The Garden Bug: Safer Bird Houses
By Brenda Weaver
Birds may reject a birdhouse placed near food or water, as these attract raccoons and rats that will eat birds and their eggs.
Claw marks on the house's surface or nesting material pulled from the entrance will show you these predators are around and can easily reach the birdhouse.
Try mounting the house away from food and on a metal pole, rather than on a tree trunk or hanging it on a branch. Smear the pole with a petroleum jelly/hot pepper mixture and spread sharp gravel around the base to discourage intruders.
Source: www.all-birds.com