This is a fine bird--the king of South-American Buzzards. In the adult female the three colours of the plumage are strongly contrasted; the back being rusty rufous, the rest of the upper parts grey, the whole under surface pure white. It is occasionally met with in the northern provinces of the Argentine Republic, but is most common in Patagonia; and it has been said that in that region it takes the place of the nearly allied _Buteo albicaudatus_ of Brazil. In habits, however, the two species are as different as it is possible for two raptores to be; for while the northern bird has a cowardly spirit, is, to some extent, gregarious, and feeds largely on insects, the Patagonian species has the preying habits of the Eagle, and lives exclusively, I believe, or nearly so, on cavies and other small mammals. When Captain King first discovered it in 1827, he described it as "a small beautiful Eagle." In Patagonia it is very abundant, and usually seen perched on the summit of a bush, its broad snowy-white bosom conspicuous to the eye at a great distance--one of the most familiar features in the monotonous landscape of that grey country. The English colonists on the Chupat, Durnford says, call it the "white horse," owing to its conspicuous white colour often deceiving them when they are out searching for strayed horses in the hills. It is a wary bird, and when approached has the habit of rising up in widening circles to a vast height in the air. When sailing about in quest of prey it usually maintains a height of fifty or sixty yards above the surface. The stomachs of all the individuals I have examined contained nothing but the remains of cavies (_Cavia australis_). The nest is built on the top of a thorn bush, and is a large structure of sticks, lined with grass, fur, dry dung, and other materials. "The eggs are greyish white in colour, blotched and marked, principally towards the large end, with two shades of umber-brown" (_Gould_). 298. ANTENOR UNICINCTUS (Temm.). (ONE-BANDED BUZZARD.) +Asturina unicincta+, _Burm. La-Plata Reise_, ii. p. 436 (Mendoza). +Urubitinga unicincta+, _Scl. et Salv. Nomencl._ p. 119; _Gibson, Ibis_, 1879, p. 411 (Buenos Ayres); _Salvin, Ibis_, 1880, p. 362 (Salta); _Withington, Ibis_, 1888, p. 469 (Lomas de Zamora). +Antenor unicinctus+, _Ridgw. N. A. B._ iii. p. 249 (1874). +Erythrocnema unicincta+, _Sharpe, Cat. B._ i. p. 85. _Description._--Above black, upper wing-coverts chestnut; upper tail-coverts white; tail black, concealed base and tip white: beneath black; thighs deep ferruginous; crissum white: whole length 23·0 inches, wing 14·5, tail 9·5. _Female_ similar, but larger. _Hab._ North and South America.