Falco melanopterus, Ch. Bonaparte, Synopsis of Birds of United States, p. 31.
Falco dispar, Temm. Ch. Bonaparte, Synopsis. Append, p. 435.
Adult Male. Plate CCCLII. Fig. 1.
Bill short, broader than deep at the base, with the gape very wide. Upper mandible with the cere covered at the base with bristly feathers, the dorsal line convex and declinate to the end of the cere, then curved downwards in about the third of a circle, the sides at the base sloping towards the end convex and erect, the sharp edges with a distinct festoon, the tip narrow and acute. Lower mandible with the angle very wide and long, the dorsal outline very short, ascending and slightly convex, the sharp edges inflected, the tip obliquely truncate and narrow. Nostrils elliptical, rather large, in the fore part of the cere.
Head rather large, broad, flattened above, with the superciliary ridges prominent. Eyes large, directed obliquely forwards. Neck short; body compact. Legs of moderate length; tibia long and muscular; tarsus very short, stout, roundish, covered anteriorly with feathers for half its length, the rest with small roundish scales, toes short, thick, tuberculate and papillate beneath, scaly above, like the tarsus, but with three large scutella at the end. Claws long, curved, conical, extremely pointed, that of middle toe with an inner edge.
Plumage soft, blended, full, on the back rather compact. Feathers of the cere, lore, and eyelids, bristle-pointed. Wings very long and pointed, the second quill longest, the third nearly as long, the first longer than the fourth; the first, second, and third with the outer web attenuated toward the end; the first and second with the inner web sinuated; secondaries very broad, rounded, the inner web exceeding the outer. Tail of twelve feathers, of moderate breadth, long, emarginate and rounded, the middle and lateral feathers being about equal, and eight-twelfths of an inch shorter than the second feather from the side.
Bill black; the cere and soft basal margins yellow. Iris bright red. Tarsi and toes yellow, of a darker tint than the cere; claws black. All the lower parts are pure white, with the exception of a patch on five or six of the larger wing-coverts; the forehead is also white, as are the cheeks; the superciliary bristles black, the white of the head gradually blends into the general colour of the upper parts, which is ash-grey; the smaller wing-coverts bluish-black; the shafts of the quills brownish-black; all the feathers of the tail, excepting the two middle, white; the shafts of the two middle feathers blackish-brown, of the rest white towards the end, the whole of that of the outer pure white.
Length to end of tail 16 inches, to end of claws 12 1/4, to end of wings 14 7/8; extent of wings 40; wing from flexure 13; tail 7 10/12; bill along the ridge 1 1/2/12, along the edge of lower mandible 1 5/12; tarsus 1 4/12; first toe 7/12, its claw 3/4; second toe 10 1/2/12, its claw 10/12; third toe 1/4, its claw 9 1/2/12; fourth toe 10 1/2/12, its claw 8/12. Weight 14 oz.
Adult Female. Plate CCCLII. Fig. 2.
The female is rather larger than the male, but in other respects similar.