The intrinsic muscles of the syrinx fixed to the ends of the bronchial semirings; the edges of both mandibles smooth, with a single notch in the upper one; hinder aspect of tarsus smooth, bilaminated; wing with ten primaries; tongue non-tubular ; nostrils clear of the line of the forehead; the lower edge of the nostril nearer to the commissure than the upper edge is to the culmen; plumage of the nestling like that of the adult bird, but paler; nostrils overhung by hairs or plumelets; rictal bristles present; rectrices ten; sexes absolutely alike; an autumn moult only.
The Dicruridae, or Drongos, form one of the best-defined families of the Passeres, their generally black plumage and forked tail of ten feathers sufficing to distinguish them readily.
In the Drongos the plumage of the nestling is a dark brown, which soon gives place to the glossy black of the adult. In many species, however, the young birds, previously to adopting the adult plumage, acquire feathers on the abdomen, under wing-coverts, and axillaries which are tipped or fringed with white, and traces of these white marks remain in one or two species up to a very advanced age, and probably in some specimens are never lost at all.
The Drongos are handsome and, for the most part, familiar birds. They feed habitually on the wing, darting from some perch on a tree into the air to catch an insect and returning to the same or an adjoining branch. The Dicruri frequently perch on the backs of cattle. They all have cheerful notes, and Dissemurus paradiseus has a really fine song, and is perhaps the best singing-bird of the East.
Many of the Drongos, without being exactly migratory, are in many parts of the country subject to seasonal movements of greater or less extent; but the materials for tracing these movements are imperfect, no ornithologist having observed them in the careful manner in which similar movements of birds in Europe are recorded. In Pegu, for instance, Dicrurus ater arrives in great numbers in October and remains numerous till January, when the majority of the birds disappear. Dicrurus annectens similarly arrives in October, but only stops a few days, disappearing entirely and going on to unknown parts.
In all the Dicruridae the wing is tolerably pointed and the tarsus very short.
The Drongos make cup-shaped nests in trees, and lay three to five eggs, which are whitish marked with various shades of red.
Key to the Genera.
a. Outer tail-feathers not greatly Lengthened; not exceeding the middle ones by so much as the Length of the wing.
a1. Forehead not tufted.
a2. Bill deep; depth at nostrils fully equal to width at that place……………DICRURUS, p. 310.
b2. Bill depressed; depth at nostrils much less than width at that place……………CHAPTIA, p. 318.
b1. Forehead tufted.
c2. Tuft composed of a few hairs several inches long……………CHIBIA, p. 320.
d2. Tuft composed of a few hair-like feathers half an inch long……………DISSEMUROIDES, p. 321.
e2. Tuft composed of ordinary feathers half an inch long……………DISSEMURULUS, p. 322.
b. Outer tail-feathers greatly Lengthened; exceeding the middle ones by twice or three times the Length of wing.
c1. Terminal portion of outer tail-feather flat and equally webbed on both sides……………BHRINGA, p. 323.
d1. Terminal portion of outer tail-feather curled, greatly webbed on the outside and hardly at all on the inside……………DISSEMURUS, p. 325.