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, kuil, 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 _kūk, kŭū, kŭū, kŭū, kŭū, kŭū_, 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.