Читать книгу Round the Year with Enid Blyton—Autumn Book - Enid blyton - Страница 4

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Do you remember how we listened for the cuckoo’s pretty double-note in the spring-time? We wanted him to come back because his call told us that spring was really here! We listened to his “Cuckoo! Cuckoo!” in May, we heard him change his tune in June—and then, what happened? We heard him no more!

Where had he gone? And why had he gone? The screeching swifts disappeared too, not long after—and now, one by one, other birds are going away from us or have already gone. The willow-warblers, the nightingales, the sand-martins have all said good-bye, and soon the swallows and house-martins will fly away too, and one morning we shall listen in vain for their musical twittering. We shall see them no more until next spring.

They all fly southward in the autumn to the warm lands where the sun shines brightly and insects are easily found. Get out your maps and see where they go to. Find the Mediterranean Sea, Egypt and Algiers. Look for Cape Town at the very south of Africa. “Surely no bird can fly from England all the way to Cape Town!” someone says in surprise. It is certainly astonishing, but quite true.

It has been proved that a swallow from Northumberland flew all the thousands of miles to Cape Town—and even longer flights have been recorded. Another very long flight, which you can trace on your maps, is that of the Virginian Plover, which flies each year all the way from Labrador to Brazil.

In the spring-time our birds fly back to us, and arrive on our shores eager to nest and bring up their young ones. Where they were born themselves is “home” to them, and so great is their instinct for “homing” that a bird will actually fly back to the same village, and find the same tree or barn, where it had its nest the year before! There it will build, and bring up its young ones, and they, in their turn, will perhaps come back the following year and nest in the same village in which they themselves were born.

SWALLOWS GATHERING ON TELEGRAPH WIRES BEFORE MIGRATING

Not all birds leave us in the autumn. You will be able to think of many that stay with us all the year round. We call these birds Residents, because they reside or live with us. Let us think of some. Sparrows, starlings, rooks, robins, thrushes, blackbirds, tits—we can see these in the winter as well as in the summer. But even these resident birds sometimes travel about to look for better feeding-grounds; the thrushes we have with us in the winter may not be the same ones we had in the summer. They may be thrushes from a more northerly part of the country who have come south because of a cold spell.

And now you will be asking a few questions, some of which I shall not know how to answer. Why do the birds go south? Why do they come north in the springtime? How do they find their way from one country to another? What began their great movement twice yearly? Well, before I try to answer, talk about it yourselves, and see what ideas you have.

How will you answer the question, “Why do the birds fly south?” I think I know. “Because,” you say, “the days are getting cold and food is getting short.” Well, that is correct for, say, the swallows, who leave in October—but what about the swifts and the parent cuckoos, who leave in July, when the weather is hot and insects everywhere?

Why do the birds come north in the spring? I am sure you will say it is because they want to nest in the place where they themselves were born. But why should they not stay to nest in the warm, plenteous region where they live in the winter-time? Why must they go to and fro like this, and seek a summer nesting-place and a winter resting-place? They do not nest in the south—they always come north to breed.

It is a general rule for all birds in our part of the world to nest in the coldest part of their range, and it is a good rule, for the youngsters are hardier and sturdier then. The birds, however, cannot actually know that—something must have happened at a distant time to start the strange habit of world-wide migration. What could it have been?

Well, we do not really know. Some naturalists say that long ago, when the world passed through a very cold age and glaciers spread down from the north, accompanied by bitter winds, all life was driven southwards. The birds migrated easily, because their wings could take them anywhere, and they flew off to the south to seek the warmth and food they needed. Then, when summer came and the sun melted the glaciers, the birds returned as far northwards as they could, striving to nest where they had nested before, only to be driven south again as winter approached. So, say some naturalists, began the great to-and-fro movement of the birds. The habit was started, became an instinct, and, because it proved good for the race of birds, continues down to this day.

This may be all wrong—but, at any rate, we feel sure that at some time or other in the history of birds some great happening began the habit of migration. It is an excellent custom, from the bird point of view, because to come north in the spring-time means warm weather, plenty of food (when the heat in the south may mean parched lands and food scarcity), long hours of daylight in which to look for food for the youngsters, and a hardy upbringing. To go south in the autumn solves the problem of warmth and food at that season.

How do the birds find their way? “Oh,” you will perhaps say, “that’s easy. The old ones lead the way, of course! They remember it from the last year!”

But the strange thing is that the old ones do not lead the way! Except in a few cases, old and young fly away separately. The young ones fly first, and as they have never before left our shores, how in the world do they find their way? The older ones follow later, except the cuckoos, who leave before their young.

Much of the flying is done at night, when no landmarks can be seen, and a great deal of it is over the sea. Some birds fly close to the water, so that, even if they wished to, they could not see their way clearly! How, then, do they know their way half across the world?

We do not know. Birds have a great sense of direction, excellent eyesight, and a wonderful memory for landmarks, but these things cannot alone account for the wonders of migration. The wind helps a good deal, because, in the springtime a south-west breeze blows, and in the autumn a north-east wind. Birds starting out on their long journey fly straight upwards until they reach a strong current in the upper atmosphere, and then fly steadily onwards.

It is a brave, venturesome thing, this long flight to far countries. The weather may be good at the start, but storms, fogs, gales, head winds, blizzards may arise, and then the flocks of tiny travellers are in a dreadful plight. If they are over the sea thousands fall and are drowned. If a ship or steamer is near, the captain suddenly discovers that hosts of little birds have flown to it and are resting in every corner!

WILD GEESE MIGRATING: THEY FLY IN ARROW-HEAD FORMATION

A lighthouse, with its great white beam of light, attracts hundreds of thousands of weary birds in a storm, and they dash themselves to death against the lantern, or fall dazzled into the sea. Many lighthouses have perches round them for the birds, but there is never enough room for the multitudes that seek sanctuary from the storm.

A great many migrants follow the coast-line when flying, or travel down river-valleys. We know this because such flocks have been seen. Other flocks fly so high that we cannot see them with our naked eye, but must use a telescope. We may perhaps hear their call, but to our eye the sky is quite empty! Many birds fly at night, and these have been seen by astronomers who, looking at the moon through their telescopes, suddenly see great flocks of birds in the night-sky, clearly defined against the bright moon. The birds fly about 30 miles an hour, but may speed up to 60 if they are trying to out-fly a storm.

A great many birds are ringed by naturalists when they are young, and it is these marked birds that tell us such a lot about migration. A ringed bird has a light band or ring round one of its legs, and on the ring is an address and a number. Anyone finding a ringed bird should write to the address, and give the number of the bird, and the place and date it was found. We know then how far the bird has travelled. Set the bird free again, of course, so that it may give yet more information if it is caught a second time. I have never found a ringed bird yet, but I am always hoping to.

The swallows will soon be gone this year. Have you seen them collecting yet? Near my house there is an old barn and also some telegraph wires, and the swallows crowd together in hundreds on the roof and on the wires before they go. Then one evening they rise in the air and fly southwards, and the next morning I cannot see a single one. They have all gone, and I shall see them no more until the next spring-time. Keep your eyes open if you still have swallows about, and watch to see if they collect together in your district—and be sure to notice if young and old are together. The young have shorter tails than the old ones and can easily be picked out.

Famous naturalists say that if only people would notice the birds as carefully as they notice the weather, we should soon solve many of the mysteries of migration, so let us make a start this week, thousands of us all over the kingdom, and perhaps we shall, between us, find out something really worth knowing!

THINGS TO DO

1.

Make out a list of all the birds you are sure you will see in the winter.

2.

Look every morning for the swallows. Put down on the Nature-calendar, or in your Nature notebook, the date of the last day you see them.

3.

Draw a lighthouse with many birds flying round it.

4.

Have you any resident bird in your garden with peculiar markings, such as a blackbird with a white feather or two? If you have, watch for it all the year round, and see if it stays with you.

5.

We have winter visitors as well as summer visitors. The fieldfares are winter visitors. Where do they come from, the north or the south?