In Buenos Ayres these birds arrive in September, after which their shrill, angry cries are incessantly heard, while the birds are seen pursuing each other through the air or in and out amongst the trees--perpetually driven about by the contending passions of love, jealousy, and rage. As soon as their domestic broils are over, a fresh war against the whole feathered race begins, which does not cease until the business of propagation is finished. I have frequently spent hours watching the male, successively attacking, with scarcely an interval of rest, every bird, big or little, approaching the sacred tree where its nest was placed. Its indignation at the sight of a cowardly Carrion-Hawk (_Milvago_) skulking about in search of small birds' nests, and the boundless fury of its onset, were wonderful to witness. They are extremely active, and when not engaged in their endless aerial battles, are pursuing large insects on the wing, usually returning after each capture to their stand, from which they keep a jealous watch on the movements of all winged things about them. They are fond of marshy places and water-courses, where they perch on a tall stalk to watch for insects, and also frequently skim over the water like Swallows to drink and dip their feathers. A tall tree is usually selected for the nest, which is not unfrequently placed on the very topmost twigs, exposed to the sight of every creature passing overhead, and as if in defiance of birds of prey. With such an aggressive temper as this bird possesses it is not strange perhaps that it builds in the most exposed places, from which the female, in the absence of her vigilant consort, can keep a sharp eye on the movements of her feathered neighbours; but I have often thought it singular that they do not make a deeper receptacle for their eggs, for the nest is merely a slight platform of slender sticks, and very ill-adapted to retain its burden during high winds. The parasitical Cow-bird never enters this nest, which is not strange. The eggs are four in number, small for the bird, pointed, parchment-white, spotted with dark brown at the larger end. 171. MILVULUS TYRANNUS (Linn.). (SCISSOR-TAIL TYRANT.) +Milvulus tyrannus+, _Scl. et Salv. Nomencl._ p. 53; _Durnford, Ibis_, 1877, p. 178 (Buenos Ayres); _Gibson, Ibis_, 1880, p. 26 (Buenos Ayres); _Barrows, Bull. Nutt. Orn. Cl._ vol. viii. p. 203 (Entrerios). +Tyrannus violentus+, _Burm. La-Plata Reise_, ii. p. 453. _Description._--Above cinereous, rump blackish; cap jet-black, with a concealed yellow vertical crest; wings dark brown; tail black, outer web of the outer rectrix white; beneath white; bill and feet black; three outer primaries excised at the tips: whole length 14·0 inches, wing 4·6, tail 12·0. _Female_ similar, but outer tail-feathers not so long. _Hab._ Mexico, and Central and South America, down to Patagonia.