Which style of birdhouse, or nest box will be the best for attracting wild birds? Below are 4 elements to consider when buying or building a birdhouse.

1. Materials

Wood and Alternative

If made of wood, a nest box should be made of untreated wood, preferably cedar, cypress wood, or pine. Pressure-treated, stained, or painted wood can contain toxins deadly to birds. Acceptable alternative materials include concrete-mixed sawdust, breathable plastics, or even birdhouse gourds.

Metal

Avoid boxes with large surface areas covered by metal - the metal can heat an interior to deadly levels in summer heat. Small strips of metal along the ridge are acceptable, although not preferred.

Hardware

If you want your nest box to last more than a season or two, the screws, hinges, and other hardware used to put the birdhouse together should be of weather-resistant quality.

2. Paint and Other Coatings

A birdhouse should be made of untreated wood - no varnish or protective sealer, etc. -- for the health of the birds. A non-toxic paint in natural colors on the exterior only is acceptable but unpainted is better.

3. Ventilation and Drainage

A quality nest box will have ventilation holes for air circulations near the top edge of the walls and drainage holes in the bottom surface of the nestbox.

4. Design

Look for the following:

• Interior dimensions of at least 4" by 4" and a height of a least 5" to provide room to grow and disance from predators, with walls at least 3/4" thick
• Rough interior walls or walls with carved grooves to provide footholds for the wild birds inhabiting the box
• A roof that extends over the sides of the birdhouse, especially over the entrance hole, to prevent rain from penetrating the box, as well as a recessed floor to keep the nest from getting wet
• Hinged sides or roof for easy access for cleaning
• An entrance hole of the right size for the birds you want to attract (a smaller hole can discourage larger aggressive birds like starlings)
• No perches offering predators access

More Information

Many articles exist covering good and bad characterisitcs of birdhouses. Unfortunately, you rarely know whether the writer is an expert or not. The following links are from the Cornell Lab of Ornithology's All About Birds site. The information found will back up and support the list you see above.

• A picture of important features from Cornell
  
• Nest Box Basics from the Cornell Lab of Ornithology's "All About Birds"
  
• Resources for Nest-Box Monitoring, also from Cornell