Think of the delight children and adults both experience when they watch birds building their nests, and the awe they feel when they spot the first fledglings peeking out, then learning to fly! Erecting a properly designed nest box promises not only education and entertainment, but the potential for significant increases in local bird populations.

At least 22 resident Florida birds nest in cavities in trees or branches. Some do their own excavating, but most depend on natural cavities chiseled out and then abandoned by woodpeckers. If you think natural nesting cavities are scarce in your neighborhood, you should supply artificial nest structures.

When buying or building a bird house, make sure it is designed for a specific species-not just for "birds." Commercial boxes are often built more to attract buyers than birds. Keep in mind that each species has preferred nesting requirements (see table). The closer you match these preferences, the more likely it is that your nesting structure will become occupied.

Boxes should be built of 3/4-inch durable woods such as cypress, western cedar or exterior-grade plywood. Use rough-cut grade lumber; it will blend nicely with the natural habitat you are creating and give the birds a foothold when they climb out of the box. Avoid using plastic or metal boxes. They absorb too much heat during our scorching summers and may bake the fledglings. Exceptions to this rule are the anodized aluminum purple martin houses now available. These structures have a relatively large entrance and central ventilating shaft that opens to each compartment and provides sufficient cooling.

A good bird house should:

• Have ventilation holes under roof overhang.

• Have drainage holes.

• Have cleats or be roughened with a wood chisel beneath the entrance hole to help birds climb out.

• Be built for a definite species; proper entrance size and cavity depth very important.

• Have roof extending over all sections for maximum protection.