Protect Your Birdhouses from Predators

Cats  

Nesting birds are very vulnerable to cats, as are fledglings and birds roosting for the night. Bell collars on cats offer little protection for the birds. Nailing a sheet metal guard or cone to a tree trunk is unsightly, but it may deter less agile felines. Birdhouses mounted on metal poles are the most difficult for predators to reach, especially if you smear the poles with a petroleum jelly and hot pepper mixture.

Dogs

Pet dogs are a hazard to nestlings in the spring and summer. All it takes is one swift bite and the baby bird is gone. Don't let your dog run loose during nesting time.

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 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 predator guard to the bird house or to its pole support is a simple solution.

Snakes

Snakes are an important part of the natural balance between predator and prey. If you find one of these reptiles in your bird house, please don't kill it. Snake-proof your house by putting it on a metal pole lathered with vaseline or hot red cayenne pepper.

House Sparrows and Starlings

If you don't discourage them, these two pest species introduced from Europe will bully 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

Sometimes house wrens interfere with the nesting success of other birds by puncturing their eggs. But unlike the sparrow and starling, these birds are part of the natural system. They are protected by law. Don't be tempted to intervene.

Insects

Many insects lay their eggs and pupate in bird houses. You should inspect your birdhouses for signs of gypsy moths, blow flies, wasps, ants, gnats, and bees.  You can 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 are favored by the gypsy moths.

Pyrethrin and rotenone insecticides are recommended for killing fly larvae and bird lice after birds have finished nesting for the season.