Middle age or winter plumage? Entire upper plumage, brownish black, slightly mixed with rufous on the head and neck behind, white of the face, and under parts more deeply tinged with reddish yellow, dark stripes wider, plumage of the sides, with wide transverse bands of brownish black, predominating on some feathers, and the yellowish white, assuming the form of circular spots. Tail dark brown, nearly black tipped, and with four bars of white, upper tail coverts with spots of white at their bases. Feet yellow. Younger and adult female? Entire upper plumage, dusky brown, quite light, and with a tinge of ashy in some specimens. Head above with narrow stripes of dark brown and rusty red, and in some specimens, many irregular spots and edgings of the latter color, on the other upper parts. Forehead and entire under parts white, with longitudinal stripes of light brown. Plumage of the sides and flanks light brown, with pairs of circular spots of white, tibia white, with dashes of brown, tail above and below pale brown, with about six bands of white. Neck behind with a distinct band of white. Dimensions. Total length (of skin,) females, 12 to 14 inches, wing, 8 to 9, tail, 5½ inches. Male. Total length, 10 to 11 inches, wing, 7½ to 8, tail, 5 inches. Hab. North and South America. Wisconsin, (Dr. Hoy.) California, (Mr. J. G. Bell.) Oregon, (Col. M’Call, Dr. Townsend.) Cuba, (M. de Sagra.) Jamaica, (Mr. Gosse.) New Granada, (M. Parzudaki.) Bermuda, (Sir. W. Jardine.) Spec. in Mus. Acad. Philada. Obs. The adult of this species is with difficulty distinguishable from the European _H. æsalon_, but we have never seen the latter in the nearly black plumage, which we regard as characterizing the young or winter plumage, of the American bird. The light, “liver brown” plumage, represented by European authors as the female of _F. æsalon_, frequently occurs in this bird, and is given by Rich. and Swains. in Fauna Boreali Americana, Birds, pl. 25. The adult which appears to be _Falco temerarius_, Aud., is figured in B. of Am. pl. 75, the other figures by Aud. pl. 92, and Wilson’s plate, represent this bird in the dark plumage as described above. Adult specimens from Western America, even more closely resemble the European species, but differ from the Eastern American only in small and scarcely describable particulars, as the slightly greater extent of the white front, or the greater purity of the white of the throat and breast. We regard the stage of plumage above described as that of the female, (and as figured by Rich. and Swains.) principally on account of its analogy to the female of the nearly allied European species. This bird is of frequent occurrence in the United States. The largest specimens that we have ever seen are from Oregon, and may prove to be of a distinct species, though we cannot at present, determine. IV. GENUS TINNUNCULUS. Vieill. Ois. d’Am. Sept. I. p. 39. (1807.)