It is odd how many birds build on or near the ground, which you would think was dangerous. The robin is particularly fond of this; it chooses an overhanging bank if it can find one, and though the nest is well hidden, there is nearly always a cat prowling near to seize the young ones just when their first feathers are growing, so it seems wonderful that robins ever escape at all. On the left side is the wood-wren, with a nest just like a handful of hay flung down among some dead leaves. Near here, too, are the house-martins, and further on the swallows and other birds, who build under the projecting eaves of houses; of all the nests, these look the most safe and cosy. The house-martin is a really clever builder; he takes little mouthfuls of clay in his beak and sticks them one by one under the deep overhanging tiles or slates of a house or barn, and gradually forms a complete nest like a ball of clay, which dries hard, and is stuck against the wall, with only one opening like a lip at the top. The nest does not look comfortable, but it is, for inside it is lined with the softest white feathers, whereon are laid the pearly-white eggs. The sand-martin, the house-martin's cousin, prefers the side of a cliff. He digs into a cliff or sandbank a long tunnel quite as long as your arm, and just big enough for him to pop in and out with comfort. At the very far end of this in the warm darkness he puts bits of straw and feathers to make a bed, and here the young are hatched. Until they grow older they never go down that long mysterious tunnel where mother and father run in and out, but only see in the distance the white gleam of a round hole. What a wonderful world it must seem to the young bird when he first steps out! He is very timid, and as he gets near the opening he hears the beating of the waves on the shore perhaps, and then the great wide ocean opens before him and the illimitable sky. What a big world! He must turn almost giddy with fright and amazement. Some birds choose furze-bushes to build in, which must be prickly and uncomfortable, but are thick. Here there is a woodpecker family. The woodpecker is a fairly big bird, and he has a beautiful crimson streak on his head; with his strong bill he carves out a deep hole in a tree, right into the trunk--it is wonderful that the bird should have the strength and patience to cut into the solid wood--and when he has made a deep hole, he begins to make it bend down, and in the dip he makes his nest. The young woodpeckers are therefore shut in very tightly and safely. The parent birds run up and down the trees seeking for insects, on which they live. To see them run straight up a tree as a cat would do is very curious; but they are shy birds, and not often seen.