The rhea, or South American ostrich, philosophers tell us, is a very ancient bird on the earth; and from its great size and inability to escape by flight, and its excellence as food, especially to savages, who prefer fat rank-flavoured flesh, it must have been systematically persecuted by man as long as, or longer than, any bird now existing on the globe. If fear of man ever becomes hereditary in birds, we ought certainly to find some trace of such an instinct in this species. I have been unable to detect any, though I have observed scores of young rheas in captivity, taken before the parent bird had taught them what to fear. I also once kept a brood myself, captured just after they had hatched out. With regard to food they were almost, or perhaps quite, independent, spending most of the time catching flies, grasshoppers, and other insects with surprising dexterity; but of the dangers encompassing the young rhea they knew absolutely frothing. They would follow me about as if they took me for their parent; and, whenever I imitated the loud snorting or rasping warning-call emitted the old bird in moments of danger, they would to me in the greatest terror, though no animal was in sight, and, squatting at my feet, endeavour to conceal themselves by thrusting their heads and long necks up my trousers. If I had caused a person to dress in white or yellow clothes for several consecutive days, and had then uttered the warning cry each time he showed himself to the birds, I have no doubt that they would soon have acquired a habit of running in terror from him, even without the warning cry, and that the fear of a person in white or yellow would have continued all their lives. Up to within about twenty years ago, rheas were seldom or never shot in La Plata and Patagonia, but were always hunted on horseback and caught with the bolas. The sight of a mounted man would set them off at once, while a person on foot could walk quite openly to within easy shooting distance of them; yet their fear of a horseman dates only two hundred years back--a very short time, when we consider that, before the Indian borrowed the horse from the invader, he must have systematically pursued the rhea on foot for centuries. The rhea changed its habits when the hunter changed his, and now, if an _estanciero_ puts down ostrich hunting on his estate, in a very few years the birds, although wild birds still, become as fearless and familiar as domestic animals. I have known old and ill-tempered males to become a perfect nuisance on some estancias, running after and attacking every person, whether on foot or on horseback, that ventured near them. An old instinct of a whole race could not be thus readily lost here and there on isolated estates wherever a proprietor chose to protect his birds for half a dozen years.