When persecuted, Rheas soon acquire a wary habit, and escape by running almost before the enemy has caught a sight of them; or else crouch down to conceal themselves in the long grass; and it then becomes difficult to find them, as they lie close, and will not rise until almost trodden on. Their speed and endurance are so great that, with a fair start, it is almost impossible for the hunter to overtake them, however well mounted. When running, the wings hang down like those of a wounded bird, but usually one wing is raised and held up like a great sail, for what reason it is impossible to say. When hard pressed, the Rhea doubles frequently and rapidly at right angles to its course; and if the pursuer's horse is not well trained to follow the bird in all its sudden turns without losing ground he is quickly left far behind. In the month of July the love-season begins, and it is then that the curious ventriloquial bellowing, booming, and wind-like sounds are emitted by the male. The young males in the flock are attacked and driven off by the old cock-bird; and when there are two old males they fight for the hens. Their battles are conducted in a rather curious manner, the combatants twisting their long necks together like a couple of serpents, and then viciously biting at each other's heads with their beaks; meanwhile, they turn round and round in a circle, pounding the earth with their feet, so that where the soil is wet or soft they make a circular trench where they tread. The females of a flock all lay together in a natural depression in the ground, with nothing to shelter it from sight, each hen laying a dozen or more eggs. It is common to find from thirty to sixty eggs in a nest, but sometimes a larger number, and I have heard of a nest being found containing one hundred and twenty eggs. If the females are many the cock usually becomes broody before they finish laying, and he then drives them with great fury away and begins to incubate. The hens then drop their eggs about on the plains; and from the large number of wasted eggs found it seems probable that more are dropped out of than in the nest. The egg when fresh is of a fine golden yellow, but this colour grows paler from day to day, and finally fades to a parchment-white. After hatching, the young are assiduously tended and watched over by the cock, and it is then dangerous to approach the Rhea on horseback, as the bird with neck stretched out horizontally and outspread wings charges suddenly, making so huge and grotesque a figure that the tamest horse becomes ungovernable with terror. Eagles and the large Polyborus are the enemies the Rhea most fears when the young are still small, and at the sight of one flying overhead he crouches down and utters a loud snorting cry, whereupon the scattered young birds run in the greatest terror to shelter themselves under his wings. 434. RHEA DARWINI, Gould. (DARWIN'S RHEA.)