An ant moat is a device designed to keep ants from getting into bird feeders. They are most commonly used for hummingbird feeders, due to the sugar content of the fluid inside.
Ant moats work by preventing the ants from climbing all the way down to the feeder by using a trough of water as an impassable barrier. They must be maintained regularly, however, as debris or evaporation can prevent the moat from being effective. Ant moats come as built-in features in several models of feeder. While ants themselves do no damage to the birds or feeder, the addition of a moat can keep feeder maintenance down and discourage the growth of nearby ant colonies.