Erythropus Brehm, lsis, 1828, p. 1270.
Type, Falco vespertinus Linn. Province St. Petersburgh.
The genus Erythropus seems to be the connecting-link between the genera Falco and Cerchneis, having some characters of both the former and the latter, whilst in coloration it is somewhat intermediate between the Hobby and the Kestrel.
The bill is intermediate in size and strength between Falco and Cerchneis and is notched as in Falco; the middle toe is fairly long, a little shorter than the tarsus and the lateral toes are about equal. The wing is long and pointed, the second primary longest and the first longer than the third; the tail is rather long and rounded but not so long ami strongly graduated as in the Kestrels.
Colour of sexes dissimilar.
The Indian or Eastern bird has generally been considered merely a race of the European bird E. vespertinus but Sushkin has pointed out to me that there are no specimens showing inter-gradation between the two and their status seems to be that of representative geographical species rather than subspecies.