BUTEO ALBICAUDATUS. 61 



296. BUTEO ALBICAUDATUS (Vieill.). 

 (WHITE-TAILED BUZZARD.) 



Buteo albicaudatus, Durnford, Ibis, 1877, p. 187 (Buenos Ayres) ; Doring, 

 E.rp. al Rio Negro, p. 51 (Rio Negro) ; Withington, Ibis, 1888, p. 469 

 (Lomas de Zaniora). Tachytriorchis albicaudatus, Sharps, Cat. B. i. 

 p. 162. Buteo pterocles, Scl. et Salv. Nomencl. p. 119 ; Harrows, Auk, 1884, 

 p. 109 (Gualeguaychii) ; White, P. Z. S. 1882, p. 622 (Buenos Ayres). 



Description. Above greyish black, scapulars and upper wing-coverts ferru- 

 ginous ; rump and tail white, the latter with a broad black subapical band, and 

 with slight narrow transverse slaty bars : beneath, throat black, abdomen white, 

 flanks more or less barred with brown ; bill black ; feet dirty yellow : whole 

 length 21 '0 inches, wing 18-0, tail 8'0. Female similar, but rather larger. 



Hob. Southern and Central America. 



This Buzzard does not breed on the pampas, where I have observed 

 it, but appears there in the spring and autumn, irregularly, when 

 migrating, and in flocks which travel in a loitering, desultory manner. 

 The flocks usually number from thirty or forty to a hundred birds, but 

 sometimes many more. I have seen flocks which must have numbered 

 from one to two thousand birds. When flying the flock is very 

 much scattered, and does not advance in a straight line, but the birds 

 move in wide circles at a great height in the air, so that a person on 

 horseback travelling at a canter can keep directly under them for two 

 or three hours. On the ground one of these large flocks will some- 

 times occupy an area of half a square league, so widely apart do the 

 birds keep. I have dissected a great many and found nothing but cole- 

 opterous insects in their stomachs; and indeed they would not be 

 able to keep in such large companies when travelling if they required 

 a nobler prey. 



At the end of one summer a flock numbering about two hundred 

 birds appeared at an estancia near my home, and though very much 

 disturbed they remained for about three months, roosting at night on 

 the plantation trees, and passing the day scattered about the adjacent 

 plain, feeding on grasshoppers and beetles. This flock left when the 

 weather turned cold ; but at another estancia a flock appeared later in 

 the season and remained all winter. The birds became so reduced in 

 flesh that after every cold rain or severe frost numbers were found 

 dead under the trees where they roosted; and in that way most of 

 them perished before the return of spring. 



