Icterus bullocki.
In view of the difficulties attendant upon the definition of subordinate groups among the United States Icterinæ, we propose to consider them all under the single genus Icterus, leaving it for some one with more ingenuity to establish satisfactory divisions into sub-genera.[34]
The colors of the Orioles are chiefly black and yellow, or orange, the wing sometimes marked with white. The females are generally much duller in plumage, and the young male usually remains in immature dress till the third year. In all the North American species the rump is of the same color with the belly; the chin, throat, and tail, black.
In the North American Orioles the baltimore and bullocki have the tail but little graduated; spurius, more so; the others very decidedly graduated. The bills of the two first mentioned are stout and nearly straight; that of I. melanocephalus quite similar. I. parisorum has the bill more attenuated, but scarcely more decurved; in spurius it is attenuated and decurved, much as in wagleri; this character is strongest in I. cucullatus. The much graduated tail is combined with a slender decurved bill in I. cucullatus and wagleri; with a straighter one in parisorum; with a thick, nearly straight, one in melanocephalus. The arrangement, according to the graduation of the tail, would be baltimore, bullocki, spurius, parisorum, wagleri, melanocephalus, and cucullatus. According to stoutness and curvature of bill, it would be baltimore, melanocephalus, bullocki,parisorum, spurius wagleri, and cucullatus.
All the species have the rump and under parts yellow or orange. All have the head entirely black, except bullocki, in which its sides are orange, and cucullatus, which has an orange crown. All have black on the throat. In the species with black head and neck, all have the tails black towards the end, except bullocki and baltimore.
The females and young males are so entirely different in colors from the adult males, and so similar in the different species, that they can best be distinguished by the details of form and size. The I. prosthemelas and I. melanocephalus are placed, according to the above arrangement, in different subgenera, yet the young male of the former and the adult male of the latter are so perfectly similar in colors as to be undistinguishable in this respect, and require careful examination of points of external structure to be separated (see description of I. melanocephalus, p. 782).
The following synopsis may help to distinguish the North American Orioles and their nearest allies, as far as color is concerned.
Species and Varieties.
ICTERUS. Head all round deep black, sharply defined against the yellow of the nape; wings black, with or without white markings. Body generally, including lesser wing-coverts, deep greenish-yellow (intense orange-red in some South American species).