Asian koels are shy yet smart birds because they perch on the top branches of a tall tree canopy to keep themselves safe from predators. We often hear the koel’s songs but don’t see the bird that often. But this is not the only smartness of the koel. Unlike most bird species, they do not labour to build their nests to lay eggs, nor do they hatch eggs or labour to raise chicks. They outsource all these jobs. Their breeding season starts in summer. But the female lays her eggs in nests of other birds such as crows, mynas, starlings, etc. when they are not around. In this process of laying eggs, sometimes the female koel pushes some of the eggs of the host bird off the nest or even sometimes eats them. After laying eggs, the female koel leaves it to the host bird to hatch them. The latter generally fails to differentiate between its own eggs and that of the koel and thus obliges. This behaviour of laying eggs in the nests of other birds and abandoning them is known as brood parasitism.
But the ‘cheating’ does not end here. When eggs are hatched and hatchlings come out, the host again fails to recognise that some of the hatchlings are not its own. So, it feeds them like its own chicks. Eventually, the host bird realises that some of the chicks are indeed not its own and abandons them. But by then, most of the koel chicks would have learned to fly and find food on their own.
The crow might be a smart bird but the koel is smarter. The Asian koel couple sits near the nest of a crow and the male tries to annoy the crow. The moment the crows leave their nest to chase the male koel away, the female koel seizes the opportunity and lays her eggs in the crow’s nest. Thus, the latter often gets the former to hatch her eggs and raise the chicks. By the time the poor crow couple realises that their labour of love has benefited someone else, the koel chicks get their wings and fly away. All this while, the koels would be making merry, sitting on branches of mango trees. Once the crows realise this, they abandon the chicks they had been rearing for weeks.
This is an excerpt of an article written by Shefali Naik, Assistant Professor, School of Engineering and Applied Science, first appeared in Indian Express. Professor Naik is a passionate wildlife photographer and a bird watcher.