THE FORMS OF THE BLACK HAWK-EAGLE 



By HERBERT FRIEDMANN 



Curator, Division of Birds, U. S. National Museum 



(With One Plate) 



The black hawk-eagle, Spizaetus tyrannus (Wied), has always been 

 considered as a species with no geographic races, and, indeed, I so 

 assumed it to be a number of years ago when working on this genus 

 for the eleventh volume of Ridgway's "Birds of North and Middle 

 America." However, recently I have had occasion to examine far 

 more extensive material than was formerly available, and I find, quite 

 contrary to my earlier opinion, that there are two morphologically 

 separable geographic units in the species. The type of tyrannus came 

 from Ilha do Chave, below Quartel dos Arcos, Rio Belmonte, Bahia, 

 Brazil, and the only other names applied to the species are likewise 

 based on eastern and southeastern Brazilian birds — Harpyia braccata 

 Spix (Avium species novae . . . vol. i, p. 7, pi. 3, 1824 ( = 1825)) 

 from Sao Paulo, Brazil, and Spizaetus spixii Des Murs (Rev. Zool., 

 vol. 10, p. 325, 1847) which is merely a new name for H. braccata 

 Spix. 



Birds from Mexico and Central America, and from northern and 

 western South America, south to Para, the Am.azon Valley, and west- 

 ern Brazil (Rio Puriis and Rio Jurua and Mato Grosso) and Bolivia 

 are different from specimens from Bahia, Espirito Santo, Rio de 

 Janeiro, Santa Catharina, Minas Gerais and Sao Paulo in eastern and 

 southeastern Brazil, and for them is proposed the name 



Spizaetus tyrannus serus, new subspecies 



Type.—U.S.1<IM. No. 206391, ad. cf, collected at Rio Indio, near 

 Gatun, Canal Zone, Panama, March 4, 191 1, by E. A. Goldman (orig. 

 No. 13928). 



Subspecific characters. — Similar to the nominate race but with the 

 flanks and thighs more heavily marked with white cross bars, and 

 with the under wing coverts much more whitish, less blackish ; these 

 feathers white, rather sparingly marked with blackish in serits, and 

 almost wholly black in tyrannus. Size of serus averaging smaller than 

 the nominate race. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. Ill, NO. 16 



