Adult male (Baranquilla, Ecuador, Crowther; Coll. G. N. Lawrence). Differing from the Florida male in being much darker; general color plumbeous-black, instead of glaucous-plumbeous; head, wings, and tail deep black. Wing-formula, 3=4, 5–2, 6–7, 1. Wing, 12.90; tail, 7.80; culmen, 1.05; tarsus, 1.65; middle toe, 1.45; hind toe, .80; its claw, 1.10.
Adult female, with traces of immature plumage (53,081, Conchitas, Buenos Ayres, September, 1867; William H. Hudson). Whole plumage (except tail-coverts) brownish-black, deepest black on head and tail; more brownish on wing-coverts and slightly glaucous on the neck. All the feathers, except those of the head, neck, and back, bordered inconspicuously with paler; these edgings more distinct and rufescent on the lesser wing-coverts; tibiæ tinged with rusty. Wing-formula, 3=4, 5–2–6–7, 1. Wing, 14.00; tail, 7.60; culmen, 1.00; tarsus, 1.70; middle toe, 1.60; hind toe, .95; its claw, 1.20.
A specimen from Mexico, supposed to be from Mirador (No. 44,444), is dark in color, like South American examples; the bill is unusually large, the chord of the culmen measuring 1.25; wing, 14.25; tail, 8.30; tarsus, 1.70; middle toe, 1.65.
Specimens examined.—National Museum, 2; Philadelphia Academy, 7; New York Museum, 2; Cab. G. N. Lawrence, 2; Museum, Cambridge, 1; Boston Society, 3. Total, 17.
[77] Rostrhamus hamatus (Vieill.). Falco hamatus, Temm. Pl. Col. 61, 231, 1899.—Illig. Mus. Berol. Buteo hamatus, Vieill. Enc. Méth. III, 1223. Rostrhamus tæniurus, Cab. J. für. Orn. 1854, p. lxxx. No. 16,634 (Amazon River; Lieutenant Herndon). Entirely uniform plumbeous, with a glaucous cast, becoming darker on the head, and black on primaries and tail; tail perfectly even, with an obscurely indicated, narrow, interrupted band of dark plumbeous across its middle portion. A specimen in the collection of the Boston Society has the bands on the tail more conspicuous, and agrees with the R. tæniurus of Cabanis. I have seen no young specimens of this species, but, judging from Temminck’s figure, cited above, they are very similar to the same stage of R. sociabilis.
[78] The females and immature males are hard to distinguish, and from the unsatisfactory character of the material at my command I have not succeeded in finding reliable characters by which these plumages of the three races may be distinguished. Consequently I give only the characters of the adult males, in defining the distinctions between them.
[79] Circus cyaneus, var. cyaneus (Linn.). Falco cyaneus, Linn. S. N. 1766, 126. Circus cyaneus, Less. Man. Orn. I, 105.—Gould, B. Europe, pl. xxxiii.—Bonap. List, 22.—Degl. Orn. Eur. I, 74.—Strickl. Orn. Syn. I, 147.—Gray, Hand List, I, 37, No. 364. Falco pygargus, Linn. S. N. 1766, 126. Circus pygargus, Steph. Zoöl. XIII, pl. ii, 41.
Specimens examined.—National Museum, 3; Philadelphia Academy, 4; New York Museum, 1; Boston Society, 5. Total, 13.
[80] Circus cyaneus, var. cinereus (Vieill.). Circus cinereus, Vieill. Nouv. Dict. H. N. IV, 1816, 454.—Darwin, Zoöl. Beag. pt. iii, 30.—D’Orb. Synop. Av. Mag. Zool. 1837.—Strickl. Orn. Syn. I, 156.—Gray, Hand List, I, 37, No. 368. Circus campestris, Vieill. Enc. Méth. III, 1823, 1213. Circus frenatus, Licht. Verz. Doubl. 1823, p. 62. Circus histrionicus, Quoy, Zoöl. Journ. III, 1826, 271.
Specimens examined.—National Museum, 7; Philadelphia Academy, 5; Boston Society, 3; Museum Cambridge, 1; Cab. G. N. Lawrence, 1. Total, 17.