ANGLO-INDIANS frequently confound the koel with the brain-fever bird. There is certainly some excuse for the mistake, for both are cuckoos and both exceedingly noisy creatures ; but the cry of the koel (Eudynamis honorata) bears to that of the brain-fever bird or hawk-cuckoo (Hierococcyx varius) much the same relation as the melody of the organ-grinder does to that of a full German band. Most men are willing to offer either the solitary Italian or the Teutonic gang a penny to go into the next street, but, if forced to choose between them, select the organ-grinder as the lesser of the two evils. In the same way, most people find the fluty note of the koel less obnoxious than the shriek of the hawk-cuckoo.
The latter utters a treble note, which sounds like " Brain fever." This it is never tired of repeating. It commences low down the musical scale and then ascends higher and higher until you think the bird must burst. But it never does burst. When the top note is reached the exercise is repeated.
The koel is a bird of many cries. As it does not, like the brain-fever bird, talk English, its notes are not easy to reproduce on paper. Its commonest call is a crescendo kuil, kuit, kuil, from which the bird derives its popular name. This cry is peculiar to the cock. The second note is, to use the words of Colonel Cunningham, "an outrageous torrent of shouts, sounding like kuk, kuu, kuu, kuu, kuu, kuu, repeated at brief intervals in tones loud enough to rouse the ' Seven Sleepers.'" The koel is nothing if not impressive. He likes to utter this note just before dawn, when all the world is still. As the bird calls chiefly in the hot weather, when it frequently happens that the hour before sunrise is almost the only one in the twenty-four in which the jaded European can sleep, this note is productive of much evil language on the part of the aforesaid European.
The koel's third cry is well described by Cunningham as a mere cataract of shrill shrieks -: heekaree, karees. This is heard mostly when the hen is fleeing for dear life before a pair of outraged crows. So much for the voice of the koel, now for a description of the singer. The cock is a jet-black bird with a green bill and a red eye. The hen is speckled black and white, with the eye and beak as in the cock. Add to this the fact that the koel is a little larger than the " merry cuckoo, messenger of spring " which visits England, and it is impossible not to recognise the bird.
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.
To return to the koel who is laying her egg in the momentarily deserted nest. She does not carry her egg thither in her beak as the common cuckoo is said to do, but sits in the nest and lays it there. Sometimes the crows return before she is ready and, of course, attack her, but as she can fly faster than they, they do not often succeed in harming her, although there are instances on record of crows mobbing female koels to death. It will thus be seen that cuckolding crows is dangerous work. The life of the cuckoo is not all beer and skittles, and the birds seem to feel the danger of their existence, for at the breeding season they appear to be in a most excited state, and are manifestly afraid of the crows. This being so, I am inclined to think that the latter are responsible for the parasitic habit of the koel. It is not improbably a case of the biter bit. Crows are such aggressive birds that they are quite capable of evicting any other bird from its nest if this be large enough to suit their purpose. Now suppose a koel to be thus evicted by force when ready to lay; it is quite conceivable that she might make frantic efforts to lay in her rightful nest, and if she succeeded, and the crows failed to detect her egg, they would hatch out her offspring. If the koels which acted thus managed to have their offspring reared for them, while those that attempted to build fresh nests dropped their eggs before the new nurseries were ready, natural selection would tend to weed out the latter and thus the parasitic habit might arise, until eventually the koel came to forget how to build a nest.
In this connection it is important to bear in mind that the nearest relatives of the koel are non-parasitic. It is therefore not improbable that in the koel the parasitic habit has an independent origin.
This instinct has undoubtedly been evolved more than once. It does not necessarily follow that similar causes have led to its origin in each case.
The suggestion I have made is made only with reference to the koel, which differs from other cuckoos in that it dupes a bird stronger and bigger than itself. But this is a digression.
If the koel have time, she destroys one or more of the existing eggs, and will sometimes return later and destroy others. Although the crow cannot distinguish between her own and koel's eggs, the koel can. I have come across several crows' nests which each contained only two koel's eggs.
The young koel is a better-behaved bird than some of its relations, for it ejects neither the eggs still in the nest when it is hatched nor its foster-brethren. But the incubating period of the koel is shorter than that of the crow, so that the koel's egg is always the first to hatch out. The koel seems never to make the mistake of depositing its egg among nearly incubated ones. Thus the young koel commences life with a useful start on its foster-brethren. It soon increases this start, as it grows very fast, and is ready to fly before the earliest feathers of its foster-brothers are out of their sheaths.
It does not, however, leave its foster-parents when able to fly. It sits on the edge of the nest and makes laudable, if ludicrous, efforts at cawing. The crows continue feeding it long after it has left the nest, looking after it with the utmost solicitude. A young koel is somewhat lacking in intelligence; it seems unable to distinguish its foster-parents from any other crow, for it opens its mouth at the approach of every crow, evidently expecting to be fed.
The natives of the Punjab assert that the hen koel keeps her eye on the crow's nest in which she has laid her egg or eggs during the whole of the time that the young cuckoo is in it, and takes charge of her babe after it leaves the nest. This assertion appears to be incorrect. I have never seen a koel feeding anything but itself. Moreover, the koel lays four or five eggs, and these are not usually all deposited in one nest. It would therefore be exceedingly difficult, if not impossible, for the hen to keep an eye on each of her eggs.
In view of the hatred which crows display towards koels in general, naturalists have expressed surprise that the young koels are not mobbed directly they leave the nest. Their plumage differs in no way from that of the adult. It has been suggested that young koels retain the crow smell for a considerable time after they are fledged. This I cannot accept. The olfactory organ of birds is but slightly developed. Indeed, I am inclined to wonder whether birds have any sense of smell. The truth of the matter is that crows look after their foster-children most carefully for several weeks after they have left the nest, and see that no strange crow harms them.