The breeding of ostriches for their feathers, however, may be regarded as a permanent industry, for there will always be a demand for ostrich plumes, but it cannot be developed as extensively as if the product were a staple article of food. The ostrich farms in America are mostly special farms devoted exclusively to ostrich breeding. Most of these farms are owned and operated by companies. Some of them are stock speculation projects. In South Africa the industry is more in the hands of the general farmers, each of those engaged in it growing a few birds. The people of South Africa have tried to secure a monopoly in ostrich feathers by prohibiting the exportation of ostriches and by purchasing the best stock to be obtained in North Africa. Ostrich farming is practical only in tropical and semitropical countries; the plumage of the birds is too scanty to protect them in the cold winters of temperate climes. In the United States nearly all the ostrich farms are in Southern California and Arizona, but there are some in Texas, Arkansas, and Florida. =Management.= In the places where ostrich farming is carried on, the birds need no shelter. They must be kept in inclosures fenced as for cattle. As ostriches are bred for their plumage, and that of the male is most valuable, the breeder does not object to their following their natural inclination and mating in pairs, but many males are so injured in fighting that they must be killed. This leaves an excess of females, and so two or more females are sometimes mated with one male. The birds are mated for breeding when they are about three and one-half years old. The object of mating them before they are fully mature is to prevent them from selecting for themselves partners contrary to the ideas of the breeder. Each mating must have its own yard, unless the place where more than one family is kept is large enough to allow each family the exclusive use of a part of it. Under such circumstances each group will keep to its own range. The natural food of the ostrich is grass and the leaves of shrubs and trees. In domestication it is usually pastured on alfalfa, or fed on alfalfa hay, according to the season. The alfalfa is often supplemented with grain (principally corn), and grit, bone, and shell are provided as for other birds. Most ostrich growers prefer to hatch the eggs in incubators, because by removing the eggs from the nests they induce the hens to lay more, and because the young ostriches are much easier to manage when by themselves than when with the old birds. When a pair of ostriches hatch their own eggs, the hen sits during the day and the cock at night. The period of incubation is six weeks. [Illustration: Fig. 182. Flock of ostriches on a California ostrich farm. (Photograph from the Bureau of Animal Industry, United States Department of Agriculture)]