This fact is simply a part of nature's food chain. This is a part of the chain that one must intervene or a colony can be completely annihilated. Predators can attack a martin colony from the ground or the air. Let's look at a few of them and some of the ways of preventing this misfortune. Aerial Predators Owls, hawks, and falcons are the main predators that attack by air.
Owls are by far the worst of the three.
Being mainly a nocturnal predator, they attack martin colonies late in the evening, night or early morning hours as martins are going to roost, sleeping, and getting ready to leave the colony. Owls usually fly down and lock onto the housing with one claw and beat their wings against the compartment scaring out the martins. As the martins exit the owl will grab the martin with his other claw. Once in the grasp of the owl's claw the martin has little chance of escape. If you live in a rural area, this can be one of the greatest threats to your colony.