The South West Monsoon has set in and the nippy mornings are punctuated by the mellifluous call of the cuckoo. The bird has been the muse of great poets and writers and cuckoo songs are associated with rains. But have you ever noticed a cuckoo tailing a crow in your neighbourhood. The sight is most likely to take place in the monsoons, when crows start nesting. “Koels and Cuckoos are cousins belonging to the same family. Both the birds lay eggs in the nests of host birds,” says N. Raveendran, a city-based birder. “Koels are entirely dependent on house crows. They have also become common neighbourhood birds over the years. They are parallel bird communities that co-exist. But they have a love-hate relationship.”
The Asian Koel is a crafty avian parasite that’s a dominant aggressive survivor. “It’s a brood parasite. The parent birds would push the eggs of the host to accommodate their eggs. In some cases, even the newly hatched chick pushes the host’s egg off the nest,” reveals Raveendran. “It was startling to see this happen at a nest in the city outskirts. The incubation period of cuckoos is 13 to 16 days and the period for crows is 17 to 20 days. That’s how the cuckoo chicks hatch earlier than crows.”
The entire process of this parasite nesting precedes the rains. That’s when the crows pair and build nests. The male koel is jet black in colour that’s a keen observer of the crows. It’s he who sings beautifully. Birders and researchers have recorded over 16 different calls by males while females emit only two kinds of calls. The female has a pattern of grey freckles on its body. “The male sings to attract the females. It’s also an announcement that the crows have started nesting. The call will be a long, different from the usual short notes,” explains Raveendran. The male bird follows a strategy where he distracts the crow parents and diverts their attention from the nest. Using the opportunity, the female Koel would sneak in and lay its egg. “Female Koels have the ability to contain the eggs inside body and delay them from coming out.”
When the young ones hatch, they mimic the crow. Only when they grow big enough to take their first flight, they start singing and the crow would chase them away. “The crow out of parental instinct would feed them. Sometimes, after identifying the crow may abandon the nest,” says Raveendran. “Generally, crow is considered an intelligent bird but the Koel is highly clever and crafty.” The parents would keep a watch over the host nests. If the host doesn’t take good care of the chicks, the male koel would destroy the entire nest. The maximum survivor will be the koel as it’s a dominant species,” he adds.
Both cuckoos and Koels are found in India. The Common Hawk Cuckoo, called as the ‘Brain Fever Bird’ due to the peculiarity of its call and Pied Cuckoo, called ‘Akka Kuyil’ in Tamil, are also aggressive brood parasites. Greater Coucal and Southern Coucal are the only members of the Cuckoo family that build their own nests. “They usually roost in the bushes and feed their young ones with the chicks of other birds.”
Cuckoos are partial migrants and residents of tropical forest. They have many hosts such as common mynah, sterlings, Iora, Yellow Billed babbler and jungle babblers, while crow is the only host for Koels. “Koels generally avoid the Jungle crow’s nest,” says Raveendran. “Once I came across an injured female koel in my backyard. Most probably it was attacked by a jungle crow. It must have been caught red handed while laying eggs in the host nest.” Koels are omnivorous and they feed on catterpillars and insects for proteins. However, fruits form their staple diet. They exhibit high adaptability like crows and are found mostly in green areas and temple gardens in Madurai.
So what could be reason for the Asian Koel possessing such a contrasting image to its portrayal? “Probably, the role of brood parasite species is to check the population of common birds like the crow,” suggests Raveendran.