Hab. Guatemala, Mexico, and adjoining parts of United States; Arizona (Coues); Santa Clara Co., Cal. (Cooper).
LIST OF SPECIMENS EXAMINED.
National Museum, 2; Philadelphia Academy, 2. Total, 4.
There can be but little doubt that this plumage denotes a younger stage of the same species as the B. zonocercus of Sclater. The adult bird described above is moulting, and two tail-feathers of the old plumage, which have not yet been cast, are precisely like those of this specimen, the new ones being entirely different, as will be seen by the description. Taking with this the exact similarity of the pattern of under side of primaries, as well as the plumage in general, and the sameness of proportions, one cannot but be convinced of their identity. The localities of the two specimens are also so near that it is scarcely possible they are distinct.
The plumage of this stage is parallel, in its relation to the adult, with that of the young of B. albifrons var. minutus, both differing from the mature stage in nearly the same particulars, the more numerous bands on the tail distinguishing the young of nearly all Buteos from adults of the same species.
An adult specimen from Mexico, in the collection of the Philadelphia Academy (without number or other indications on the label), though resembling the two specimens described, in all essential points, differs from them in regard to the coloration of the tail. The main differences are as follows: Tail deep black basally and subterminally, the tip (very narrowly) and a middle zone about 2.00 inches broad, and 1.80 from the tip, being duller and more brownish-black, this irregularly defined anteriorly, but of sharp regular definition along the posterior border; the subterminal black band is very precisely defined on the inner webs, and anterior to this nearly the whole inner web is white, irregularly blotched with black towards the base, however; the markings of somewhat longitudinal direction; the outer webs are black to the very base. Wing, 16.50; tail, 9.00; tarsus, 2.70; middle toe, 1.80. Wing-formula, 4, 3–5–2–6–7, 1.
Whether this is a progressive stage of plumage or a mere individual peculiarity, I do not feel certain, but am inclined to the latter opinion. Both this specimen and the immature one described are labelled B. albonotatus, Gray; I have been unable to refer to Gray’s original description; if there is no doubt of its being pertinent to the immature stage described, then this will be the name of the species, as it has priority; I should much regret, however, to discard the very appropriate and characteristic name zonocercus, for the other, as Mr. Sclater’s species is so satisfactorily described and accurately figured, while the original description of albonotatus is very meagre and difficult of reference.
Buteo zonocercus (adult).