174 Birds of Colorado 



b"- Above lighter, with a good deal of white, especially on the 

 head and tail-coverts ; tail pale rufous. 



B. b. krideri, p. 175. 

 b. Outer webs of primaries spotted with white. B. 1. elegans. 

 B. Only the three outer primaries emarginate on the inner web. 



B. swainsoni, p. 176. 



Western Red-tail. Buteo horealis calurus. 



A.O.U. Checklist no 337b — Colorado Records — Baird 54 p. 12 

 {B. montanus) ; Allen 72, p. 152 ; Drew 81, p. 141 ; 85, p. 17 ; Dille 

 87, p. 97 ; Morrison 88, p. 115 ; 89, p. 7 ; Kellogg 90, p. 87 ; Lowe 

 94, p. 267 ; McGregor 97, p. 38 ; Cooke 97, pp. 75, 204 ; Dille 03, p. 74 ; 

 Henderson 03, p. 235 ; 09, p. 229 ; Oilman 07, p. 154 ; Warren 08, 

 p. 20 ; 09, p. 14 ; Rockwell 08, p. 162. 



Description. — Adult female — Above dark smoky-brown tliroughout, 

 with a few inconspicuous traces of tawny to the edges of some of the 

 feathers, but hardly a trace of white ; tail rich rufous, with a sub- 

 terminal band of black and traces of other bands more or less complete, 

 and a narrow whitish tip ; below mingled smoky-brown and tawny, 

 the former chiefly on the throat and belly, the latter chiefly on the 

 breast and thighs ; iris brown, bill bluish-horn, cere yellowish, legs 

 yellow. Length 22-5 ; wing 16 ; tail 8-5 ; culmen 1-4 ; tarsus 3-6. 



The male is smaller — wing 15.25. Other individuals in the light 

 phase are rather paler above, and are more marked with tawny, while 

 below they are chiefly white with a httle tawny on the throat and a 

 few dark shaft-marks across the belly. In this plumage they are hardly 

 separable from the true B. borealis. Intergrades between the dark 

 and light phases are quite common. 



Young birds are like the adults, but have a little more white and 

 tawny ; the tail like the back with 10 — 12, narrow, dusky black, trans- 

 verse bars and a terminal white tip ; below white with a few spots of 

 smoky brown, and the thigh transversely banded or showing traces of 

 transverse bands of dusky tawny. 



Distribution. — Western North America from Mackenzie and British 

 Columbia south along the eastern bases of the Rocky Mountains to 

 north-west Texas and west to the Pacific. 



The Western Red-tail is the commonest of the larger Hawks in 

 Colorado ; it is a resident, though much more common in the su:nmer. 

 The migrants arrive in March and breed in May and early June from the 

 plains up to at least 12,000 feet, according to Drew, though I know of 

 no definite record higher than Breckenridge (9,500 feet). 



The following are recorded localities : Willow Creek, Weld co., breed- 

 ing (Dille 87) ; Estes Park (Kellogg) ; Boulder co., wintering in valley. 



