Although there are many ways to add ventilation to a hive—and there is much room for beekeeper creativity—several issues should be kept in mind. These include predators, robbing, rain, and cross drafts.
Predators include other species that feed on honey bees, bee larvae, or honey stores. For example, in many areas yellow jackets will take any opportunity to invade a hive and eat both bees and honey. Any opening that is not screened—even the main entrance—is an invitation for these aggressive insects. For this reason, a shim placed under one end of the telescoping cover or between honey supers is usually not a good idea because it is almost impossible for the honey bees to defend so large an area.
Robbing bees present a similar problem. In the late summer when nectar flows are in short supply, robbing bees will invade poorly protected hives and take every last molecule of honey. Both robbing bees and yellow jackets can be so persistent that even the main entrance has to be made small enough to be easily defended. This makes ventilation all the more important. In many areas—such as here in the Puget Sound area—robbing, yellow jackets, hot weather, and nectar dearths happen all at the same time.
Ventilation openings also have to be protected from rain. Especially in the winter, a poorly designed ventilation port can cause water to enter the hive and increase—rather than decrease—the amount of moisture that has to be removed.
Another winter consideration is cross drafts. For example, a draft that goes from the center of the lower front to the center of the upper back will flow right across the winter cluster. Many beekeepers recommend that the air flow be directed along the sides of the hive instead of through the middle.
All of these potential problems can be handled with a well-reasoned ventilation system. In future posts I will present some of the solutions used by other beekeepers.