Note 76 — Family FALCONIDÆ.—The Falcons. (continued 3)
Reading edition
Rostrhamus sociabilis, var. sociabilis (Vieill.). Herpetotheres sociabilis, Vieill. Nouv. Dict. Hist. Nat. XVIII, 318, 1818; Enc. Méth. III, 1248. Rostrhamus sociabilis, D’Orb. Voy. Am. Merid. II. 73, 1835; Synop. Av. Mag. Zoöl. 1850. Gray, List B. Brit. Mus. p. 47; Gen. and Subgen. Brit. Mus. p. 6.—Kaup, Monog. Falc. Cont. Orn. 1850, 78.—Strickl. Orn. Syn. I, 136, 1855. Falco rostrhamus, Max. Beiträg. III. 182, 1830. Cymindis leucopygus, Spix, Av. Bras. I, 7, pl. ii, 1824. Rostrhamus niger, Less. Tr. Orn. p. 56, 1831.
Hab. South and Middle America, from Buenos Ayres to Eastern Mexico (Mirador).
Localities: Guatemala (Scl. Ibis, I, 220); Ecuador (Sclater, 1860, 289); Panama (Lawrence, VII, 1861, 316); La Plata (Burmeister, II, 1861, 435); Brazil (Pelz. Orn. Bras. I, 6); Buenos Ayres (Scl. & Salv. 1869, 160).
The numerous South American specimens which have come under my notice all differ in the respects pointed out in the synopsis from West Indian and Floridan examples. The following descriptions of a pair of the southern race will show the average characters of var. sociabilis.
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.