How do I build birdhouses that attract birds?

I use all sorts of wood scraps and recycled materials to make houses and feeders for songbirds. Some of those projects attract flocks of feathered visitors, but others don't. What can I do to improve results?
—Dan Polson, Durango, Colo.

The material you use and how you treat it can have a big impact on whether a birdhouse or feeder will appeal to its target audience, Dan. For better visitation, try these pointers:

■ Like us, birds prefer to stay out of the heat in the summer and the cold during winter. So don't use plastic decking that gets hot in the sun. Tin and other metals also heat up in a hurry and provide little insulation.

■ If possible, don't place a birdhouse in direct sunlight. Of course, some species, such as bluebirds, require houses out in the open. For those, make walls and roofs from two wood layers, with a ventilating space of 1" or so between the layers. At the least, provide ventilation holes near the tops and bottoms.

■ Thick, solid wood insulates well. Woods that stand up best to Mother Nature include cypress, cedar, redwood, and white oak.

■ Avoid treated wood, which could prove hazardous to birds. For the same reason, stay away from pallet wood, which may have been chemically treated.

■ Resist the temptation to gussy up your birdhouse or feeder with paint, stain, or other finishes. Birds don't like the residual vapors, and dark colors will amplify the sun's heat. Birds also prefer structures that blend into surroundings rather than attract attention from predators. If you can incorporate bark, branches, or other natural wood features into the project, all the better. On feeders, bark and branches help birds feed on the seeds.

■ Staying with the natural theme, avoid sanding the wood. Rough surfaces help adult birds cling to the side of a box when bringing in nesting material or feeding young. And the fledglings will find it easier to scramble out for their first flights.

■ Birds enjoy a tidy house, so include drainage holes in the floor. And allow a means to clean out the house after the nesting season. Scrub down the interior with a solution of one part bleach to nine parts water.

■ Finally, always remember to build and position a birdhouse to minimize the amount of rain that can get through the entrance hole. An overhang helps, as does making the hole no larger than necessary. Online, you can find many charts showing best hole size (as well as interior dimensions) for many bird species.