Birdhouses should be cleaned out after each nesting — the old nest being removed.
Painting – Outside, Yes, but Inside – Never!
Do not paint or treat the inside of your birdhouse. If you want to preserve the exterior of a pine birdhouse, you can mix a little brown or green oil-based paint with linseed oil. Also, there are two Cuprinol wood preservatives, clear (#20) and green (#10), that are EPA-approved for contact with plants and animals. Never, repeat, never use any lead-based alkyd paints or Creosote. Bright colors should be avoided – they are not attractive to most songbirds. Brown, tan and gray are very pleasing to birds and blend in with the natural environment. However, the exterior of purple martin houses should be painted white to reflect the sun’s heat and help lower the interior nesting compartment temperature. Never paint or treat the interior of a martin house.
Ventilation and Drainage
Make sure all birdhouses have good ventilation. Drainage is also important. For both, check out a prospective house for appropriate tiny holes that insure these features.
To keep predators, such as raccoons, out of a birdhouse, it’s best to try to make the access to the house entrance hole difficult for paws to penetrate. The best way of doing this is to mount blocks of wood, 1-1/4 inches thick, entirely around the entrance to the nest box. This helps prevent raccoons from reaching deep into the house.
Cats & Raccoons
Another cat and raccoon deterrent to pole-mounted birdhouses is to install a post baffle, either the cylinder type, the flat-disc metal type or the clear Duncraft plastic baffle. You may also improvise with a two-foot length of four-inch diameter galvanized stovepipe, aluminum downspout or PVC sewer pipe. Be sure to close off the top of the improvised baffle to prevent access for climbing snakes and mice, also predators of nestlings.