BUTEO SWAINSONI, SWAINSON's BUZZARD. 357 



heavy nor so large a bird, and its shape differs in some points. A very 

 tangible and convenient distinctiou, to which my attention was tirst 

 called by Mr. Eidgway, and which I have verified in nnmerous in- 

 stances, is found in the emargination of the primaries. As stated in 

 my late work (Key N. A. Birds, p. 217), Swainson's Buzzard has only 

 three emargiuate primaries, while the Eed-tail has/o»)-; thefoarth ouill 

 of the former, like the fifth of the latter, is variously sinuate-tapering, 

 but never shows the decided nick or emaryinatiou of the inner web. 



She following measurements, taken in the flesh, illustrate the sexual 

 difference and other variations in size : Largest adult 2 , 22 inches long, 

 64 in extent, the wing 16 ; other females, respectively, 21.50 by 51.75 bv 

 16.25 ; 21.00 by 53.00 by 15.75 ; 20.60 by 51 .00 by 15.25 ; 19.00 by 49.00 by 

 13.50 — but this last one was an ungrown young. Adult S 's, 19.00 to 

 20.00 long by about 49.00 in spread of wing, the latter 16.00 or a little 

 more. In both sexes, and at all ages, the eye is brown, but of varying 

 shade — I have seen no approach to a yellow iris. In the old birds the 

 feet, together with the cere, gape, and base of under mandible, are rich 

 chrome-yellow ; the rest of the bill, and the claws, being bluish-black. 

 In the young-of-the-year these yellow -paits much duller — grayish-yellow, 

 or yellowish clay-color. Many old birds have the integunieut of the 

 lower belly largely bare, yellowish in color, hardened and thickened 

 with warty excrescences; this disease seems the rule rather than the 

 exception. Unfledged nestlings are covered with white fluffy down ; 

 the first feathers to appear on the under parts show the charactpristic 

 color and markings of the formerly sujjposed species, " hairdii." (The 

 various plumages are given beyond.) A moult occurs in August and 

 September; it is protracted, the feathers being very gradually renewed, 

 almost one by one; the fresh heavily-colored feathers contrasting strongly 

 with the ragged and faded ones worn during the summer. The young 

 have no moult at this season, carrying the plumage in which they leave 

 the nest into the winter. I have no ob.servatious upon a spring moult, 

 which probably occurs to both old and young. I took no specimens in 

 the melanistic state of plumage in which the bird has been described as 

 another supposed species (B. imignatus); and only saw one in which the 

 entire under parts looked as dark, when the bird was sailing over me, 

 as the pectoral band of the adult iemale is. This dark plumage is an 

 individual peculiaritj-, not a normal stage of regular occurrence. 



Swainson's Buzzard may be seen anywhere in the region mentioned — 

 even far out on the prairie, miles away from timber, circling overhead, 

 or perched on the bare ground. In alighting, it generally takes advan- 

 ^ tage of some little knoll commanding a view around, though it often 

 has no more prominent place than the heap of dirt from a badger's hole, 

 from which to cast about for some imprudent gopher* espied too far 

 from home, or still more ignoble game. But the bird prefers timber, 

 and, especially as its nesting is confined to trees, it is most frequently 

 observed in the vicinity of the few wooded streams that diversify the 

 boundless prairie. In Northern Dakota such streams cot their tortuous 

 way pretty deeply into the ground ; and the sharp edges of the banks, 

 lising steep on one side, and on the other stretching away on a contin- 

 uous level, are favorite restiug-spots, where sometimes a fine of several 

 birds may be observed strung along a distance of a few yards. The 

 Souris or Mouse Eiver, a stream of this description, is a. favorite resort, 



'"Gopher" : Frontier vemaenlar name for all the ground-squirrels (SjiermopJtili) 

 indiscriminately. S. tyUhcem-Ti ucatus ia the commonest bind here. The pouched rats 

 are known as " pocket-gophera." 



