A neighbor erected a luxury bird condo on a tall pole attached to his fancy brick mailbox. He can raise and lower the bird condo the same way people raise and lower flags.

Right now all the doors to the condo's 12 living units are shut. My neighbor said he will not open the doors until the right sort of bird applies for admission. He does not want diversity in his bird palace on a stick. He wants purple martins.Purple martins, I am told, make better neighbors than do English sparrows or other birds that might want to take advantage of my neighbor's extravagant bird abode.

For one thing, purple martins have a prodigious appetite for mosquitoes, flies, beetles, ants and other bugs. This industrious quality is why so many farmers, gardeners and homeowners go to the trouble and expense of erecting beautiful homes for purple martins.

In addition, purple martins provide their ground-based bipedal friends an entertaining aerobatic display as they engage in their chosen profession, which is survival through bugs.

How, I asked my neighbor, will the purple martins be able to take up residence if the doors to 12 living units are shut to keep out undesirables?

This is accomplished, my neighbor said, by watching for the arrival of the martins. He said they will spot the shiny, new residence from aloft, swoop down and alight on the roof. I imagined an activity similar to prospectors planting stakes in the ground during the gold rush.

When the purple martins arrive, my watchful neighbor will lower the bird house and open the doors to welcome his new tenants.

I am at a loss to understand how purple martins recognize this miniature human habitation on a pole as a desirable place to live and raise a family.

Should our roles be reversed and purple martins want to attract migrating humans to their property to take advantage of some human trait I cannot imagine, it's difficult to believe that we humans would want to move into a human-sized version of a martin's saliva, grass and twig nest. Then again, in the right location with plenty of street appeal and a view, who can say? Particularly if it were free.

My neighbor says purple martins will return to the same bird house year after year. This must mean that all new martin tenants will be newlyweds who recently got married in Venezuela and honey-mooned in Costa Rica in preparation to moving into their first home.

The martins should be arriving any day now after wintering in Central or South America, unless El Nino messes up their travel schedules. El Nino has thoroughly confused the plants in my yard.

Purple martins, I've been told, mate for life, which is interesting when you consider that half of all human marriages in the United States end in divorce. You wonder if we could learn something from purple martins.

While I ponder that problem, I'll keep a lookout for the arrival of 24 new purple neighbors on a pole.