While watching their antics, which the Gauchos call the Téru's quadrilles, a curious subject of inquiry suggested itself to my mind. It appeared to me that its manner of playing has had a reflex effect strong enough to mark the bird's whole character--language, bearing, and habits being coloured by it, and even the domestic relations interfered with. And with regard to the latter point, though it is the rule that each cock bird has only one hen, I have known several instances of a cock with two hens, the two females laying their eggs in one nest and taking turns in sitting on them. I have also found instances of two males to one female; and in one case, where I watched the birds, I noticed that when the female was on the nest the males stood over her, one on each side. I once had my attention drawn to a large concourse of Térus by the strange behaviour of two individuals amongst them, and I stayed to watch their proceedings. It was in the dry hot weather, and a great many birds had congregated to drink at a lagoon. Some hundreds of them were standing about, quietly preening their feathers, and in the middle of the flock two birds were conspicuously marching about, stiff and upright as a couple of soldiers engaged in some military exercise, and uttering loud notes full of authority. Every few minutes a fresh bird would arrive and alight at some distance from the water, on which the two noisy birds would bustle up, and, ranging themselves behind it, run it with loud drumming notes to the margin; then, standing close together, they would wait till its thirst was quenched, after which they would run it away to some distance from the water, of which they seemed to have made themselves dispensers. For over an hour I continued watching them, and every bird that arrived was conducted to and from the water in this ceremonious manner. Occasionally several couples unite and soar about in a compact flock; they divide into sets of three birds each, then hover for some time, all waving their wings exactly in time and screaming their notes in unison, and these movements seem like an imitation in the air of the usual marching and drumming performance on the ground. The breeding-season of the Térus begins as early as the month of June in favourable seasons; severe cold, drought, or other causes sometimes delays it to August. The nest is a shallow circular hollow made by the bird on the level plain, and lined with broken grass-stems and small fragments of thistle-stalks; the eggs are four, rather sharply pointed at one end, and have an olive-green ground-colour spotted with black. The eggs in different nests vary greatly in size, ground-colour, and in the amount of black they are marked with, no two birds laying eggs exactly alike.