Buteo Cuv., Lec. Comp. Anat., i, Tabl. Ois., 1800.
Type, Falco buteo Linn.
The genus Buteo contains the Buzzards, which differ from the Eagles in their weaker bills and feet and also in having no true immature plumage beyond slight variations in the barring of the tail and underparts. At the same time individual variation is extreme and is difficult to work out, as neither age nor sex seem to have anything to do with it.
In this genus the bill is moderate or small, the culmen is curved from the cere, the commissure almost straight, the festoon obsolete; the nostrils are oval and oblique; the wings are long, the fourth primary a trifle the longest or about equal to the fifth and third; the first four quills are deeply notched on the inner web ; the tail is rather long and slightly rounded at the end ; the tarsus is long, partly feathered in front with broad transverse scutellae behind ; the toes are short with the inner toe much shorter than the outer.
This genus is found throughout the greater part of the world but does not extend further South-East than India, though North it is represented East to Japan.
The Himalayan Bough-legged Buzzard has been generally separated under the generic name Archibuteo and Kirke-Swann retains the American species under the name Triorchis. The only difference between Buteo and Triorchis consists in the amount of feathering on the legs and as this is only a question of degree it does not seem of generic value. I therefore unite Buteo and Triorchis. It should be noted that Kirke-Swann, though keeping his two genera separate, admits the so-called Archibuteo hemitolophus to be identical with Buteo hemilasius.
Key to Species—Adults.
A.Tail more brown than rufous, with four to twelve transverse bars, not always distinct.
a. Tail with subterminal and seven other bars, the base and inner webs of the rectrices white ; flanks dark brown………….B. hemilasius, p. 140.
A.Tail with four or five nearly obsolete dark bars ; flanks and thighs rufous…………..B. burmanicus, p. 143,
B.Tail more rufous than brown, the bars obsolete with the exception of the subterminal one.
c.Tail bright rufous............... B. vulpinus, p. 142.
d.Tail pale rufous............... B, rufinus, p. 137.
C.Tail uniform brown ............... B. burmanicus, p. 143.
D.Tail brown or ashy-brown with transversebars.
e.Thighs buff streaked with dark brown………………….B. rufinus, p. 137.
f. Thighs ashy-brown, spotted with white………………B. hemilasius, p. 140.
E.Tail rufous, mottled with dark brown……………B. vulpinus, p. 142.
It will be seen from the above key that I follow Kirke-Swann in considering both Buteo burmanicus and Buteo vulpinus should rank as full species.