GEN. CHAR. Form falcon-like; the neck short, wings long, and pointed, the primaries and rectrices strong and stiff, and the organization robust. Bill short and deep, the commissure irregularly toothed, and notched; gonys very convex, ascending terminally; cere narrow; nostril very small, nearly circular; feet small, but robust; tarsus about equal to middle toe, with a distinct frontal series of broad transverse scutellæ; claws rather short, but strongly curved, slightly grooved beneath, their edges sharp. Third quill longest; first of variable proportion with the rest. Tail moderate, the feathers wide, broader terminally, and emarginated. This genus is peculiar to America, the two most closely related genera being _Elanus_ on the one hand and _Harpagus_ on the other. Its species belong to the tropical and subtropical regions, one of them (_I. plumbea_) generally distributed throughout the intertropical portions, the other (_I. mississippiensis_) peculiar to Mexico and the southern United States. In their habits, they are very aerial, like the genus _Nauclerus_, sailing for the greater time in broad circles overhead, occasionally performing graceful evolutions as they gyrate about. Like _Nauclerus_, they are also partially gregarious, and, like it, feed chiefly on insects and small reptiles, which they eat while flying. Species. COMMON CHARACTERS. _Adult._ Uniform plumbeous, becoming lighter (whitish) on the head, and darker (blackish) on the primaries and tail. Inner webs of primaries with more or less rufous. _Young._ Beneath whitish, striped longitudinally with brownish; above much variegated: tail with several narrow whitish bands. 1. =I. mississippiensis.= _Adult._ Wings lighter than the tail, the secondaries hoary whitish; inner webs of primaries with only obscure spots of rufous, the outer webs with a very obscure stripe of the same. Tail wholly black. _Young._ Stripes beneath reddish-umber; lower tail-coverts with longitudinal shaft-streaks of the same. Second to third quills longest; first shorter than seventh and longer than sixth. Wing, 10.60–12.30; tail, 6.00–7.00; culmen, .60–.65; tarsus, 1.30–1.55; middle toe, 1.00–1.10. _Hab._ Prairies and savannas of the southern United States and Northern Mexico, from Wisconsin and Georgia to Mirador.