Patricia Wong, age 11, of St. Catharines, Ontario, Canada, for her question:

When did the first birds appear?

The feathery bird world apparently arrived in easy stages. Tracing their story back through the ages was not easy. For, like modern birds, these earliest ancestors were lightweight, fragile creatures. On the other hand, the massive dinosaurs left numerous samples of their durable bones to become fossils. The delicate remains of most early birds were destroyed    and the fossil record of their history is very sketchy.

Scientists assure us that our feathery birds are descended from a branch of the ancient reptile clan. Their earliest ancestors were oddities, neither genuine birds nor genuine lizards. For example, instead of beaks, they had long narrow snouts  ¬with toothy upper and lower jaws. They also had claws on their wings. But unlike their reptilian relatives, they had feathers instead of scales and most likely they were warm blooded animals, at least to some degree.

To meet these early birds, we would have to go back to the Jurassic Period of 150 million years ago. The Sierra Nevada was then a young range and the Rockies were unborn. The world climate was mild and moist and the earth was populated by dinosaurs    in a multitude of shapes and sizes. In this ancient world, already the first true birds had spread their feathered wings and mastered their first flying lessons.

The first proof of this came in 1861, when a strange fossil was found in Bavaria. The bones might have been mistaken for the fossil of a chicken sized lizard. However, the complete skeleton in the hardened mud was surrounded by detailed imprints of true feathers. Obviously this was the fossil of a true bird    and he lived about 150 million years ago.

Scientists named him archaeopteryx, which means the Ancient Winged One. Later, the fossils of two of his kinfolk were found in the same muddy deposits. During this period, several bat winged lizards took to the air. They are called the pterodactyls and not classified as true birds. These weird fliers departed with the dinosaurs, about 60 million years ago.

The true birds, of course, survived and multiplied. About 100 million years ago, a very strange waterfowl lived in what is now the state of Kansas. His big webbed

feet were built for swimming and his wings were more suitable for paddling than for flying. He was named hesperonis, the western bird. Some of his kinsolk resembled loons, others were as big as small seals. All of these early arrivals of the bird world had teeth, plus claws on the wrist joints of their wings    and none of them were ace fliers.

As the dinosaurs departed, an assortment of modern type birds chirruped and fluttered onto the scene. They thrived and made themselves at home just about everywhere in the world. All the feathery families of today were well established some 60 million years ago. By that time, teeth and wing claws in the bird world were way out of style.