Description

Colour Adult:

C.v. vasa: Male-grey/black, more grey on upperparts; grey undertail coverts, shafts of feathers streaked black; outer webs of primary feathers blue/grey; brown/black tail, grey underneath. Bill pink/horn coloured. Lores and eye ring bare and pink/white. Eye dark brown.  Female-as in male but when breeding loses feathers from head to reveal yellow/orange skin.
C.v. drouhardi: Both adults paler, more blue/grey on upperparts; grey/white undertail coverts and underside of tail; tail with darker subterminal band; smaller in size.
C.v. comorensis: Both adults paler in colour; brown tinged underparts; undertail coverts grey/brown with shafts streaked darker; smaller in size.

Colour Juvenile:

As in adult but more brown plumage; feathers of underparts marked chestnut brown. Bill grey. Cere, lores, and eye ring bare and pale grey.

Call:

Wide range of sounds.  Whistling, puppy-like yapping, harsh squawks, raucous calls, and vibrating, grating sounds.