadvantages, which I will discuss along with the results of my research on box styles. These are the boxes most people have seen or built. This standard box design is among the easiest and cheapest to construct. These boxes generally have 4 x 4 inch or 5 x 5 inch floors.