174 Birds of Colorado 
bt 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 borealis 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; Gilman 07, p. 154; Warren 08, 
p. 20; 09, p. 14; Rockwell 08, p. 162. 
Description.—Adult female—Above dark smoky-brown throughout, 
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 little 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. 
Tho Western Red-tail is the commonest of the larger Hawks in 
Colorado ; it is a resident, though much more common in the summer. 
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, 
