Even smart guys get duped, and for the House Crow, it is by the Asian Koel ( Eudynamys scolo paceus) . The Koel is a truant parent, and to ensure the survival of its kind takes on the role of a brood parasite of the House Crow. The female Koel slyly approaches the unguarded nest of the House Crow, lays eggs in it, and slips away. It is also said that the male Koel may play a helpful role by distracting the House Crow from the nest to aid the female to lay her eggs. The young that hatch are cared for by the gullible foster parents and escape from the scene as soon as they can take care of themselves. I have seen fledglings of Koel being fed along with young House Crows and sometimes there were only Koel young. This depends on whether the mother Koel was able to remove the crow's eggs (or maybe the nestlings later on) from the nest. Unlike some parasitic cuckoos, the nestlings of Koel are reported not to eject the young of their foster parents.
The Koel is also reported to use the Jungle Crow as its foster parent in some areas, and there are also rare reports of its conning oriole and drongo species. Starling and mynas are their victims in Malaysia. Why has not anybody attempted an in-depth study of the fascinating House Crow-Asian Koel relationship? In fact, this subject was suggested as a topic for a doctoral dissertation by the late Mr. J.C. Daniel (former Director of the BNHS), but the student was not interested, commenting later to me “a PhD on crows”! With surveillance and spy cameras now much more easily available and cheaper, obtaining data for a study would be much easier — any takers?