But some time after another farmer pointed to the rooks in his field, where the corn was green. "See how they be pulling up they young oats," said he. And so they were. But when we looked at the plants which they had pecked up, we found that each one had a place in the root where a grub had been living.

This time the rooks had been doing useful work. Wire-worms and other grubs eat away the roots of grass, corn, and turnips all across a field. When the rooks kill a few grubs, they often save the whole crop.

Once, a long time ago, some Devonshire farmers gave a large reward for rooks' heads, thinking they did harm to the farms. All the rooks around were soon killed. But the farmers were sorry afterwards. During the next three years all their crops were destroyed by insects and grubs. They had to persuade some fresh rooks to build in their neighbourhood to keep down the insects.

No doubt rooks do some mischief, for they eat birds' eggs, and newly sown corn, new potatoes, and green walnuts. They even sometimes pull grain out of the stacks, when they are short of food. But they destroy so many wire-worms and grubs, snails and slugs, maggots and insects of all kinds, that they do more good than harm.

You all know the heavy whirring cockchafer, which flops into your face in the evening. But perhaps you do not know that before he had wings he lived for three or four years underground feeding on the roots of grass and corn. Rooks eat these cockchafer grubs wherever they can find them, and so save our crops.

I hope you have rooks near you, for they are delightful to watch. When they build their huge nests high up in the forks of trees, they make a great deal of noise and bustle. The father-rook begins to fetch food for his mate even before she lays her eggs, and feeds her all the time she is sitting.

The old birds feed the young ones long after they are hatched. If you watch, you may see the young ones sitting on the edge of the nest opening their mouths to be fed. Rooks like to build near old houses, and use the same nests year after year. They will not allow strange rooks to join them.

If the trees in which they build lose their leaves in winter, the rooks do not stay there long after the last young ones are able to fly. About August or September they often go to the beech and pine woods to sleep, and do not come back to their rookery till the spring. But every now and then on their way to and fro they call at their rookery and look after their nests.

Crows do not live together in numbers like rooks. They live in pairs, and build their nests in the top of some high tree away from houses. They are more mischievous than rooks, for they feed on birds and young lambs, young pigeons, ducks, or chickens.

You may tell a crow from a rook at a distance because you very seldom see more than two together. When you can see them near, you will know them apart, because the rook, after he is a year old, has a bald patch on his head just above his beak, where the crow has feathers.

Have you ever noticed how gravely a rook walks across a field? He does not hop like a thrush or a sparrow, but moves one foot after the other, and gives a little jump every now and then. One or two always remain on the trees near, to give notice of danger, and when these sentinels cry "caw-caw" the whole flock rises. They fly away, flapping their wings slowly, and drop down one by one in another field.

A friend of mine who lives near a rookery says she often sees from her window one or two sentinel rooks go round every morning and wake up the others, and it is very funny to see how the lazy ones scramble up in a great hurry at the last, so as to be in time to fly away with the rest.

Though rooks will not allow another party of their own kind to join them, they allow starlings, jackdaws, and fieldfares to feed with them. A Jackdaw moves much like a rook, though he is a more sprightly bird. He is smaller and has a grey patch on his head. The Starling (see  p. 53) is a walking bird. Though his head and back are black, he has so many bright colours on the tips of his feathers that he does not look so dark as the rook and the jackdaw, but very bright and gay.

I wonder why these birds like so much to follow the rooks? Perhaps it is because the rook has a keen scent, and turns up the earth for food with his long beak. The jackdaw and starling only pick up what they find above ground, so when the rook turns up the earth, they may get some of the food.

Try to see a rook, a crow, a jackdaw, and a starling, a magpie and a jay, and point out how you know them apart.