Page:Natural History, Birds.djvu/261

 (Running-birds.) In the Poultry we have seen the power of flying, so characteristic of a bird, reduced to a feeble and imperfect condition; we come now to species in which it is totally lost, the wings themselves in some being reduced to mere rudiments. On the other hand, as the reduction and gradual extinction of one set of organs are frequently connected with the increased development of another series, in some respects correspondent, so here we find the posterior limbs increasing in size and muscularity with the decrease of the anterior. The pectoral muscles are small and slender, and the breast-bone (sternum) presents an uniform convex surface, like that of a shield, utterly destitute of even the rudiment of the keel, which is so large and prominent in the Swallows, Humming-birds, and other powerful fliers.

The Runners are all large birds, most of them equalling, if not exceeding, the average height and bulk of the Mammalia, to which indeed they exhibit a closer approximation than any other of the feathered tribes. The single Family in which they are all included (for the Bustards seem to be more allied to the Waders, and the place of the extinct Dodos is yet doubtful) is almost confined to the Southern Hemisphere, one species alone reaching to the north of Africa and Arabia. They chiefly inhabit immense plains.