How can I discourage predators like raccoons from raiding my nest boxes?

The best predator deterrent is a combination of a smooth, slippery pole on which to mount the box and installation of a predator guard or baffle. Trees, wooden fence posts, and fence posts intended for wire fence won’t even slow down most predators, as all of these provide marvelous toe-holds for climbers, or rough surfaces for snakes. Galvanized pipe or PVC pipe are both slippery, smooth surfaces that most predators will have difficulty climbing. Adding a predator guard or baffle will stop all but the most acrobatic predators. Make sure your nest box is not set up next to a tree or similar object that predators can use as launch pads.