Birds belonging to the Cuckoo family (e.g. asian koel and grey-bellied cuckoo) are brood parasites. They lay their eggs in others birds nests, tricking them into believing that the hatchlings are their own.
This can often result in bizarre ‘mother’ bird /fledgeling pairings !
For the full story, more images and video go to: ‘A Cuckoo Tail-or what you will…’