Pin-Striped Tit-Babbler feeding a Square-Tailed Drongo-Cuckoo foster chick 

The Drongo Cuckoo is a nest parasite, with the female laying her eggs in the nest of the Pin-striped Tit-babbler. The former is about twice the size of the latter. Within a few days of hatching, the cuckoo chick would have outgrown the host.
It is a sight to behold, seeing the smaller adult feeding the larger fledgling, whose reddish gape is large enough to contain the head of the foster parent. Considering the large size of the chick, the foster parents will have to work flat out to keep the hungry juvenile satisfied.