The drongo is blue and black and is, he believes, warningly coloured.
Pheasants, ducks, geese and snipe are abundant, and Dr C. Collingwood in his Naturalist's Rambles in the China Seas mentions .Ardea prasinosceles and other species of herons, several species of fly-catchers, kingfishers, shrikes and larks, the black drongo, the Cotyle sinensis and the Prinia sonitans.
This suggests that the resemblance to the pugnacious drongo may be beneficial in protecting the defenceless cuckoo from enemies.
He found that a South African drongo (Dicrurus (Buchanga) assimilis) was rejected after one or two attempts to eat it by a hungry mongoose (Herpestes galera) which had been starved for purposes of the experiment.
In this case also both sexes of the cuckoo mimic the drongo, whereas according to the theory it would be necessary for the hen bird alone to do so.