Argentine Ornithology Volume Ii Part 13

[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.

109 (Azul); _Withington, Ibis_, 1888, p. 469 (Lomas de Zamora).

+Buteo tricolor+, _Burm. La-Plata Reise_, ii. p. 436 (Mendoza and Tuc.u.man).

_Description._--Above slaty blue; wing-feathers slaty, with narrow transverse bars of black; upper tail-coverts and tail white, the latter with a broad black subapical band and numerous narrow grey cross bars: beneath white, with slight grey cross bars on the belly; bill black; feet dirty yellow: whole length 25 inches, wing 185, tail 100. _Female_ similar, but back deep chestnut.

_Hab._ Southern portion of South America.

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 gra.s.s, fur, dry dung, and other materials. "The eggs are greyish white in colour, blotched and marked, princ.i.p.ally 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 230 inches, wing 145, tail 95. _Female_ similar, but larger.

_Hab._ North and South America.

This is the Common Buzzard of the Plata region. It differs from the species previously described in its greater length of wing, and in the habit of flying near the ground when in search of prey; resembling in this respect a Harrier, only its flight is slower and more loitering. It prefers an open country, but on the pampas, like all large Hawks, it meets with great persecution from the ever-vigilant, fierce-tempered Spur-winged Lapwing. I once saw one of these Buzzards, while being so persecuted, make a conquest which greatly surprised me. It was sailing over the plain, about twenty feet from the surface, harried by several Lapwings, when suddenly, just as one Lapwing swept downwards past it in the usual way, apparently missing the head of the Hawk with its sharp wing-spurs by a hair's breadth, the Buzzard struck at and seized it in its claws and bore it to the ground. The screams of the captive and its fellows quickly brought to the spot a cloud of two or three hundred Lapwings, all hovering and screaming their loudest. I ran to the spot to aid in the rescue, when seeing me coming the Buzzard rose heavily from the ground, still carrying the Plover, and flew away beyond reach.

299. HETEROSPIZIAS MERIDIONALIS (Lath.).

(BROWN BUZZARD.)

+Urubitinga meridionalis+, _Scl. et Salv. Nomencl._ p. 119; _iid. P.

Z. S._ 1869, p. 634 (Buenos Ayres); _Salvin, Ibis_, 1880, p. 362 (Salta). +Heterospizias meridionalis+, _Sharpe, Cat. B._ i.

p. 160; _Barrows, Auk_, 1884, p. 109 (Entrerios). +Asturina rutilans+, _Burm. La-Plata Reise_, ii. p. 436 (Tuc.u.man).

_Description._--Above slaty grey, pa.s.sing into ferruginous rufous on the head, and blackish on the lower tail-coverts; wing-feathers chestnut, with narrow transverse black bars and long black ends; tail black, with a broad median white band and white tip: beneath clear ferruginous red, with narrow transverse black bars; bill black, yellow at the base; feet yellowish brown: whole length 200 inches, wing 165, tail 83. _Female_ similar, but larger.

_Hab._ South America.

This Buzzard inhabits the northern portion of the Argentine Republic, and is also found in the woods and marshes along the Plata basin, ranging south to Buenos Ayres. The wings are larger and the flight slower than in the last species. The plumage is nearly of a uniform dark brown.

At Concepcion, in Entrerios, Mr. Barrows tells us it is not unfrequently seen in cold weather. In July 1880, during an almost unprecedented rise of the river, it was quite abundant. The stomach of a gorged female examined contained only young gra.s.shoppers.

300. GERANOAeTUS MELANOLEUCUS (Vieill.).

(CHILIAN EAGLE.)