110 



NORTH AMERICAN BIRDS. 



specimens, aided by tlie important conclusions of Mr. Hancock (Annals and 

 Magazine of Natural History, 2d ser., XIII, 110; London, 1834), Sclilegel 

 (Falconcs, Musdum d'Hi-sloire Xaturelle des Pays-Bas, 1862), Pelzeln (Ueber- 

 sicht der Geier and Fallvcii der Kaiserlichen omitliologischen Saiunilung, 

 April, I860), and Alfred Newton (History of Britisli Birds, revised ed., part 1, 

 June, 1871, pp. 36-52, and Proc. Acad. Nat. He. Pliiladelpliia, July, 1871, 

 pp. 94, 95), in tiieir important papers bearing upon this subject, which, though 

 they eacli express the peculiar individual views of the writer, together clear 

 up pretty satisfactorily the problem of the number, character, and habitats of 

 the several races, as well as the different phases of variation to which each is 

 subject. 



C482,f. 

 Falco polyagrus. 



6488,2. 



Falco sacer. 



In studying the F. kntarius, I have experienced most discouraging dif- 

 ficulties from the want of sufficient series of tlie Old World races, and from 

 the unsatisfactory character of most descriptions and figures of them, besides 

 being much perplexed by tlie contusion of their synonymy by different 

 authors. In conset^uence of this, my diagnoses of the four races of which 

 alone I liave seen examples may be ^■ery unsatisfactory as regards the 

 diameters by wliich they may be most readily distingui.shed. Having seen 

 the adult of only a single one of these four races, I am therefore compelled to 

 base my diflerential characters upon the immature stages. 



In addition to the four races of F. lanarius characterized above, there are 

 several geogrnpliical ibi'ins belonging to the Old World, cliiefly intertropical 

 Asia and Africa. Tliese are the var. hahijlonicus, Scl. and Irliy, (Gray's Hand 

 List, I, p. 20, No. 173,) of Southeastern Europe and Western Asia ; var. hurha- 

 rus, L. (Gray's Hand List, p. 20, No. 174), of Northern Africa ; and var. 

 tanyptcrns, Liclit. ((Jray's Hand List, No. 175), of both tlie iireceding regions, 

 whicli ]\lr. Giuney writes me "is simply tlie intertropical race of F. lanarius, 

 from which it oiilv diflers in beiii'' of a darker shade throughout. "' The F. 



