193 
son’s Hawk by slightly rounder, less-pointed wing tips, and by the breast being lighter 
instead of darker than the abdomen. From the two Rough-legged Hawks, the Red-tailed 
is separated with greater ease as a rule. It is never as evenly dull ochre on the breast, 
nor has it the decided, sharply defined black abdominal band of the characteristic American 
Rough-legged (Figure 217). It is rarely as solidly white below, nor are the pantaloons in 
so deep rufous contrast as is usual in the Ferruginous. The tail, except in the Krideri 
phase (See following), is not as white, and even in that form it never whitens towards the 
base, nor are there white spots on either side of the rump. Another point of distinction 
is that although the inner webs of the primaries lighten towards their bases, they do not 
separate in any normal flight attitude to show a flash of white from above as they do in the 
Rough-leg even in the blackest phase (Figure 220). 
Nesting. In bulky nests in tree tops. 
Distribution. Across the continent as far north as the tree limit. More common in 
breeding season in the wooded than in the prairie sections, but common throughout the 
latter in migration. 
SUBSPECIES. The Red-tailed Hawk has been divided into several races. The 
Eastern Red-tail Buteo borealis borealis extends westward through Ontario; but, beginning 
with the prairie sections in Manitoba, it intergrades, intermixes, and interbreeds so thorough- 
ly with the Western Red-tail Buteo borealis calurus that there is great difficulty in defining 
the distinctive characters or saying where one begins and the other leaves off. Almost 
typical eastern birds can be found westward to the mountains and the most common 
plumage of the prairie is only slightly different from that of the eastern birds. Mixed with, 
and even mated to these indeterminate birds, are those of unmistakable calurus character- 
larger amounts of black below, the dark tail of the juvenile more or less mixed with red, 
and the red tail of the adult more or less barred with dark. Strangely, the particular type 
of coloration upon which the name B.b. calurus is founded, a black-phased bird with a 
black-barred red tail, although common farther south, has not as yet been detected in 
Canada. In British Columbia a redder type occurs. It is a heavily coloured plumage, 
with a reddish tendency across the breast. This coloration is not often seen on our prairies. 
Besides these two forms, borealis and calurus, there are two others recognized by the 
Check-list that present peculiar problems to the Canadian ornithologist — Krider's Hawk 
Buteo borealis krideri and Harlan’s Hawk Buteo borealis harlani. These are so variable 
that it is difficult to say just what are their distinguishing characters or whether after all 
they are not respectively just the light and dark extremes of the Western Red-tad. 
Krider’s Hawk Buteo borealis krideri is like a whitened Buteo borealis with much white 
on head, tail, and intermixed on the back. The tail of the adult may be pale red, cream 
colour, or even pure white, and may be sharply barred or nearly immaculate. This form 
is not common anywhere, but is most numerous from Iowa to Manitoba and occurs 
irregularly west to the mountains. Birds of krideri appearance occur sporadically through- 
out the west, north even to the Yukon. 
Harlan’s Hawk Buteo borealis harlani on the contrary was originally based on a black 
Red-tail that had a considerable admixture of grey mottling and a black tail with a 
slight yellow tip. Whether these are essential characters of a distinct subspecies or only 
individual colour variations to a highly variable single race is not clear, but harlani ten- 
dencies occur in some specimens of otherwise pure calurus type. Birds with dark tails 
mottled or marbled with greyish or reddish, are usually referred to this race, but some 
authorities refer any dark-phased Red-tail with black tad to harlani , and there is lack of 
unanimity as to the essential characters of the race. 
Owing to the uncertainty of the subspecific characters, lack of definite geographic 
range, and to regular interbreeding with calurus or borealis the writer is inclined to discard 
both krideri and harlani as separable subspecies and to regard them as the light and dark 
extremes of calurus whose most distinctive character from borealis is great variability. 
Another rather slightly characterized subspecies, the Alaska Red-tailed Buteo borealis 
alascensis, has been described from southeastern Alaska and may occur in British Columbia. 
It is a small calurus , but with dark areas a blacker brown. It is not known whether it is 
double phased. 
81054—13 
