英文科學(xué)讀本 第三冊(cè)·Lesson 08 Birds

Lesson 08 Birds

Suppose we have a chat about birds this evening, said Fred. "Can you tell me, Norah, why all birds are clothed with feathers?"

Feathers make the lightest of all coats, said Norah. "Birds have to raise themselves in the air and fly, and a thick heavy coat would prevent them from doing this."

Quite right, and so would a thick heavy body, wouldn't it? Teacher has been showing us that the bird's body must be light as well as its clothing.

If we compare the bones of a bird with the bones of some other animal about the same size, we find a great difference. The bones of the bird are very much lighter.

You would find out the difference by holding Will's guinea pig in one hand and my pigeon in the other. I am sure it would surprise you.

The bones of the bird are all hollow, and at the same time they are very light and thin.

Now let us think of the build of the bird's body. We ourselves, as well as the animals about us, have two pairs of limbs. So has the bird; it is built on the very same plan, except that it has wings instead of arms or forelegs.

Teacher made us compare our own arm and hand with the wing of the bird. We have an upper arm, a forearm, and a hand. The bird has all these parts to its limb, but the bones are lengthened to make a wing for flying.

Do you know which part of our lesson pleased me most, Fred?

I suppose you are thinking about the mouths and feet of the birds, said Fred.

Yes, I am, replied Will, "for I can't help thinking that it is very wonderful."

You know, Norah, we learned a long while ago to look into the mouths of animals when we wanted to find out all about them, their food and their habits. The teeth of the animal tell us all we want to know.

Teacher showed us a great many heads of birds. They all have hard horny beaks or bills instead of mouths, but the bills are not all the same shape.

The bill forms mouth and teeth all in one, for birds have no real teeth. We call the two parts of the bills the mandibles.

Teacher says the bills are not all alike, because the birds themselves are not alike in their nature, their habits, or their food.

Just as we learned to do in the case of other animals, so shall we have to do with the birds. We must examine their mouths to learn what we want to know about them.

You remember too, of course, that in all our old lessons we found the feet as important as the mouths. We always examined the feet. Teacher told us today that we must learn to do the same with the birds.

He showed us some pictures of birds' feet. They were all different from the feet of any other animal. We call birds' feet claws.

Although all birds have claws, there are many ways in which the claws of one bird differ from those of another.

Teacher says that in every case the nature, habits, and food of the bird depend upon the form of the claws, as well as upon the bill.

SUMMARY

The bones of the bird are thin, light, and hollow. Instead of arms and hands the bird has wings for flying. Birds have beaks, which serve as mouth and teeth all in one. Their feet are claws; but they are not all alike.