Volume Ii Part 13 (1/2)

[Plate XVI.]

[Ill.u.s.tration: BUTEO SWAINSONI.]

+Buteo swainsoni+, _Scl. et Salv. Nomencl._ p. 118; _Withington, Ibis_, 1888, p. 469 (Lomas de Zamora); _Baird, Brew., et Ridgw.

N. A. B._ iii. p. 263. +Buteo obsoletus+, _Sharpe, Cat. B._ i. p.

184. +Buteo albicaudatus+, _Scl. et Salv. P. Z. S._ 1869, p. 634 (Buenos Ayres).

_Description._--Above blackish brown; scapulars slightly variegated with rufous; upper tail-coverts white, tinged with rufous; tail dark greyish brown, crossed by several ill-defined blackish bars: beneath white or pale ochraceous; a broad band covering the whole breast reddish brown; bill black; feet yellow; claws black: whole length 200 inches, wing 150, tail 85. _Female_ similar, but larger.

_Hab._ North and South America.

The figure given herewith (Plate XVI.) represents a fine adult female specimen of this Buzzard, obtained by Mr. Frank Withington at Lomas de Zamora, on the 4th of February, 1886, and now in Sclater's collection.

Swainson's Buzzard is a North-American species, which has only recently been ascertained to occur in the southern part of the Western Hemisphere. Full details concerning it are given in the standard work on ”North-American Land-birds,” to which we have referred above. Messrs.

Baird, Brewer, and Ridgway divide the species into two subspecies, ”_swainsoni_” and ”_oxypterus_” to the latter of which they refer the southern specimens, but they acknowledge that it is ”difficult to express points of absolute difference” between these subspecies.

It appears from what these authorities say (_l. c._ p. 268) that a young specimen procured by Hudson at Conchitas in 1860, and referred by Messrs. Salvin and Sclater with doubt to _B. albicaudatus_, really belongs to _B. swainsoni_. A second undoubtedly Argentine example is that procured by Mr. Withington and now figured.

Like other Buzzards, _B. swainsoni_ varies much in plumage, and occasionally a.s.sumes a melanistic form, under which it was described and figured by Sclater in 1858 as _Buteo fuliginosus_ (_cf._ P. Z. S. 1858, p. 356, and Trans. Zool. Soc. vol. iv. p. 267, pl. lxii.). Mr. Gurney is of opinion that d'Orbigny's _Buteo unicolor_ is also referable to this form of _B. swainsoni_ (_cf._ Ibis, 1889, p. 134).

A well-known writer on North-American birds (Capt. C. E. Bendire) gives the following account of the nesting of _Buteo swainsoni_ in Arizona:--

”This species is by far the commonest Hawk in the vicinity of Fort Huachuca, and a resident throughout the year. Lieutenant Benson found not less than forty-one of their nests containing eggs between May 14 and June 18, 1887. These were all placed in low mesquite trees and bushes, from 3 to 15 feet from the ground. Only six of these nests contained three eggs each, twenty-one nests contained two eggs, the remaining fourteen but a single egg. Many of the latter were undoubtedly laid by birds that had been robbed before, especially where the same nest was used again, which was frequently the case, and a few were uncompleted sets. Two eggs is the usual number laid by these birds, in Arizona at least. The nests were bulky platforms, composed of sticks of various sizes, with but a slight depression in the centre, and sparingly lined with a few bunches of dried gra.s.s. Lieutenant Benson writes me that after the Arkansas King-birds (_Tyrannus verticalis_, Say) began to build he invariably found one of their nests in any tree that contained a Swainson's Hawk's nest. In one case, a pair of these birds had placed their nest directly under, and but 8 or 9 inches from that of the Hawk.

A pair of White-rumped Shrikes (_Lanius ludovicianns excubitoroides_) built also immediately below one of these Hawk's nests.

”When not closely looked at, many of the eggs of Swainson's Hawk appear to be unspotted, but on careful examination there are in reality but very few that are immaculate. Out of a series of sixty-nine specimens sent by Lieutenant Benson there are but three unspotted ones. The ground-colour of these eggs when fresh is a very distinct greenish white, which in course of time fades into a dull yellowish white, even if the eggs are not exposed to light. They are more or less heavily spotted and blotched, varying in colour from burnt-umber to tawny olive, and in some of the lighter coloured specimens from a French grey to a drab-grey. Their shape ranges from a short ovate to an oval, and they average about 223 by 171 inches in length and width.”

296. BUTEO ALBICAUDATUS (Vieill.).

(WHITE-TAILED BUZZARD.)

+Buteo albicaudatus+, _Durnford, Ibis_, 1877, p. 187 (Buenos Ayres); _Doring, 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 (Gualeguaychu); _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 210 inches, wing 180, tail 80. _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 n.o.bler 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 pa.s.sing the day scattered about the adjacent plain, feeding on gra.s.shoppers 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.

297. BUTEO ERYTHRONOTUS (King).

(RED-BACKED BUZZARD.)

+Buteo erythronotus+, _Sharpe, Cat. B._ i. p. 172; _Scl. et Salv.

Nomencl._ p. 119; _Scl. P. Z. S._ 1872, p. 536 (Rio Negro); _Durnford, Ibis_, 1877, p. 38, et 1878, p. 397 (Patagonia); _Salvin, Ibis_, 1880, p. 362 (Salta); _Barrows, Auk_, 1884, p.