The Plaintive Cuckoo (Cacomantis merulinus) is a species of bird belonging to the genus Cacomantis in the cuckoo family Cuculidae. It is native to Asia, fromIndia and China to Indonesia.
It is a fairly small cuckoo, 21-23.5 centimetres long. The adult male is grey-brown above and orange below with a grey head, throat and upper breast. There are white tips to the tail feathers. The legs and feet are yellow, the eye is red and the bill is black above and yellow below. The adult female is sometimes similar to the male but often occurs in a "hepatic" morph. This form is reddish-brown above with dark bars. The underparts are paler with fainter barring. There is a pale stripe over the eye and the tail has dark bars along its whole length. Juvenile birds are similar to hepatic females but are paler and have dark streaks rather than bars on the crown and throat.
The male has several plaintive whistling calls. These include an ascending series of three-note phrases and a series of 11 or 12 descending notes.