Kenneth Lewis, age 12, of Houston, Tex., for his question:

What are the main bird groups?

Most birds are delicate looking creatures. They amaze us with their ability to cope with the weather and other hardships of outdoor life. They are smart, and most of them are handsome. After the chores of making a living and rearing a family, many birds find ume to sing.

Our knowledge of the bird world grows as scraps of information are gathered by clubs and countless lone observers. Bird watching is a fascinating hobby, and a quiet observer is rewarded with endless glimpses into the wondrous ways of nature. Sooner or later he wonders about the total picture of the feathery bird ttorld. He wants to know how many different birds there are and how the experts classify them.

The job of classifying the birds is done by the ornithologist, and most of the scientific names he uses carry hidden clues to the birds in each group. Quails, chickens, pheasants and peacocks are classed as galliformes, a term coined from an older word for the chicken. Hawks, falcons, vultures and eag1es arefalconiformes because all members of this group share features with the falcon.

We know of almost 30,000 different varieties of birds, and they all belong in the animal class ayes, meaning birds. The huge class is subdivided into orders, and the birds of each order share certain common features. The ones in the falconiforme order have hooked beaks and are birds of prey.

Ornithologists classify birds in about 30 separate orders. Ducks, geese, swans and other wide billed, web footed water birds have their own order. The Charidiiforme order includes the gulls and other web footed waders and shore birds.

The round eyed, night prowling owls belong in the order strigiformes. You can look up the meanings of these terms in a big dictionary that politely includes the origins of its words.

More than half the different birds are passeriformes. This popular order belongs to the birds with special perching feet, and many of them are sweet songsters. The 30 or so bird orders are subdivided into families and again into genera. Each genus, the singular of genera, is a small group of individual species and subspecies.

The birds of a species are as closely related as brothers and sisters, and there are 8,600 separate species. The members of a species, however, may be marked differently. Our western robin wears a dark necklace around his red throat. The western and the plain red vested eastern robin are classed as varieties or subspecies.

Ornithologists classify the known birds in almost 30,000 separate subspecies.