“The orthotomus, or grass-warbler, a small bird of India, is an even more skilful tailor, and in fact is commonly known as the tailor-bird. It selects two large leaves, still living and attached to the branch on which they grew. These are brought together, with their longer edges touching, and are sewed border to border with strong cotton thread made by the bird’s beak. The seams run only half the length of the leaves, in such a manner that the two together, hanging down as they do, form a conical sac with its mouth upward. In this sac the nest is placed, hidden by its protecting envelope, which so blends with the rest of the foliage that even after a person has once found the nest he can with difficulty find it again. “In South Africa there is a bird scarcely larger than our swallow and known as the social republican from its living in large societies with one nest in common. This nest, a sort of bird village, is shaped like an enormous mushroom, spreading out all around the trunk of a tree, which serves as its stalk, while the lower branches also furnish their support. This colossal edifice is of such bulk and weight as to make a wagon-load, and if one wishes to see the interior structure it must be chopped to pieces with an axe. It is formed wholly of dry grass arranged much like the thatch on our rustic roofs. “Indeed, this structure, built at public expense by all the associated birds, is nothing but a roof, a dome, destined to shelter the real nests, which are attached to the inside of the thatched covering. Here are to be found a multitude of round holes presenting all together somewhat the appearance of a honeycomb. Each hole gives access to a small cell, a veritable nest and the separate work of a single pair. The grass roof, then, is built in common by the whole society, after which each family provides for its exclusive use a little apartment attached to the lower side of the roof. The number of inhabitants may reach as high as a thousand.” CHAPTER LVII MIGRATION OF BIRDS “At the approach of the cold season,” Uncle Paul resumed, in his account of bird habits and bird peculiarities, “before winter clears the fields of insects, covers the ponds with a coating of ice, and whitens the landscape with snow, thus cutting off the food-supply hitherto obtainable from the earth, many birds, especially those that live on insects or frequent bodies of water and marshy meadows, take leave of their native land and direct their course southward, where they will find a warmer sun and a more assured supply of food. “They take their departure, some in large flocks, others in small groups, or even each one separately. With no guide other than an irresistible impulse too mysterious for us to explain, they traverse by successive stages immense tracts of land, cross seas, and bend their course toward the countries of the south. Africa is the rendezvous of our birds and of European birds in general.