Click here for a list of birdhouse measurements that can be used to determine which type of birds might be attracted to a specific house. Keep in mind that these numbers are just "rules of thumb." Birds never seek housing with the aid of a tape measure. Their instinctive priorities are safety and comfort.

The diameter of the entrance hole is important. The hole should be large enough to accommodate the desired type of birds, but small enough to keep out predators and other unwanted guests. Houses that have more than one hole might look nice from a design point of view, however most cavity-nesting birds do not like to share their homes. An exception to this would be purple martins who enjoy "apartment" dwelling.

It's a misconception that birdhouses should have a perch. Most birds do not need a perch to access the entrance hole. It only provides a convenient place for predatory birds to sit and stalk the vulnerable fledglings.

If you'd like more information about birdhouses and birdwatching, check out www.bcpl.net.