Build the birdhouse out of wood, evoking natural tree nests. Cypress and
cedar are prime options, pine a less expensive choice.
On the inside walls and floor, make sure to avoid wood treated with stains
or chemicals that could harm hatchlings.
Leave those sections unsanded and unpainted, so that nestlings can
eventually clamber out and test their wings.
Painting the exterior will help the birdhouse last longer and allow for
some fun designs.
Flat roofs are a no-no and be sure to build a long eave (three inches
minimum) so that water doesn't dump onto the entrance hole.
Besides the primary entrance hole (that varies depending on the feathered
resident), drill several extra smaller (1/4 inch) holes in the floors and walls for
ventilation and drainage. Also, position the entrance hole away from the area's prevailing
winds, so your birds don't get wiped out during storms.
Be sure to protect birds from animals such as squirrels, cats or raccoons
who will fight the birds for food, or worse yet, kill them outright. Mess this up and
you've build a birdtrap, not a birdhouse.
It's best to mount the house on a metal pole that's cemented into the
ground. And keep it a solid six feet off the ground, well out of cat-leap range. Smearing
the pole with slippery substances like petroleum jelly and hot-pepper spray will foil
climbing attacks.
Build the house so that the top lifts off or unscrews for easy cleaning.
You'll want to check periodically for insect invasions, dampness and other problems.
Finally, if you build more than one birdhouse, distance them from each
other to avoid the natural turf wars that can break out under cramped conditions.