Protection from Predators Bird House Selection House Placement Birds you can attract Materials Design Nesting Box Chart Bird Feeders Landscaping for Birds Home Wren & Chickadee House Cats Nesting birds are extremely vulnerable to cats, as are fledglings and birds roosting for the night. Bell collars on cats offer birds little protection. Nailing a sheet metal guard or cone to a tree trunk is unsightly, but may deter less agile felines. Houses mounted on metal poles are the most difficult for predators to reach. Avoid using grease or petroleum jelly on the pole, it can get on the bird's feathers, and not being able to preen it off can be fatal. The best deterrent is for owners to keep their cats inside whenever possible. Squirrels Red squirrels, and sometimes gray squirrels, can become a serious menace to bird houses and the birds themselves. If you find your nest hole enlarged, chances are a red squirrel is the culprit. Once inside the box, squirrels make a meal of the eggs and young. Adding a predator guard made of sheet metal to the entrance hole is usually enough to keep squirrels out. Raccoons and Opossums Raccoons and opossums will stick their arms inside nest boxes and try to pull out the adult, young, and eggs. Adding a 1/16 inch thick predator guard to the bird house or an inverted cone to its pole support is a simple solution. Snakes Snakes play an important part in the balance of nature. If you find one in your bird house, don't kill it. Snake-proof your house by putting it on a metal pole with squirrel baffle. House Sparrows and Starlings If you don't discourage them, these two nuisance species introduced from Europe will harass or kill cavity-nesting birds. Since house sparrows and starlings are not protected by law, you may destroy their nests. But remember, other birds are protected by law. House Wrens House wrens sometimes interfere with the nesting success of other birds by puncturing their eggs. But, unlike the house sparrow and starling, these birds are native to North America and are protected by law. Don't be tempted to intervene when wrens appear at your backyard bird house. Insects Many insects lay their eggs and pupate in bird houses. Inspect your bird houses for signs of gypsy moths, blow flies, wasps, ants, gnats and bees. Keep bees and wasps from attaching their nests by coating the inside of the roof with bar soap. In areas where gypsy moths abound, avoid placing boxes in oak trees, which the gypsy moths favor. Pyrethrin and rotenone insecticides are recommended for killing fly larvae, bird lice and mites after birds have finished nesting for the season.