4. Milvago albogularis.
Plate I.
Polyborus, (Phalcobænus) albogularis, Gould, Proceedings of Zoolog. Soc. Part V. (Jan. 1837.) p. 9.
M. Fæm. fuscescenti-niger, marginibus plumarum inter scapulas fulvis; primariis secundariisque albo ad apicem notatis; gulá, pectore, corporeque subtùs albis; lateribus fusco sparsis; rostro livido, lineis nigris ornato; cerâ tarsisque flavis.
Long. tot. 20 unc. ½ rostri, 1⅝; alæ, 15¾; caudæ, 9; tarsi, 3.
Description of female specimen, believed to be applicable to both sexes.
Colour.—Head, back, upper wing coverts pitch black, passing into liver brown; feathers on back of neck and shoulders terminating in a yellowish brown tip, of which tint the external portion of the primaries, and nearly the whole of the tertiaries partake. Tail liver brown, with a terminal white band nearly one inch broad; base of the tectrices white, irregularly marked with brown: upper tail coverts white. All the feathers of the wing tipped with white, their bases irregularly barred with transverse marks of brown and white. Under surface.—Chin, throat, breast, belly, thighs, under tail-coverts, under lining of wings, and edge of shoulders perfectly white. On the flanks, however, there are some brown feathers irregularly interspersed; and on the lower part of the breast, most of the feathers show a most obscure margin of pale brown. Bill horn colour. Cere and tarsi yellow.
Birds. Pl. 1.
Milvago albogularis
Form.—Cere and nostril as in the M. Leucurus, but the bill not quite so strong. Feathers on the sides and back of head narrow and rather stiff; those on the shoulders obtusely pointed,—which character of plumage is very general in this sub-family. Wing: fourth primary very little longer than the third or the fifth, which are equal to each other. First primary three inches shorter than the fourth or longest, and more nearly equal to the sixth than to the seventh. Extremity of wing reaching to within about an inch and a half of the tail. Tarsi reticulated, with four large scales at the base: upper part covered with plumose feathers for about three quarters of an inch below the knee; but these feathers hang down and cover nearly half of the leg. Middle toe with fifteen scales, outer ones with about nine. Claws of nearly the same degree of strength, curvature and breadth as in Polyborus Brasiliensis, or in M. leucurus, but sharper than those of the latter.
| Inch. | |
| Total length | 20½ |
| Tail | 9 |
| Wings when folded | 15¾ |
| From tip of beak to anterior edge of eye | ⁹⁄₁₀ |
| Tarsus from soles of feet to knee joint | 3½ |
| Hind claw measured in straight line from tip to root | ⁸⁄₁₀ |
| Claw of middle toe, a twentieth less than that of the hind one. |
Habitat, Santa Cruz, 50° S. Patagonia. (April.)
Mr. Gould, at the time of describing this species, entertained some doubts whether it might not eventually prove to be the Phalcobænus montanus of D’Orbigny, in a state of change. I have carefully compared it with the description of the P. montanus, and certainly, with the exception of the one great difference of M. albogularis having a white breast, whilst that part in the P. montanus is black, the points of resemblance are numerous and exceedingly close. The M. albogularis, appears to be rather larger, and the proportional length of the wing feathers are slightly different; the cere and tarsi are not of so bright a colour; the middle toe has fifteen scales on it instead of having sixteen or seventeen. The black shades of the upper surface are pitchy, instead of having an obscure metallic gloss, and the feathers of the shoulders are terminated with brown, so as to form a collar, which is not represented in the figure of P. montanus, given by M. D’Orbigny. Although the main difference between the two birds, is the colour of their breasts, yet it must be observed, that in the M. albogularis there is some indication of an incipient change from white to brown in the plumage of that part. But as M. D’Orbigny, who was acquainted with the young birds of the P. montanus, (of which he has given a figure), does not mention so remarkable a modification in its plumage, as must take place on the supposition of M. albogularis being an immature bird of that species; and as the geographical range of the two is so very different, I am induced to consider them distinct. Moreover, on the plains of Santa Cruz, I saw several birds, and they appeared to me similar in their colouring. The M. albogularis is remarkable from the confined locality which it appears to frequent. A few pair were seen during the ascent of the river Santa Cruz, (Lat. 50° S.) to the Cordillera; but not one individual was observed in any other part of Patagonia. They appeared to me to resemble, in their gait and manner of flight, the P. Brasiliensis; but they were rather wilder. They lived in pairs, and generally were near the river. One day I observed a couple standing with the Carranchas and M. pezoporus, at a short distance from the carcass of a guanaco, on which the condors had commenced an attack. These peculiarities of habit are described by M. D’Orbigny in almost the same words, as occurring with the P. montanus; both birds frequent desert countries; the P. montanus, however, haunts the great mountains of Bolivia, and this species, the open plains of Patagonia.
In the valleys north of 30° in Chile, I saw several pair, either of this species, or of the P. montanus of D’Orbigny, (if, as is probable, they are different) or of some third kind. From the circumstance of its not extending (as I believe) so far south even as the valley of Coquimbo, it is extremely improbable that it should be the M. albogularis,—an inhabitant of a plain country twenty degrees further south. On the other hand, the P. montanus lives at a great elevation on the mountains of Upper Peru; and therefore it is probable that it might be found in a higher latitude, but at a less elevation. M. D’Orbigny says, “Elle aime les terrains secs et dépourvus de grands végétaux, qui lui seraient inutiles; car il nous est prouvé qu’elle ne se perche pas sur les branches.” In another part he adds, “Elle descend cependant quelquefois jusque près de la mer, sur la côte du Pérou, mais ce n’est que pour peu de temps, et peut-être afin d’y chercher momentanément une nourriture qui lui manque dans son séjour habituel; peut-être aussi la nature du sol l’y attire-t-elle; car elle y trouve les terrains arides qui lui sont propres.”[[9]] This is so entirely the character of the northern parts of Chile, that, it appears to me extremely probable, that the P. montanus, which inhabits the great mountains of Bolivia, descends, in Northern Chile, to near the shores of the Pacific; but that further south, and on the opposite side of the Cordillera, it is replaced by an allied species,—the M. albogularis of Santa Cruz.