Prakash Garde of Pune, India, documented the activities of a pair of House Crow (Corvus splendens) building their nest within a short period of seven days. The female then laid a clutch of eggs that subsequently turned bad when the temperature rose above 42º C in the shade on two consecutive days. The crows then built another nest in a nearby tree that yielded three Asian Koel (Eudynamys scolopacea) chicks.
Prakash reported how a group of eight Asian Koels living within the vicinity, four males and four females, kept watch on the crows’ nest. The female koels eventually laid their eggs in the crows’ nest when the latter were not around. This was at about 0545 hours when it was sill dark. The koels (both sexes) kept visiting the nest after laying their eggs. On two occasions they were seen at the nest for sufficiently long durations, with the male seemingly eating something.
When the chicks hatched in the crows’ nest, they were fed regularly by their foster parents. The koels were not observed feeding the chicks.
What was also not observed was the male koel luring the incubating crow from the nest before the female koel sneaked into the nest to lay her egg. Similarly, the removal of the crow’s egg by the koel was not observed. However, there was the possibility of the male koel eating the crow’s egg during the pair’s visit to the nest after the female koel laid her egg.
Another observation was that the iris of the koel chick was black, as compared to the red iris of the adult. Could this be an adaptation to avoid detection by the crows that the chick was not theirs? Prakash argued that as the crows are not able to recognise a koel chick whose plumage is radically different from their own, “it is hard to believe that they would detect the colour of its iris. The changing of the colour of iris in adulthood may, therefore, have some other significance.”
Prakash Garde (2011), A note on the observations of House Crows nests. Newsletter for Birdwatchers 51(1), 2-4.