_Young male_ (40,516, Fort Rice, Dacotah, July 20, 1865; Brig.-Gen. Alfred Sully, U. S. A., S. M. Rothammer). Differing from the adult only in minute details. Upper surface with the rusty borders of the feathers more washed over the general surface; the rusty-ochraceous forms the ground-color of the head,—paler anteriorly, where the black shaft-streaks are very conspicuous; spots on the primary coverts and primaries deep reddish-ochraceous; tail-bands broader than in the adult, and more reddish; the terminal one twice as broad as the rest (.40 of an inch), and almost cream-color in tint. Beneath pale ochraceous, this deepest on the breast and sides; markings as in the adult, but anal region and lower tail-coverts immaculate; the shaft-streaks on the tibiæ, also, scarcely discernible. Wing, 7.00; tail, 4.60. HAB. Interior regions of North America, between the Mississippi Valley and the Rocky Mountains, from Texas to the Arctic regions. LIST OF SPECIMENS EXAMINED. National Museum, 10; Museum Comp. Zoöl., 2; R. Ridgway, 3. Total, 15. _Measurements._ +----+-----------+-----------+---------+---------+-----------+----------+ |Sex.| Wing. | Tail. | Culmen. | Tarsus. |Middle Toe.|Specimens.| +----+-----------+-----------+---------+---------+-----------+----------+ | ♂ | 7.75–8.60| 5.70–6.00| .50–.60|1.42–1.55| 1.20–1.30| 8 | +----+-----------+-----------+---------+---------+-----------+----------+ | ♀ | 8.50–9.00| 6.00–6.30| .55–.58|1.55–1.65| 1.35–1.40| 7 | +----+-----------+-----------+---------+---------+-----------+----------+ Since originally describing this bird, I have seen additional examples, and still consider it as an easily recognized race, not at all difficult to distinguish from _columbarius_. Now, however, I incline strongly to the theory that it represents merely the light form of the central prairie regions, of the common species; since its characters seem to be so analogous to those of the races of _Buteo borealis_ and _Bubo virginianus_ of the same country. It is doubtful whether some very light-colored adult males, supposed to belong to _columbarius_, as restricted, should not in reality be referred to this race, as the adult plumage of the male. But having seen no adult males from the region inhabited by the present bird obtained in the breeding-season, I am still in doubt whether the present form ever assumes the blue plumage.