“As large tracts of that country inhabited by this bird are often entirely without trees, it alights on the ground or on some slightly elevated tuft of grass or a stone, where it sits patiently for hours watching for its prey. Its food, on dissection, I found to consist almost entirely of small quadrupeds, principally various species of mice, and in one instance the crop was filled with the remains of a ground-squirrel. In plumage it appears to vary as much as its allied species, _A. sancti-johannis_. One specimen, which was shot by a soldier attached to our party, had the tail strongly tinged with the red color which characterizes that appendage in the red-tailed Hawk, (_B. borealis_). “I have several times seen a bird sailing over the prairies, about the size of the present species, but with its entire plumage deep-black and of heavy and continued flight. It was I think certainly of this genus; but never having been so fortunate as to have procured a specimen, I am unable to decide whether it was this bird, the Black Hawk (_A. sancti-johannis_), or a new species to add to this group. My impression is that it was the Black Hawk, but it may have been the present in a stage of plumage yet undescribed. “The nest and eggs of the present bird I procured on the Consumnes river, in 1851. The nest was in the forks of an oak and was composed of coarse twigs and lined with grasses; the eggs, two in number, were white, marked with faint brown dashes. This nest was placed in the centre of a large bunch of _Misletoe_, and would not have been discovered, but having occasion to climb the tree to examine some Magpie’s nests, the Hawk in flying off betrayed her retreat. The eggs of this species are quite different from those of the European _A. lagopus_, but with those of _A. sancti-johannis_, I have never had an opportunity of comparing them.” Mr. Kern’s specimens are marked as having been procured in the Tulavie valley, California, in January, 1846. He observes, in his notes in our possession, that finding this bird remarkably fat and in excellent general condition, some of the party shot it for the mess-kettle whenever opportunity offered, and found it “very good eating.” Possibly under stress of capital appetites. DESCRIPTION AND TECHNICAL OBSERVATIONS. Genus Archibuteo. Brehm. in Oken’s Isis, 1828, p. 1269. Tarsi feathered in front to the toes, but more or less naked behind. General form, compact and heavy; wings, long and broad, formed for long-continued but not very rapid flight; bill, short, curved, edges of the upper mandible festooned; tail, moderate, wide, tarsi rather long; toes, short; claws, moderately strong, curved, very sharp. Contains about six species, three of which are American. Archibuteo ferrugineus. (Lichtenstein.) Buteo ferrugineus. Licht. Trans. Berlin Academy, 1838, p. 428. Archibuteo regalis. Gray, Genera of Birds, 1 pl. 6 (1849, plate only).