126 
FALCONIFORMES 
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 194). 
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 in the A.O.XJ. Check-list has been divided 
into several races. The Eastern Red-tail (la Ruse a queue rousse de l’Est) Buteo borealis 
borealis extends westward through Ontario; but, beginning with the prairie sections in 
Manitoba, it intergrades, intermixes, and interbreeds so thoroughly with the Western 
Red-tail (la Buse a queue rousse de 1'Ouest) Buleo 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 unmistak- 
able 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. .Strange- 
ly, 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, is very rare 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-tail. 
Krider’s Hawk (la Buse de Krider) Buteo borealis krideri is like a whitened Buteo 
borealis with much white on head, tail, and intermixed on the back in variable amount and 
distribution. 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 throughout the west, north even to the 
Yukon. The present writer is not decided as to whether krideri is entitled to full sub- 
specific status or is only a light colour-variant of other Buteo borealis races. 
Harlan’s Hawk (la Buse de Harlan) Buteo borealis harlani is the name usually given 
to a phgnage form that occurs most regularly in migration in southern Manitoba and 
across the Prairie Provinces to the southern Yukon. Most characteristically it is in full 
black phase, but also occurs with a white underbody. In the adult the tail is curiously 
and variably mottled, or marbled, or clouded with shades of black, grey, and reddish, 
or any combination of these colours. The juvenile has a dark, black-barred tail and is 
not plainly, if at all, distinguishable from black-phased calurus of similar age. There is 
no unanimity among authorities as to what are the essential characters of this race or the 
systematic relation it bears to other forms of the species. This author is not certain 
whether to regard it as a distinct species that hybridized freely with Buteo borealis or 
merely a colour-variant of calurus. Its breeding range seems to centre about southern 
Yukon Territory where it interbreeds freely with calurus and krideri , but individuals with 
harlani characters are found nesting south to western Alberta. 
Economic Status. Nearly everything said of Swainson’s and the 
Rough-legged Hawks (which see) applies to this bird. Its record is not 
quite so satisfactory, but it is almost captious to raise objections. It is 
a hardy bird, and may remain with us later in the season than the others; 
often a few linger after the gophers have holed up for the winter. Then, of 
necessity, it must turn to other prey, and for a short season may give some 
offence to the poulterer or the game protectionist, for it is powerful if not 
very agile, and has been known to kill birds as large and vigorous as ravens. 
Depredations are usually committed by young and inexperienced birds in 
search of easy prey, but the fact that the species has already spent months 
industriously hunting ground-squirrels and gophers and will do so another 
