Most, if not all, of these birds are remarkable for the peculiarity of their incubation. Many females unite in the occupation of a single nest, in which a great number of eggs are laid, which are sat upon chiefly by the male; who, when disturbed, feigns lameness, an artifice common to birds which nestle on the ground. The hind toe is wanting in all the genera, except the singular Apteryx of New Zealand, where it exists in the form of a small rudiment.
Family I. Struthionidæ.
(Ostriches.)
The Ostriches are birds of gigantic size, with the neck and legs greatly developed in length. Their plumage is peculiarly lax and flexible, the barbs being decomposed, very fine, weak, and permanently separate, instead of hooking into one another in that manner which gives so much firmness to an ordinary feather. The elegance of the soft, broad, and gracefully curved plumes of an Ostrich's wing and tail is well known and universally admired. In some genera, the barbs of the feathers are so slight, that the plumage resembles coarse hair. The wings are small, or rudimentary; the thighs remarkably stout and muscular; the leg and tarsus are very long; the toes are three, or in one genus only two, and in the latter case, but one is furnished with a nail somewhat resembling a hoof. The beak is rather short, and horizontally flattened, the tip rounded; the tongue is short and of a crescent form; the eye is large and full, and the lids are furnished with long lashes.
