180 Birds of Colorado 



Markman 07, p. 156 ; Richards 08, p. 38 ; Henderson 09, p. 229 ; 

 Warren 10, p. 30. 



Description. — Normal phase — Above dusky-brown, the feathers 

 fedged with tawny-rufous and a little white, more pronounced toward 

 the neck and head ; tail white at the base and tip, rest ashy tinged 

 at the edge with tawny ; below white, legs and thighs rich chestnut 

 barred with dusky, a few cross-Unes of dusky on the belly and shaft- 

 lines on the breast ; iris yellow to brown, bill bluish-horn, greenish- 

 yellow at the base, below and on the cere ; legs yellow. Length (of a 

 female), 24-5 ; wing 18-5 ; tail 9'75 ; cuhnen 1-6 ; tarsus 3-6. A 

 male is much smaller — wing lO-S. A young bird has less tawny and 

 more white above, and traces of dusky bands on the tail ; below pure 

 white including the legs, with a few brown spots and streaks here 

 and there. 



Dark or raelanistic phase — sooty-black above and below, except 

 for the under side of the tail-feathers and the bases of the wing- 

 quiUs above the notch on the inner web, where it is white ; inter- 

 mediate forms varied with tawny to a greater or less extent are 

 frequently met with. 



Distribution. — Western North America from Saskatchewan to Mexico, 

 and from the Dakotas and Texas to the Pacific ; chiefly on the plains 

 and prairies. A resident at laast as far north as Colorado. 



The Ferruginous Rough-leg, perhaps more commonly known as the 

 Squirrel-Hawk, is a fairly common resident-bird in eastern Colorado 

 on the plains and up into the parks, breeding 'joth in the plains and as 

 high as Breckenridgo (Carter), but wintering chiefly in the plains. It 

 does not seem to be common on the western slope, though Warren 

 tells me he saw it in the fall near Crested Butto. Rockwell gives no 

 definite information of its occurrence in Mesa co. The following are 

 recorded localities : Estes Park, common (Kellogg), near Boulder 

 (Henderson), Weld co., breeding (Dille), Littleton, near Denver, on • 

 Christmas Day (Richards), El Paso co., January and June (Aiken coll.), 

 Limon, breeding (Aiken), near Medano Ranch, July (Warren). 



Habits. — This large and powerful Hawk is chiefly 

 a bird of the open plains and prairies, where it gets its 

 living by preying on ground-squirrels or gophers, other 

 small mammals and reptiles ; it never seems to kill 

 birds or poultry — perhaps its flight is too sluggish. It 

 builds a very large nest in the branches of a cotton-wood 

 or willow in Colorado, but in localities where trees are 

 scarce it nests on the ground, usually on rocky hillsides 



