FALCONID.E — THE FALCONS. 



149 



spots, these most conspicuous on the wings and scapulars. Secondaries crossed with 

 three bands of deeper, more reddish ochraceous. Bands of the tail pure white. In other 

 respects exactly as in the male. Wing-formula, 3,2-4-1. Wing, 9.00; tail, 6.10; 

 culrnen, .55; tarsus, 1.40; middle toe, 1.51. 



Youmj male (40,516, Fort Rice, Dacotah, July 20, 1865 ; Brig.-Gen. Alfred Sully, U. S. A., 

 S. M. Rothamnier). Differing from the adult only in minute details. Upper surface with the 

 rusty borders of the feathers nioie 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 tlie adidt, and moi-e 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 tibiae, 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. ZooL, 2 ; R. Ridgway, 3. Total, 15. 



Afeasurements. 



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 col'umbarius. 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 Butco horealis and Bubo virginianus of the same country. It is doubtful 

 whether some very light-colored adult males, supposed to belong to colum- 

 Joriws, 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 

 inliabited by the present bird obtained in the breeding-season, I am still in 

 doubt whether the present form ever assumes the blue plumage. 



As regards the climatic or regional modifications experienced by the 

 Falco lithofalco on the American continent, the following summary of facts 

 expresses my present views upon the subject. First: examples identical in 

 all respects, or at least presenting no variations beyond those of an individual 

 character, may be found from very widely separated localities ; but the 

 theory of explanation is, that individuals of one race may become scattered 

 during their migrations, or wander oh" from their breeding-places. Second : 

 the Atlantic region, the region of the plains, and the region of the north- 

 west coast, have each a peculiar race, characterized by features wliich are 

 also distinctive of races of other birds of the same region, namely, very 

 dark — the dark tints intensified, and their area extended — in the north- 



