Terry Wilson, age 11, of Sylva, North Carolina, for his question:

What kind of bird is the purple martin?

Each one of nature's creatures has at least one human friend. Some of us love snakes and others love spiders. But almost all of us love almost all of the birds. Maybe we are annoyed by the handsome bluejay's aggressive thievery and perhaps we fail to appreciate the useful qualities of the turkey buzzard. But everybody loves every¬thing about the purple martin. Everybody, that is, except a few soreheads who have only a minimum of human affection for their own requirements.

The martins are swallow type birds and the purple martin is our most popular summer visitor. His body is larger and chunkier than that of the elegant barn swallow. His tail and his wings are shorter and somewhat less slenderly forked. The glossy plumage of the male bird is bluish purple and he darts through the summery air like a flying jewel. From his sturdy beak to the tip of his stubby swallow tail, he measures seven and sometimes more than eight inches. The female purple martin has a modest, greyish vest and so do the youngsters, both male and female.

In the fall, these beautiful birds depart to spend the winter way down in Central and South America. In March and early spring they begin arriving back north for their nesting season. They spread out from coast to coast as far north as Saskatchewan in Canada. Sad to say, they avoid a region of the western mountains north of Arizona. The same birds return to the very same nesting place year after year. And wherever they visit, the purple martins are welcome.

Of all our nesting visitors, these birds are the most friendly toward us. They seem to like people and they certainly feel that we can be trusted to treat their precious youngsters with kindness. Most birds shy off and hide their nests in secret places. The purple martins actually prefer to nest in bird houses made by human hands, right close to human habitations. Bird fanciers construct a wondrous assortment of fancy homes for them    and the purple martins know just what they are for.

However, when building for purple martin tenants, we must remember one important fact. We must build a bird apartment house    for these charming creatures nest in colonies. The house may be a human type house with windows and colonades    the fancier the better. It must have plenty of separate rooms for plenty of nests, each with a window which will be used, naturally, as a door. The finished residence is  fixed on a post, well above the reach of cats. It is only fair to make sure that your bird apartment house is securely built and weather proofed and that the sturdy post cannot be jogged or toppled.

The handsome bird tenants will perform useful duties to reward you for your trouble. Naturally, they pay no rent. Instead they gobble up all the flying insects within range. Your garden, which is also their garden, is picked free of flies and beetles, flying ants, moths and all the other pesky winged bugs. And this natural bug proofing lasts all summer    until your adult and teenage purple martins depart for their winter residence.

You can watch a lot of interesting family life in your bird house. But you would not wish to disturb the quiet nests inside the apartments. For your infor¬mation, the nest is built of grasses, straws and twigs. Mrs. P. Martin lays four or five sizeable plain white eggs. When these birds live far out in the wilds, they build their nests either in little cliff cavities or in small holes in high tree trunks. And even in the wilds, several families nest close together.