Young female (33,508, San José, Costa Rica; J. Carmiol). Differs from the type chiefly in lighter colors. The whole forehead very broadly immaculate dull white, this continuing back to the occiput in a broad unstreaked superciliary stripe; along the upper edge of the ear-coverts is a rusty suffusion, with condensed, fine dusky streaks, forming an indistinct stripe separating the wholly white ear-coverts from the supraoral stripe; the “mustache” is very conspicuous; the breast has a few large tear-shaped spots of clear blackish-brown, and the sides have very sparse, irregular, and more sagittate spots of the same; the whole posterior parts are immaculate. The upper parts are more variegated with paler, the wing-coverts and rump having the feathers irregularly bordered with whitish. The upper tail-coverts are white, barred with dark brown. Tail, hoary brown, crossed by nine or ten nearly obsolete, narrow bands of dusky. Whole lining of the wings immaculate, except the conspicuous patch on the primary coverts. The whole under surface of the primaries is uniform slaty, gradually deepening into black towards ends. Wing-formula, 3–4–2–5–6–7, 1. Wing, 15.00; tail, 8.00; tarsus, 2.45; middle toe, 1.55. Primaries project beyond secondaries, 6.00.
Hab. Tropical America, from the southern border of the United States to Buenos Ayres.
The melanistic specimen described above agrees perfectly with Mr. Sclater’s excellent figure of his B. fuliginosus above cited, and the only discrepancy in the description is in the measurements,—those given for the B. fuliginosus being, wing 12.00, tail 6.50, and tarsus 2.60. This difference—certainly not great—very likely indicates the proportions of the sexes, while the discrepancy as regards the length of the tarsus, it is probable, results from a different mode of measurement.
The present form is very nearly related to the true B. swainsoni, and, though distinguishable, we find it difficult to express points of absolute difference. The essential distinctions, however, are the longer primaries and lighter colors of the present bird, there being in the immature plumage of oxypterus no approach to the deep, fine ochraceous, the characteristic and prevalent tint of the young B. swainsoni. The spots beneath are more sparse, and there does not appear to be that tendency to their aggregation on the sides of the breast as generally seen in swainsoni.
Both agree, however,—and differ from all other species,—in the unbarred slate-color of the under surface of primaries, the plain black of the outer surface, conspicuous “mustache,” obscurely barred gray tail, etc. In fact, the general pattern is almost exactly the same, while there is little difference in relative proportions.
In view of the very appreciable, though rather indefinite, differences above indicated, and the obscure history of the present bird, we prefer, at least until more familiar with its different stages, to recognize it under the above name.
A third specimen, from Buenos Ayres (Conchitas; William H. Hudson),—exactly similar, in all particulars, to the two specimens described,—was labelled by Mr. Sclater, B. albicaudatus, Vieill., which is usually placed as a synonyme under B. pterocles, an exclusively South American species; though belonging strictly to the same section of the genus with the present bird and B. swainsoni, it is quite distinct, the Smithsonian Collection containing numerous examples illustrating the several stages of plumage.
Habits. Taking the two varieties together, this species appears to range over the entire continent of America, from the Arctic regions to the cold-temperate portion of South America. In Arctic America it appears to have a western distribution, though extending far to the north during the breeding-season, and being more or less nomadic during the winter. A single well-marked specimen was taken by Mr. Brewster, in the winter of 1871–72, in the eastern part of Massachusetts. It was first noticed by Dr. Richardson, and was by him supposed to be identical with the common Buzzard of Europe. It was met with in the fur country, where it was migratory, arriving there early in April, and departing again about the end of September. It frequented the low alluvial points of land which stretch out under the high banks of rivers, where it might be observed sitting for a long while motionless on the bough of a tree, waiting patiently for some small birds or quadrupeds to pass within its reach. As soon as it perceived anything of the kind, it would glide silently into the air and sweep easily but rapidly down upon its prey. One of Dr. Richardson’s specimens was found to have two whole toads in its stomach.
Dr. Richardson states that this Buzzard builds its nest on a tree, of short sticks, lining it sparingly with deer’s hair. The eggs, from three to five in number, are described as equalling in size those of the domestic fowl, and as having a greenish-white color, with a few large dark brown blotches at the larger end. It was seen by the doctor as far to the north as the 57th parallel.