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 
edged 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-lines 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; culmen 1-6; tarsus 3-6. A 
male is much smaller—wing 16-5. 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 «» few brown spots and streaks here 
and there. 
Dark or melanistic phase—sooty-black above and below, except 
for the under side of the tail-feathers and the bases of the wing- 
quills 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 least as far north as Colorado. 
The Ferruginous Rough-leg, perhaps more commonly known as the 
Squirrel-Hawk, is « fairly common resident-bird in eastern Colorado 
on the plains and up into the parks, breeding soth in the plains and as 
high as Breckenridge (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 Butte. 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), E] 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 
