Part 11

The well-known bird-photographer, Mr. R. Kearton, was desirous of obtaining a good photograph of a sitting thrush, and as he was afraid that her eggs would be hatched before a fine, sunny day presented itself, had some wooden dummies made. These he painted and varnished to look like those of the thrush, and put them in the nest, wondering whether the bird would be deceived. He need not have wondered; she would probably have sat upon the shams even had they not been coloured.

Upon another occasion Mr. Kearton replaced some starling nestlings by his wooden eggs, and waited to see what would happen. “In a few minutes,” he writes, “back came the starling with a rush. She gazed in wonder at the contents of the nest for a few seconds, but, quickly making up her mind to accept the strangely altered condition of things, she sat down on the bits of painted wood without a trace of discontent in either look or action. Putting her off again, I reversed the order of things and waited. Upon returning, the starling stared in amazement at the change that had come over the scene during her absence; but her curiosity soon vanished, and she commenced to brood her chicks in the most matter-of-fact way.” Then Mr. Kearton took out the chicks and put his fist into the nest, so that the back of his hand was uppermost. The starling actually brooded his knuckles. We must, of course, remember that a starling’s nest is in a hole, where there is but little light. But, provided the starling could not see him, I believe that she would have brooded his knuckles in broad daylight.

Crows, the most intelligent of birds, will sit upon and try to hatch golf balls and ping-pong balls. One famous kite in Calcutta sat long and patiently in a vain attempt to make a pill-box yield a chick, while another member of this species subjected a hare’s skull to similar treatment. Upon one occasion I took a robin’s egg that was quite cold and placed it among the warm ones in a blackbird’s nest. The hen came and brooded the egg along with her own without appearing to notice the addition, although it was much smaller than her eggs and of a totally different colour.

In the same way, if a set of nestlings of another species be substituted for those already in the nest, the parent birds will usually feed the new family without noticing the change. Instinct teaches a bird to brood all inanimate objects it sees in the nest and to feed all living things, whether they be its own offspring or not, and many birds blindly obey this instinct. It is, of course, to the advantage of the species that this should be so. For it is only on very rare occasions that foreign objects get into a nest, and nature cannot provide for such remote contingencies.

Similarly, instinct will not allow a bird to pay any attention to objects outside the nest, even though these objects be the bird’s own offspring.

As everybody knows, the common cuckoo nestling ejects its foster-brethren from the nest, and if the true parents were able to appreciate what had happened, how much sorrow among its victims would the cuckoo cause! As a matter of fact, no sorrow at all is caused. Incredible as it may seem, the parent birds do not miss the young ones, nor do they appear to see them as they lie outside the nest. In this connection I cannot do better than quote Mr. W. H. Hudson, who was able to closely observe what happened when a young cuckoo had turned a baby robin out of the nest. “Here,” writes Hudson, “the young robin when ejected fell a distance of but five or six inches, and rested on a broad, light green leaf, where it was an exceedingly conspicuous object; and when the mother robin was on the nest—and at that stage she was on it the greater part of the time—warming that black-skinned, toad-like, spurious babe of hers, her bright, intelligent eyes were looking full at the other one, just beneath her, which she had grown in her body and had hatched with her warmth, and was her very own. I watched her for hours; watched her when warming the cuckoo, when she left the nest, and when she returned with food and warmed it again, and never once did she pay the least attention to the outcast lying there close to her. There on its green leaf it remained, growing colder by degrees, hour by hour, motionless, except when it lifted its head as if to receive food, then dropped it again, and when at intervals it twitched its body as if trying to move. During the evening even these slight motions ceased, though the feeblest flame of life was not yet extinct; but in the morning it was dead and cold and stiff; and just above it, her bright eyes upon it, the mother robin sat on the nest as before warming the cuckoo.”

Even those actions of nesting birds which appear to be most intelligent can be shown to be merely automatic. Take, for example, the curious habit of feigning injury, which some birds have, when an enemy approaches the young, in order to distract attention from them to itself and thus enable them to seek cover unobserved. This surely seems a highly intelligent act. But birds sometimes act thus before the eggs are hatched, and by so doing actually attract attention to the eggs. This action is purely instinctive, and is perpetuated and strengthened by natural selection because it is beneficial to the race.

We have seen how at the nesting season all a bird’s normal actions and instincts are subordinated to those of incubation. It is therefore but reasonable to suppose the incubating bird to be in a very peculiar and excitable state, a state bordering on insanity.

A bird in this condition might be expected to go into something resembling convulsions on the approach of an enemy, and, provided its acts under such circumstances tended to help the offspring to escape, and were at the same time not sufficiently acute to cause the mother bird to fall a victim to the enemy, natural selection would tend to perpetuate and fix such actions.

Want of space prevents further dilation upon this fascinating subject.

To sum up the conclusions I desire to emphasise. A bird has during the greater part of its life only to look after itself, and the more intelligent it be the better will it do this, hence natural selection tends to increase the intelligence of birds. But, at certain seasons, it becomes all-important to the species that the adults should attend to their young, even at risk to themselves. To secure this Nature has placed inside birds a force, dormant at most times, which at periodic intervals completely overrides all normal instincts, a force which compels parent birds to rivet their attention on the nest and its contents. Thus the sudden conversion of birds into automata is a necessity, not a mere whim of Dame Nature. The instinct is not of very long duration; for as soon as the young are able to fend for themselves, the parents sometimes behave in what seems to human beings a most unnatural way: they drive off their offspring by force. As a matter of fact, this behaviour is quite natural; it is dictated by Nature for the benefit of the species. Strong as the maternal instinct is, it is liable to be overridden by stronger instincts, such as that of migration. When the time for the migratory journey comes round, the parent birds will desert, without apparently a pang of remorse, or even a thought, the broods for whose welfare they have been slaving day and night. This desertion of later broods by migratory birds is far commoner than is generally supposed. In 1826 Mr. Blackwell inspected the house-martins’ nests under the eaves of a barn at Blakely after the autumnal migration of these birds. Of the twenty-two nests under the eaves inspected on 11th November, no fewer than thirteen were found to contain eggs and dead nestlings.

PLAYING CUCKOO

Ornithological experience led me some time back to the belief that at the nesting season a bird becomes a creature of instinct, an organism whose actions are, for the time being, those of a machine, a mere automaton. This view, which has been set forth in the preceding article, is not held by all naturalists. I therefore determined to undertake a systematic series of experiments with a view to putting it to the test. In other words, I decided to play cuckoo. I selected the Indian crow (Corvus splendens) as the subject of my experiments, because it is the most intelligent of the feathered folk. If it can be proved that when on the nest the actions of this bird are mechanical, it will follow that the less intelligent birds are likewise mere automata when incubating. Another reason for selecting the crow as my victim is that I have been investigating the habits of the koel (Eudynamis honorata), which is parasitic on the crow, and in so doing have had to visit a large number of crows’ nests.

The crow lays a pale blue egg blotched with brown, while the egg of the koel is a dull olive-green also blotched with brown. It is considerably smaller than the crow’s egg. I have seen dozens of koel’s eggs, but never one that a human being could possibly mistake for that of a crow, yet our friend Corvus is unable to detect the strange egg when deposited in the nest and sits upon it. It is not that birds are colour-blind. The koel is able to distinguish its own egg from that of the crow, for, after it has deposited its egg, it frequently returns to the nest and removes one or more of the crow’s eggs! I am convinced that ordinarily a crow would have no difficulty in distinguishing between the two kinds of egg; but at the nesting time it throws most of its intelligence to the winds and becomes a puppet in the hands of its instincts, which are to sit upon everything in the nest.

I have myself placed koel’s eggs in crows’ nests, and in every case the crow has incubated the eggs. On one occasion I came upon a crow’s nest containing only two koel’s eggs. As the nest was some way from my bungalow and in an exposed situation, I knew that, the moment I left, it would be robbed by some mischievous native boy, so I took the eggs and placed them in a crow’s nest in my compound. This already contained three crow’s eggs, two of which I moved, substituting the koel’s eggs for them. The crow’s eggs had only been laid three or four days, but the koel’s eggs were nearly incubated, since both yielded chicks on the third day after I placed them in the nest. If nesting crows think, that pair must have been somewhat surprised at the speedy appearance of the chicks!

In all, I have placed six koel’s eggs in four different crow’s nests, and as I have already said, in no single instance did the trick appear to be detected. In the majority of cases, I did not trouble to keep the number of eggs in the nest constant. I merely added the koel’s egg to those already in the nest.

But I have put my theory to a much more severe test. In a certain crow’s nest containing two eggs I put a large fowl’s egg. This was cream-coloured and fully three times the size of the crow’s egg, yet within ten minutes the crow was sitting comfortably on the strange egg. She did not appear to notice the considerable addition to her clutch. She subsequently laid three more eggs, so that she had six eggs to sit upon, five of her own and the large fowl’s egg! Day after day I visited the nest and watched the progress of the strange egg. On the twentieth day the chick inside was moving, but when I went to the nest on the twenty-first day I discovered that some one had climbed the tree, for several branches were broken. Two young crows had been taken away and the fowl’s egg thrown upon the ground. There it lay with a fully formed black chicken inside! I have that chicken in a bottle of spirit. Subsequent inquiry showed that the dhobi’s son had taken it upon himself to spoil my experiment. However, it went sufficiently far to prove that crows may one day become birds of economic value; why not employ them as incubators? Had the crow come across that chick’s egg anywhere but in its nest, it would undoubtedly have made its breakfast off it.

I repeated the experiment in another nest. This time the chick hatched out. When it appeared the rage of the crows knew no bounds. With angry squawks the scandalised birds attacked the unfortunate chick, and so viciously did they peck at it that it was in a dying state by the time my climber reached the nest.

With a view to determining at what stage the incubating instinct secures its dominance, I placed another fowl’s egg in a crow’s nest that was almost ready to receive eggs, wondering whether the presence of this egg would stimulate the crow to lay, without troubling to give the final touches to the nest. The bird devoured the egg. It is my belief that the acts of a nesting bird do not become completely automatic until it has laid an egg in the nest. If one visits a crow’s nest which is in course of construction, the owners will as likely as not desert it; but I have never known a crow desert its nest when once it has laid an egg—provided, of course, he who visits the nest leaves any eggs in it.

In another nest containing two crow’s eggs I placed a golf ball; on returning next day I found the crow sitting tight upon her own two eggs and the golf ball!

But in another case, where I had found two eggs and substituted for them a couple of golf balls, the crow refused to sit. I suppose the idea was, “I may be a bit of a fool when I am nesting, but I am not such a fool as all that!” I once came across a young koel and a crow’s egg in a nest. I removed the former and placed it in a crow’s nest containing four crow’s eggs. The owner of the nest showed no surprise at the sudden appearance of the koel, but set about feeding it in the most matter-of-fact way. The young koel was successfully reared; it is now at large and will next year victimise some crow. I may say that no human being could possibly fail to distinguish between a young koel and a young crow. When first hatched the koel has a black skin, the crow a pink one. The mouth of the crow nestling is an enormous triangle with great fleshy flaps at the side; the mouth of the koel is much smaller and lacks the flaps. The feathers arise very differently in each species, and whereas those of the crow are black, those of the koel are tipped with russet in the cock and white in the hen.

In another nest containing a young koel (put there by me) and two crow’s eggs, I placed a paddy bird’s (Ardeola grayii) egg, hoping that the gallant crow would hatch it out and appreciate the many-sidedness of her family. She hatched out the egg all right, at least I believe she did. I saw it in the nest the day before the young paddy bird was due; but when I visited the nest the following morning neither egg nor young bird was there. It would seem that the crow did not appreciate the appearance of the latest addition to the family and destroyed it. It is, of course, possible that the young koel declined to associate with such a neighbour and killed it; but I think that the crow was the culprit, for I had previously placed a paddy bird nestling, four days old, in a crow’s nest containing only young crows, and the paddy bird had similarly disappeared.

These, then, are the main facts which my game of cuckoo has brought to light. They are not so decisive as I had expected. They seem to indicate that the actions of birds with eggs or young are not quite so mechanical as I had supposed. Were they not largely mechanical a crow would never hatch out a koel’s egg, nor would it feed the young koel when hatched out; it would not incubate a fowl’s or a paddy bird’s egg, and it would assuredly decline to sit upon a golf ball. On the other hand, were the acts of nesting birds altogether mechanical, the young paddy birds would have been reared up, and the substitution of two golf balls for two eggs would not have been detected. There is apparently a limit to the extent to which intelligence is subservient to blind instinct.

THE KOEL

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.