There are many different styles of Swiftlet Houses, and there are no fixed requirements. It's just that many things will affect the occupancy rate of swiftlet;
Among them, the size of the entrance hole: the bigger the entrance is, the higher the rate of new birds dare to enter, especially first time visiting the new house.
Note: The large entrance hole will blow in a relatively strong air flow, so the ventilation hole inside needs to be reduced or closed. In addition, predators will be easier to enter, and prevention need to be taken to avoid losses from predators.
Cost: The shape of the house directly determines the investment cost, because this is an investment, so the faster the return on the investment, the more cost-effective it will be.
Height: The height depends on the environment where the Swiftlet House is located; if there are no trees/high buildings nearby, the height of the house itself does not need to be too high.
Color: The dark exterior wall will greatly increase the heat absorption, and the difference can be more than 10 degrees Celsius relative to the white/bright wall.
Control of predators: According to your environment, do a good job of predator control on the outer wall, and don't let predator such as snakes to climb up easily.