Smaller than the preceding. Adult. Wing-coverts, from its flexure to the body, fine bright rufous; breast and other inferior parts paler rufous; many feathers with narrow lines of black on their shafts, and spotted and barred transversely with white; the latter color predominating on the under tail-coverts. Entire upper-parts brown; on the head and neck much mixed with rufous, and with white spots on the wing-coverts and shorter quills and rump; quills brownish-black, spotted with white on their outer webs, and with bars of a lighter shade of the same color and of white on their inner webs; tail brownish-black, with about five transverse bands of white, and tipped with white. Younger. Under parts with large sagittate spots and wide bars of rufous, tinged with brown. Young. Entire under-parts yellowish-white, with longitudinal stripes and oblong spots of brown; throat brown; upper parts brown, with partially concealed spots and bars of white; quills dark-brown, with wide bars of rufous, and white on both webs; tail brown, with many bands of pale brownish and rufous-white; tail beneath silvery-white. Dimensions. _Female_—total length, 22 to 24 inches; wing, 14; tail, 9 inches. _Male_—total length, 18 to 20 inches; wing, 11½ to 12; tail, 8 inches. Hab. North America; Oregon (Townsend); California (Heermann); Wisconsin (Hoy); South Carolina (Gibbes). Obs. An abundant and rather difficult species to the student. The young bird, which is _Falco hyemalis_ Gm., is the more usually met with, and bears very little resemblance to the adult. 4. Buteo Bairdii. Hoy, Proc. Acad. Philada., VI. p. 451. (1853.) Female. Rather smaller than _B. lineatus_; wings long and pointed; third primary longest; tail moderate, rounded. Entire upper-parts dark brown, with a purplish-bronze lustre, especially on the primaries; plumage of the head and neck behind, and some feathers on the back, edged and tipped with yellowish-white; upper tail-coverts yellowish-white, with transverse bars of brown. Tail above brownish-cinereous, and having about ten narrow bands of brownish-black, and tipped with white. Under parts pale yellowish-white, or fawn color, with a few sagittate spots of brown on the sides, and a stripe of brown running downwards from the corner of the mouth. Forehead white; under wing-coverts yellowish-white. Cere, legs, and irides, yellow.