3 
The species is somewhat variable in size and proportions, but the 
writer can find no constant difference in measurement to correlate with 
the various races. 
The species is at present considered in the A.O.U. Check-list, and by 
most present-day authors, to be composed of the following subspecies: 
Buteo borealis borealis f'GmelinJ, Eastern Red-tail 
Buteo borealis calurus (CassinJ, Western Red-tail 
Buteo borealis krideri Hoopes, Krider’s Hawk 
Buteo borealis harlani ( Audubon,) , Harlan’s Hawk 
Buteo borealis alascensis Grinned, Alaska Red- tail 
BUTEO BOREALIS BOREALIS, EASTERN RED-TAIL 
Single-phased. Adult — upper parts rich, dark brown; lower surface 
white to cream, with more or less dark, streaked flanks, broken abdominal 
band, and in some cases dark throat; tail brick red, usually with black, 
subterminal band (Plate II, figure 5). 
The principal characteristic of this, the type form of the species, in 
comparison with the other races, is its constancy, there being only a single 
phase over most of its range and comparatively little individual variation. 
Some birds are more creamy than others or even slightly rufous below, 
and some are without the subterminal black tail band (Plate I, figure 1), 
but there is not the great variation of colour that is so notable in the western 
forms. Contrary to commonly accepted opinion, highest plumaged adults 
in many cases show perceptible purplish reflections on the back. 
The adult always has a red, unbarred tail (Plate I, figures 1, 2). Juven- 
iles always have dark brownish or blackish tails with black bars (Plate I, 
figure 3); occasionally with a faint admixture of reddish. The back is 
brownish black (blacker than in adult) with more or less concealed white 
feather edges, bases, and spots. Below is largely white with little 
suggestion of cream, but with a broken abdominal band of blackish brown 
and flank patches of similar colour. 
BUTEO BOREALIS CALURUS, WESTERN RED-TAIL 
Double-phased, with all intergrades between the two extremes. Dark 
phase — practically blackish brown, sometimes with reddish or chestnut 
suffusion on breast. Tail of adult brick red, usually with 10 to 12 sharp 
black bands. Juvenile form is not certainly known, but is assumed to be 
as most juveniles of the other forms, blackish with black bars (Plate I, 
figure 8). Light phase-like B. b. borealis, but with decided tendencies 
towards rufous and brown below, considerable barring on flanks, abdomen, 
and flags. Tail red, black barred. Juvenile like juvenile of borealis, but 
more heavily coloured below. 
The Western Bed-tail shows a most remarkable range of colour. 
It was originally described from an almost solidly black bird with red, 
black-barred tail (Plate III, figure 1). This melanotic type intergrades 
perfectly with typical borealis . Calurus has three distinctive characters 
in the adult, any one or more of which may be absent: general blackness 
or melanism, chestnut or reddish areas on breast and elsewhere, and black 
bars across a red tail. Any one of these characters when present in pro- 
nounced degree is sufficient to designate calurus with reasonable certainty. 
