This cuckoo, like many of its relatives, does not hatch its own eggs. It cuckolds crows. This is no mean performance, for the crow is a suspicious creature. It knoweth full well the evil which is in its own heart, and so, judging others by itself, watches unceasingly over its nest from the time the first egg is deposited therein until the hour when the most backward young one is able to fly. Now, a koel is no match for a crow in open fight, hence it is quite useless for the former to attempt by means of force to introduce its egg into the crow’s nest. It is obliged to resort to guile. The cock entices away the crows, and while they are absent the hen deposits her egg.
Crows appear to dislike the cry of the koel quite as much as men do. But whereas man is usually content with swearing at the noisy cuckoo, crows attack it with beak and claw whenever an opportunity offers. This fact is turned to account by the koel. The cock alights in a tree near a crow’s nest and begins to call. The owners of the nest, sooner or later, “go for” him. He then takes to his wings, continuing to call, so as to induce the crows to prolong the chase. As he is a more rapid flier than they, he does not run much risk. While the irate corvi are in pursuit, the hen koel, who has been lurking around, slips into the nest and there lays her egg. If she is given time she destroys one or more of those already in the nest. She does this, not because the crows would detect the presence of an additional egg, but in order that her young, when hatched, will not be starved owing to the large number of mouths to feed.
Crows, although such clever birds, are, as we have seen, remarkably stupid at the nesting season. They are unable to distinguish the koel’s egg from their own, although the former is considerably smaller, with an olive-green background instead of a bluish one; and when the young koel emerges from the egg, they are unable to differentiate between it and their own offspring, although baby koels are black and baby crows pink, when first hatched out. The koel nestling has one point in common with young crows, and that is a large mouth of which the inside is red. This is opened wide whenever a parent approaches, so that the latter sees nothing but a number of yawning caverns; thus there is some excuse for its failure to distinguish between the true and the spurious nestlings.