Diana. Kidd., age 12, of Oskawa, Ont., Can., for her question:

Why don't birds have teeth?

Purple cows and black rainbows are as scarce as hen's teeth  which is to say that they do not exist at all. But the remote ancestors of our bards did have teeth, and they were very capable teeth. As the bird world developed, however, teeth went Out Of Style, and so far as we know all the birds have been toothless for at least 60 million Years.

The robin dines on juicy worms, and the purple martin zooms through the air catching flies and moths. The kingfisher devours frogs and fish  bones and all. The bobwhite and the pheasant, the various sparrows and pigeons feed mostly on tough grains and weed seeds. Some of this food, you would think, needs chewing. But eyery bird is tooth1ess, and each bite must be swallowed whole.

Hawks and other birds of prey have sharp bills and claws which they use as knifes and forks to cut their food in bite size morsels. A robin sometimes treats a long worm like a string of spaghetti and swallows it down inch by inch. But most birds gulp dawn seeds, insects and other smallish items in single mouthfuls

A bird as a rule has a long neck, and the food passes into his long throat or gullet. About halfway down his gullet he may have a small pocket called the crop. This is a sort of storage room where food is kept before it goes down to the true stomach to be digested. If you gulp mouthfuls of unchewed food, your stomach rebels, for it is not built to cope with tough lumps of food.

    But a bird's stomach is all ready to cope with this problem. It is a tough, hard muscle called the gizzard, and it squeezes together like a leathery fist.  The lining is so sturdy that the gizzard is not torn by bones and gritty grains.

Sometimes, however, the gizzard needs help to grind up the food into the kind of juicy pulp which the bird's body can digest. This is why you sometimes see a bird swallowing a small pebble or a piece of gritty gravel. These indigestable items go into the gizzard, which uses than to grind and mash the bird's dinner into soupy pulp. So, a bird has no teeth, because his chewing is done for him by his gizzard.

A bird. Is always on the go and rarely has time to sit down to a full course meal. He is a snack eater, always nibbling. This means his digestion is always busy, and it explains why some birds need a crop to store the next snack until his gizzard has finished with the last one. Nevertheless, birds devour a lot of food. If you ate as much as a pigeon, you would need nine full size meals every day.