Dicrurus Vieill., Nouv. Diet. d'Hist. Nat., ix, p. 583 (1817). Type, D. balicassius.
In the genus Dicrurus the bill is stout, sharply carinated and covered at the base by dense short feathers, which partially conceal the nostrils. There is no crest or tuft on the head. The tail is well-forked, the outermost feather exceeding the middle pair by a distance of from once to over twice the length of the tarsus; the outer tail-feathers have a curve upwards, sometimes so slight as to be hardly noticeable.
This genus is one which has hitherto been very unsatisfactorily dealt with; the greater number of the species contained in it range over a very wide area and are therefore subject, as we should expect, to geographical variations, sometimes slight, sometimes very pronounced: Oates treated some of these variations as full species and some he ignored altogether, a position almost certain to arise when subspecies are not recognized but much easier to deal with when the trinomial system is accepted. Under the latter system we can recognize five easily distinguished species, these being again divided into more or less numerous geographical, races.
Key to Species.
A. Upper plumage deep glossy black.
a. Outermost tail-feathers exceeding
central ones by about length of
tarsus and distinctly curved D. annectens, p. 353„
b. Outermost feathers exceeding central pair by more than twice length of
tarsus and only faintly curved D. macrocercus, p.353
B. Upper plumage grey.
c. Lores and sides of head grey.
a1. Lower plumage uniform grey D. leucophaeus, p. 359.
b1. Lower plumage partly white D. caerulescens, p 363.
d. Lores and sides of head white D. leucogenys, p. 367.