Steppe Eagle Aquila nipalensis
The western (orientalis) and eastern (nipalensis) subspecies of Steppe Eagle differ in average size but such variation is clinal (Hartert 1913, Hartert & Steinbacher 1936–1938, Dementiev & Gladkov 1951, Cramp & Simmons 1980, Ferguson-Lees & Christie 2001, Clark 2005). Two other characters, plumage coloration and the presence or absence of a nape patch, were not found to vary across the species’ range (Clark 2005). Thus, we follow Clark (2005) in treating Steppe Eagle as a monotypic species.

Clark, W.S. 2005. Steppe Eagle Aquila nipalensis is monotypic. Bull. Br. Ornithol. Club 125: 149–153.

Cramp, S. & Simmons, K.E.L. (eds.) 1980. The Birds of the Western Palearctic. Vol. 2. Oxford University Press, Oxford.

Dement’ev, G.P. & Gladkov, N.A. (eds.) 1951. [Birds of the Soviet Union.] Vol. 1. Moscow. [In Russian; Translated 1966, Israel Program for Scientific Translations, Jerusalem.]

Ferguson-Lees, J. & Christie, D. 2001. Raptors of the world. Christopher Helm, London.

Hartert, E. 1913. Die Vögel der Paläarktischen Fauna. Vol. 2. R. Friedländer & Sohn, Berlin.

Hartert, E. & Steinbacher, F. 1936–1938. Die Vögel der Paläarktischen Fauna. Friedländer & Sohn, Berlin.