BIRDS OF COLORADO. 
75 
337b. Buteo borealis calurus. Western Red-tail. 
Resident; abundant. Is the common Rocky Mountain 
form overlapping the range of Krider’s Hawk and breeding 
from the plains to 12,000 feet in the mountains. Is one of the 
most common hawks of the State through the summer and not a 
few spend the winter in Colorado. 
337d. Buteo borealis harlani. Harlan’s Hawk. 
Winter visitant; rare. One specimen taken by C. K- 
Aiken at Colorado Springs. (Ridgway, Auk, II. 1885, 165.) 
One was probably taken by Capt. P. M. Thorne at Fort Lyon. 
339b. Buteo lineatus elegans. Red-bellied Hawk. 
Migratory; rare. Included in the list of Colorado birds 
on the strength of the following note from Geo. F. Breninger: 
“ I saw one at Table Rock, a full plumaged bird with the breast 
to me; saw one at Fort Collins. I have handled them here 
in California and there is not the least doubt in the matter.’’ 
342. Buteo swainsoni. Swainson’s Hawk. 
Resident; common. More common on the plains than in 
the mountains. Breeds throughout the State everywhere 
below 11,000 feet. Begins building its nest the last of April, 
eggs are laid the middle of May and the young appear early in 
June. Sometimes very abundant locally. A. S. Bennetof Lay, 
Colo., says he saw a flock of flve hundred July 10, 1889. 
347a. Archibuteo lagopus sancti-johannis. American 
Rough-legged Hawk. 
Winter resident; not uncommon. Arrives from the north 
in November and remains until March. Is usually found in the 
lower parts of the mountains and on the plains. 
348. Archibuteo ferrugineous. Ferruginous Rough-leg. 
Resident; rather common. Breeds both in mountains and 
on plains, but in the winter is mostly confined to the plains 
and the lower streams below 6,000 feet. Breeds at least as far 
south as Pueblo and thence to British America. Eggs have 
been taken in Colorado as early as April 13, and well-grown 
young by May 24; but three to four weeks later than these dates 
is the more common time. 
349. Aqui la chrysaetos. Golden Eagle. 
Resident; common in favorable localities. In few, if any, 
parts of the United States is the Golden Eagle more common 
than in the more mountainous portions of Colorado. They 
breed from the foothills to at least 12,500 feet. In the winter 
they wander occasionally over the plains, but are also found in 
