NATURE
Call of the koel

For almost nine months of the year, the Asian koel is seldom seen because it neither sings nor calls except in the breeding season, writes Lt-Gen Baljit Singh (retd) 

THE nightingale, a small brown bird of the UK that fills their nights with mellifluous song during spring, was a favourite of their renaissance poets. When the founding fathers of Indian ornithology, the British, noticed that the koel sang also by night, they nostalgically referred to the bird as "the Indian Nightingale".

It is a pleasant coincidence though that the koel should have had linkages in the Indian culture both with poetry and poets. For, I believe that the great poet Kalidasa had noticed that koels sang with great abandon at the gathering of the monsoon clouds and so devoted a paean to this bird in his epic poem Meghadhoot. And in contemporary Indian history, one of our popular poets, Sarojini Naidu had won popular encomium as "The Nightingale of India" presumably because of the lyricism in her poetry.

Now reverting to our feathered world, the Asian koel (also called the Indian and the common koel) is one of the 20 species that make up our family of cuckoos. Of these, the koel alone has an all-India presence, including the Andaman and Car Nicobar archipelago and the Himalayas up to approx 6,500 ft elevation.

The male koel is coal-black with bluish green gloss, ruby red eyes and a pale green beak. The female can at once be told by the somber brown plumage with olive gloss and white dots on the upper parts. Her belly is off-white with bold brown bars extending to the underside of the tail as well.

For almost nine months of the year, the koel is seldom seen because it neither sings nor calls except in the breeding season which is generally from mid-April to mid-July and therefore remains anonymous and also being exclusively arboreal with propensity to remain inside leafy foliage, it goes undetected, by and large.

But once it comes into the breeding cycle, the male’s penetrating call-cum-song is most audible and unmistakable. He begins with a soft ku...oo... ku...oooo...ku...ooo...rising to the next upper scale with each successive utterance till it reaches the crescendo. The female on the other hand responds simply with a sharp kik...keek...keek. Frankly, it would be hard to find any poetic virtue in that song.

Once the female is ready to lay the clutch of eggs, she communicates this fact to her mate. The pair set out jointly to scout for nest building house crows. The moment they spot a nest with two to three eggs, the male koel begins to intimidate the nesting crow by posing as though he meant to plunder the nest. The crow, of course, will have none of the koel’s bluster and engages him in a long aerial chase.

The female koel grabs the opportunity and hurriedly deposits four to five eggs in the unguarded crows nest. Though smaller but these eggs have the exact shape, colour and speckled pattern as those of the crow’s.

It is not unusual to find 10 to 13 eggs in one crow-nest but again no one knows whether the same koel pair was the depositors of all eggs or other different pairs added to the sum?

Proverbially, cunning though the crow may be but they neither can count nor be wise to the koel’s ruse. So they begin incubating all the eggs, little realising that the koel’s eggs are biologically timed to hatch about 48 hours earlier than their own. To confound the situation deeper, the koel chicks at this stage have the plumage, colour and looks similar to the hatchlings. So the crow parents now have a huge task on their hands to feed may be up to eight foster chicks, masquerading as crow progeny.

This evolutionary prank doesn’t end yet. The koel chicks are born domineering; so to begin with, they recognise and kick out the crow’s yet-to-hatch eggs from the nest. They next tend to grab all or the maximum feed which the crow parents bring to the nest. The under-nourished crow-chicks either remain weaklings or even perish. The sturdier koel fledglings next attempt and often succeed in even pushing the crow chicks from the nest on to the ground below, with fatal consequences.

At the end of this comic and fascinating evolutionary process of propagation of the koel species through what ornithology calls "Brood Parasitism", the crow pair seldom add more than one of their kind, in a season. The Japanese, who over the past two decades have been complaining of burgeoning crow population, need to check on the state of health of their birds who "Brood Parasites" the crow.

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