BUTEO SWAINSONI, SWAINSON S BUZZARD. 357 



heavy nor so large a bird, aud 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 numerous 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 emarginate primaries, while the Red-tail has /o??r; the fourth quill 

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

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



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

 difference and other variations in size : Largest-adult 9 , 22 inches long, 

 54 in extent, Ihe wing IG ; other females, respectively, 21.50 by 51.75 by 

 16.25; 21.00 by 53.00 by 15.75 ; 20.50 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 15.00 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 tlie old birds the 

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

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

 In the young-of-the-year these yellow parts much duller — grayish-.vellow, 

 or yellowish clay-color. Many old birds have the integument 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 ])arts show the characteristic 

 color and markings of the formerly supposed species, " MirdiiP (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 observations upon a spring monlt, 

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

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

 another supposed species {B. hm(inaiuii) ; 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 female is. This dark plumage is an 

 individual peculiarity, not a normal stage of regular occurrence. 



iSwainson'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 otten 

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

 from which to cast about for some imi)rud('nt goi)lier* espied too Air 

 I'rom home, or still more ignoble game. But the bird jjielers timber, 

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

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

 boundless piaiiie. In Northeiii Dakota such streams cut their tt)rtu()us 

 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 resting-si)ots, where sometimes a line of several 

 birds may he observed strung along a distaiu-e ot a few yards. The 

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



*" Ctopher" : Frontier vemficnlar nanio for all tlio proiind-siinirrels (SpcrwophiU) 

 iudihciiiniiiately. ^'. tndiTcm-i'iKHhin ia tJie Louiuiout'st kiml Llic. Tbu i>oucbed rats 

 arc kuowu as " imckot-gopliera." 



