(WHITE-TAILED BUZZARD.)
+Buteo albicaudatus+, _Durnford, Ibis_, 1877, p. 187 (Buenos Ayres);
_Döring, Exp. al Rio Negro_, p. 51 (Rio Negro); _Withington,
Ibis_, 1888, p. 469 (Lomas de Zamora). +Tachytriorchis
albicaudatus+, _Sharpe, Cat. B._ i. p. 162. +Buteo pterocles+,
_Scl. et Salv. Nomencl._ p. 119; _Barrows, Auk_, 1884, p. 109
(Gualeguaychú); _White, P. Z. S._ 1882, p. 622 (Buenos Ayres).
_Description._--Above greyish black, scapulars and upper
wing-coverts ferruginous; 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.
_Hab._ 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 sometimes 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 coleopterous 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.