Biological science is at present in a rather peculiar position. Biologists are divided into two parties. On the one side stand the theorists and their followers; on the other the practical men who think for themselves. At present, the theorists are the party in power (and they are quite Lloyd-Georgian in their methods), while the practical men, the breeders and the field naturalists, form the opposition. The reason of the division is that many facts, that have come to light lately, do not fit in with the theories that hold the field.
Now, when facts are discovered which militate against a theory the proper course for the holder of the theory is to test carefully the alleged facts, and if they prove to be really facts to discard or modify his theory.
Unfortunately the professional biologists of to-day do not usually follow this course. They have made fetishes of their theories, which they worship as the Israelites worshipped the golden calf. The consequence is that they feel in honour bound either to ignore or to gloss over the facts that are subversive of their fetishes. When they write books in honour of their fetishes, theyomit many facts which tend to show that their fetishes are shams. They regard the discussers of the awkward facts as enemies to be crushed. Hence the gulf between the two classes of biologists.
One of the fetishes of the present day is the theory of protective mimicry. Butterflies and moths are the organisms which exemplify best this theory.
It often happens that two species of butterfly occur in the same locality which resemble one another in outward appearance. In such cases zoologists assert that one species mimics the other. They maintain that this mimicry has been brought about by natural selection, because the one species profits by aping its neighbour. The species that is copied is said to be unpalatable. The copy-cat, if I may use the expression, may be either palatable or unpalatable. In either case it is believed to profit by the resemblance. If it is edible the birds that are supposed to prey upon butterflies are said to leave it alone, because they mistake it for its unpalatable neighbour. This resemblance of an edible form to an unpalatable one is called Batesian mimicry.
If the copy-cat be unpalatable it is nevertheless said to profit by the likeness, because young birds are supposed to feed on every kind of butterfly and only to learn by experience which are unpalatable. The theory is that if they attack a red-coloured butterfly and find it nasty to the taste, they leave all red-coloured butterflies alone henceforth. Thus, the imitating species may benefit by the sacrifice of the other red-coloured species. This is known as Mullerian mimicry.
The mimicry theory is very enticing; indeed, it is so enticing that those who hold it, as, for example, Professor Poulton, of Oxford, seem to think that theremustbe something wrong with the evidence opposed to it.
I assert that it is not the evidence against the theory, but the theory itself that is wrong.
The objections to the hypothesis are many and weighty. Finn and I summarised most of them inThe Making of Species.
Two of the objections appear to be insuperable.
The likeness cannot be of much use until it is fairly strong. How, then, is the beginning of the resemblance to be explained?
In order that natural selection should have produced these astounding resemblances, it is necessary that butterflies should be preyed on very largely by birds; but all the evidence goes to show that birds very rarely eat butterflies. In the course of some ten years spent in India I have not seen butterflies chased by birds on more than a dozen occasions. Similarly, Colonel Yerbury, during six years’ observation in India and Ceylon, can record only about six cases of birds capturing, or attempting to capture, butterflies. Colonel C. T. Bingham, in Burma, states that between 1878 and 1891 he on two occasions witnessed the systematic hawking of butterflies by birds, although he observed on other occasions some isolated cases.
Nor is the evidence, as regards India, confined to the experience of the casual observer. Mr. C. W. Mason, when supernumerary entomologist to theImperial Department of Agriculture for India, conducted a careful enquiry into the food of birds. The enquiry was made at Pusa in Bengal, in the years 1907, 1908, 1909. The results arrived at by Mr. Mason are published in theMemoirs of the Department of Agriculture for India(Entomological Series, Vol. III, January, 1912). As the result of this enquiry, in the course of which the contents of the stomachs of hundreds of Indian birds were examined, Mr. Mason writes (page 338,loc. cit.): “Butterflies do not form any appreciable proportion of the food of any one species of bird, though a good many birds take these insects at times. . . .
“The butterflies include a number of minor pests, of whichMelanitis ismenewas taken byMerops viridisandPapilio pammonbyAcridotheres tristis. Other well-known pests arePieris brassicae,Virachola isocratesandPapilio demoleus.Belenois mesentina, a Pierid, was seen to be taken on one occasion by the king-crow, andIlerda senabyPasser domesticus, both of which insects are neutral.
“Moths include many major pests of varied habits—defoliators, miners, cut-worms, grain and fabric pests. The larvae form an inexhaustible supply of insect food to almost all species of insectivorous birds, and even many species of birds that when mature feed almost, if not quite, entirely on grain and seeds are when in the nest fed very largely on caterpillars by the parent birds.”
Obviously, then, in India birds comparatively rarely attack butterflies; but they devour millionsof caterpillars. It is the same in other parts of the world.
Mr. G. A. K. Marshall, in the course of five years’ observation in South Africa, recorded eight cases of birds capturing butterflies.
Similarly Mr. Banta points out in various issues ofNature, in 1912, that all the evidence available shows that in North America birds very rarely capture butterflies. Field naturalists scarcely ever witness a butterfly chased by a bird. Of 40,000 stomachs of birds examined very few were found to contain remains of butterflies.
In 1911 the butterflies of the speciesEugonia californicawere so numerous that “the ground was often blackened with them, and great swarms of them filled the air from morning to evening.” Yet of the birds in the locality where those butterflies were most numerous, only five out of forty-five species were found by direct observation and stomach examination to eat the eugonia, and the only bird that fed off them copiously was the brewer blackbird (Euphagus cyanocephalus) which is almost omnivorous, and eats insects of all kinds, even if they be what Darwinians call warningly coloured!
Now, modern theorists, as a rule, ignore facts such as these, and this certainly is the wisest course they can pursue, unless they are ready to give up these theories or make themselves look foolish.
However, I am glad to be able to record that Professor Poulton has, as regards the remarks of Mr. Banta, not followed the usual course of the modern theorist.
He has had the courage to take up the cudgels and reply to Mr. Banta inNature. The reason of this unusual course appears to be that Mr. C. F. M. Swynnerton has made some observations in South Africa which Professor Poulton considers are in favour of his pet theory.
According to the Professor, Mr. Swynnerton, as the result of three and a half years’ investigation in South-East Rhodesia, “has obtained the records of nearly 800 attacks made by 35 species of birds belonging to 30 genera and 18 families, upon 79 species of butterflies belonging to 9 families or sub-families.”
Professor Poulton does not seem to see that the researches of Mr. Swynnerton are altogether subversive of the theory of protective mimicry. In order that natural selection may totally change the colouring of a butterfly (as it does according to the theory of protective mimicry), that butterfly must be habitually preyed upon by large numbers of birds, which must be so vigilantly and unceasingly on the look-out for it, that its only chance of escaping from their attacks must be for it to assume a disguise.
Compare with this the state of affairs revealed by Mr. Swynnerton’s observations. He worked for three and a half years, and, as his investigations extended to eighteen families of birds, they must have been very extensive. Exactly how extensive they have been we do not know, because he has not yet published them. Nevertheless, as the result of three and a half years’ watching and stomach examination he has evidence of only “nearly 800” attacks madeby birds on insects; that is to say, on an average about two attacks in three days!
Watch a bee-eater feeding and you will see it take twenty or thirty insects in less than an hour. If you were to watch it one whole day you might see it capture 300 insects, but certainly not more than one of its victims, on an average, would be a butterfly. Yet, the theory of mimicry is based upon the assumption that butterflies are so greatly preyed upon by birds that they require special means of protection!
I ask all who are interested in the subject to be ever on the look-out for birds chasing butterflies or moths. These are so large and so easy to identify that there can be no chance of mistaking them. Even a casual observer, when watching a bird, cannot fail to notice the capture of a butterfly by it. And when a bird has captured a butterfly it cannot dispose of it very quickly. According to Mr. Swynnerton, “some (birds) swallow the insect (butterfly or moth) whole, but usually after masticating or beating it; some remove inconvenient portions by ‘worrying’ like a dog or beating against perch or ground; some grasp the prey in one foot and tear off the rejected portions with the bill, eating the rest piecemeal.”
The fact that the average bird has to go through all the above performances before devouring a creature containing so little nourishment as a butterfly, is sufficient to show that it does not pay birds to chase butterflies.
But it is best not to rely on arguments to refute the theories of persons who have no logic in them.The only way to destroy the pernicious zoological theories that hold the field at present is to pile up the facts that tell against them. Similarly, theories that are true cannot be established satisfactorily except by the accumulation of facts. The relations between birds and butterflies can be determined only by observation, and for that kind of observation no country presents a better field than India. Moreover, such observations can be conducted by people having little or no scientific knowledge.
The stillness of the Indian night suffers many interruptions.
In the vicinity of a town or village the hours of darkness are rendered hideous by the noises of human beings and of their appendages—the pariah dogs. In the jungle the “friendly silences of the moon” are continually disturbed by the bark of the fox, the yelling of the jackal, or the notes of the numerous birds of the night.
The call of the various nocturnal birds must be familiar to every person who has spent a hot weather in the plains of Northern India and slept night after night beneath the starry heavens. With the calls of the birds all are familiar, but some do not know the names of the originators of these sounds.
First and foremost of the fowls that lift up their voices after the shades of night have fallen are the tiny spotted owlets (Athene brama). Long before the sun has set these quaint little creatures emerge from the holes in which they have spent the day, and treat the neighbours to a “torrent of squeak and chatter and gibberish” which is like nothing else in the world, andwhich Tickell has attempted to syllabise as “Kucha, kwachee, kwachee, kwachee, kwachee,” uttered as rapidly as the little owlets’ breath will allow of. These noisy punchinellos are most vociferous during moonlit nights, but they are by no means silent in the dark portion of the month.
Almost as abundant as the spotted owlet is another feathered pigmy—the jungle owlet (Glaucidium radiatum). This species, like the last, calls with splendid vigour. Fortunately for the Anglo-Indian its note is comparatively mellow and musical. It is not altogether unlike the noise made by a motor cycle when it is being started, consisting, as it does, of a series of disyllables, low at first with a pause after each, but gradually growing in intensity and succeeding one another more rapidly until the bird seems to have fairly got away, when it pulls up with dramatic abruptness. The best attempt to reduce to writing the call of this bird is that of Tickell: “Turtuck, turtuck, turtuck, turtuck, turtuck, turtuck, tukatu, chatuckatuckatuck.” This owlet calls in the early part of the night and at intervals throughout the period of darkness, and becomes most vociferous just before the approach of “rosy-fingered dawn.”
Very different is the cry of the little scops owl (Scops giu). This bird has none of that Gladstonian flow of eloquence which characterises the spotted and the jungle owlets. His note is, however, more befitting the dignity of an owl. He speaks only in monosyllables, and gives vent to those with great deliberation. He sits on a bough and says “wow” in a soft but decisivemanner. When this pronouncement has had time to sink into the ears of his listeners, he repeats “wow,” and continues to sound this impressive monotone at intervals of a minute for several hours.
The above are the three owls which are most often heard in the plains of Northern India. Sometimes all three species, like the orators in Hyde Park, address the world simultaneously from neighbouring trees.
There are numbers of other owls that disturb the stillness of the night with more or less vigour, but it would be tedious, if not impossible, to describe them all. It must suffice to make mention of the low, solemn boomingdurgoon durgoon, of the huge rock-horned owl (Bubo bengalensis) and the wheezy screech of the barn owl (Strix flammea).
Another call, often heard shortly before dawn, is doubtless usually believed to be that of an owl. This is the deep,whoot, whoot, whootof the coucal or crow pheasant (Centropus sinensis), that curious chocolate-winged black ground-cuckoo which builds its nest in a dense thicket.
Unfortunately for the peace of mankind the coucal is not the only cuckoo that lifts up its voice in the night. Three species of cuckoo exist in India which are nocturnal as owls, as diurnal as crows, and as noisy as a German band. A couple of hours’ sleep in the hottest part of the day appears to be ample for the needs of these super-birds. From this short slumber they awake, like giants refreshed, to spend the greater portion of the remaining two-and-twenty hours in shrieking at the top of their voices.
Needless to state these three species are the brain-fever bird, the koel, and the Indian cuckoo—a triumvirate that it is impossible to match anywhere else in the world. Some there are who fail to distinguish between these three giants, and who believe that they are but one bird with an infinite variety of notes. This is not so. They are not one bird, but three birds. Let us take them in order of merit.
The brain-fever bird or hawk cuckoo (Hierococcyx varius) isfacile princeps. In appearance it is very like a sparrow-hawk, and, but for its voice, it might be mistaken for one. This species has two distinct notes. The first of these is well described by Cunningham as a “highly pitched, trisyllabic cry, repeated many times in ascending semitones until one begins to think, as one sometimes does when a Buddhist is repeating his ordinary formula of prayer, that the performer must surely burst.” But the brain-fever bird never does burst. He seems to know to a scruple how much he may with safety take out of himself. It is not necessary to dilate upon this note. Have we not all listened to the continued screams of “brain-fever,brain-fever,Brain-fever,” until we began to fear for our reason? The other call is in no way inferior in magnitude. It consists of a volley of single descending notes, uttered with consummate ease—facilis descensus—which may or may not, at the option of the performer, be followed by one or more mighty shouts ofBrain-fever. There is not an hour in the twenty-four during the hot weather when this fiend does not make himself heard in the parts of the country hauntedby him. His range extends from Naini Tal to Tuticorin and from Calcutta to Delhi. Assam, Sind, and the Punjab appear to be the only portions of India free from this cuckoo.
The second of the great triumvirate is the Indian koel (Eudynamis honorata). This noble fowl has three calls, each as powerful as the others.
The first is a crescendoku-il, ku-il, ku-il, very pleasing to Indian ears, but too powerful for the taste of Westerns. The second is well described by Cunningham as an outrageous torrent of shouts, sounding “kuk, kŭū, kŭū, kŭū, kŭū, kŭū,” repeated at brief intervals in tones loud enough to wake the seven sleepers. When the bird thus calls its whole body vibrates with the effort put forth. The third cry is uttered only when the koel is being chased by angry crows, and is, as Cunningham says, a mere cataract of shrill shrieks: “Hekaree, karee.”
For the benefit of those unacquainted with the ways of the koel it is necessary to state that that bird spends much of its time fleeing before the wrath of crows. It lays its eggs in the nests of these. And, if one may judge from their behaviour, they suspect the koel. The other two calls are heard at all hours of the day and night, and it makes no difference to the koel whether it is the sun or the moon, or only the stars that are shining. He is always merry and bright. The second call, however, is usually reserved for the dawn. Hence this particular vocal effort is rendered all the more exasperating, coming as it does precisely at the time when, after the departure of a“sable-vested night” straight from Dante’s Inferno, which has been embellished by the sluggishness of thepunkawalla, a certain degree of coolness sets in to give some chance of a little refreshing sleep. Then is it that the jaded dweller in the plains, uttering strange oaths, rushes for his gun and seeks out the disturber of his slumber. In case there be any unable to identify the koel, let it be said that the cock is black from head to foot, that he possesses a wicked-looking red eye, that he is about the size of a crow, but has a slighter body and a longer tail. The hen is speckled black and white. This bird spares not even Sind or the Punjab. It visits every part of the plains of India, wintering in the south and summering in the north.
The third of the triumvirate, the common Indian cuckoo (Cuculus micropterus), although in its way a very fine bird, is not of the same calibre as its confrères. It stands to them in much the same relation as Trinity College, Dublin, does to the Universities of Oxford and Cambridge. It has quite a pleasant note, which Indians represent asBoutotaka, but which is perhaps better rendered by the words “wherefore, therefore,” repeated with musical cadence. It does not call much during the middle of the day. It usually uplifts its voice about two hours before sunset, and continues until the sun has been up for a couple of hours. This cuckoo is very common in the Himalayas and in the plains of India from Fyzabad to Calcutta. Fyzabad ought really to be renamed Cuckooabad. It is the habitation of untold numbers of cuckoos. There during the merry month of May the cuckoos spendthe night chanting anthems of which the refrain runskui-il, ku-il, ku-il, wherefore, therefore, brain-fever, brain-fever, brain-fever. The Indian cuckoo is very like the English cuckoo in appearance, and it victimises the seven sisters (Crateropus canorus) and other babblers, as does the brain-fever bird.
The night-loving cuckoos have demanded so much space that the other vocalists of the hours of darkness will have to be content with very brief notice.
The night heron (Nycticoran griseus) makes the welkin ring with his guttural cries of “waak, waak,” uttered as he flies after nightfall from his roost to the pond where he will fish till morning. As he fishes in silence the addition he makes to the noises of the night is not great. The large family of plovers must be dismissed in a single sentence. They, like many cuckoos, regard sleep as a luxury; hence their plaintive cries are heard both by day and by night. The most familiar of their calls is the “did-he-do-it, pity-to-do-it,” of the red-wattled lapwing (Sarcogrammus indicus). The notes of the rest of his family consist of variations of the wordstiteri, titeri.
In conclusion, mention must be made of the nightjars or goatsuckers, as they are sometimes called after the fashion of the Romans, who believed that these birds used to sally forth at night and milk goats. This belief was based on two facts. First, the udders of goats were often found to be empty in the morning; secondly, the broad gape possessed by the nightjar. However, the character of these birds has now been cleared. We know that their bills are wide in orderto seize large insects on the wing, and that if goats yield no milk in the morning it is not the nightjar who is to blame. Nightjars are brownish grey birds, mottled and barred all over like cuckoos, for which they are often mistaken. Two are common in India. The first of these isCaprimulgus asiaticus, the common Indian nightjar, whose call is heard only after nightfall, and resembles the sound made by a stone skimming over ice. The other nightjar is that of Horsfield (Caprimulgus macrurus). Its note has been compared to the noise made by striking a plank with a hammer. The distribution of nightjars is capricious. They are fairly common in the western districts of the United Provinces.
Horsfield’s nightjar is abundant in thesalforests of the Pilibhit district.