But birds are very sensible people. They do not pack a valise or a great trunkful of clothes when they go on a long journey. They have one good travelling dress, and they keep that tidy. When they get to the end of their trip, they do not have to annoy their friends with baggage. Probably their visit is all the more welcome. And their visits are usually short. It seems as if they do not want to wear out their welcome. Of course you have wondered how birds travel, never needing a street, or a railroad track, or a bicycle, or a boat. Perhaps the birds wonder, too, how it is that we never take a flight up into the blue sky, or rest ourselves in the trees, always keeping on the ground in the grass or dust, or in our houses. Perhaps they puzzle their tiny brains to know how it is that we can walk so far without getting tired, and how it is that we are obliged to climb a tree on all fours, like a bear or a squirrel, if we wish to get the nuts which are far up out of reach. There is no telling what the birds think about us. The same Great One who made the birds with hollow bones and quills, and who filled many little cells of their bodies with air, so that the little creatures might be light of weight and buoyant to fly, also made us of heavier weight and greater strength of muscle. The birds are not inventors, but man has invented the steam-engine, and the bicycle, and the sail-boat, so that we have come as near flying as we possibly can without being birds. Almost every boy tries to fly, and he thinks there is some secret about it which he can find out, if he is only patient enough. He gets up on a high fence, and he flaps his arms for wings, and he plays that he is going to fly to the next town. The birds, looking on, must laugh heartily. Perhaps if the boy's body were boat-shaped, like a bird's body, and if his legs were put midway between the two ends of his body like a bird's legs, the boy would come nearer flying. But more than all, he would need a good strong pair of wings. We have never seen a boy yet who had wings of any sort. [Illustration] CHAPTER XV. CRADLE MAKING. There is a good deal said and written about the way birds build their houses. But, really, birds do not build houses. Their houses or dwellings are built for them by Mother Nature, and are the trees and the bushes, and the sheltering rocks and the caves, and the cornices of our own houses. What birds really do build are their cradles,--little crib beds, sometimes with rockers and sometimes without. Birds do not make the cradle first and put the rockers on afterwards, as a cabinet-maker would do. They first choose the best rockers in the market, and then make the cradle on top of the rockers. Sometimes they do a very queer thing; they find the rockers, and then build the cradle under them. Birds have ways of their own, and they are very good ways, as you shall see.