III.—The Instinctive Behaviour of Young Birds
Since it is easy to hatch birds of many species in an incubator, and to rear them under conditions which not only afford facilities for observation but exclude parental influence, their study has special advantages. One can with some approach to accuracy distinguish the instinctive from the acquired factors in their behaviour.[34]
Fig. 15.—Newly-hatched Chick swimming.
The callow young of such birds as pigeons, jays, and thrushes are hatched in a helpless condition, and require constant and assiduous ministration to their elementary organic needs. Most of their instincts are of the deferred type. But pheasants, plovers, moor-hens, domestic chicks, and ducklings, with many others, are active soon after birth, and exhibit powers of complex co-ordination, with little or no practice of the necessary limb-movements. They walk and balance the body so soon and so well as to show us that this mode of procedure is congenital, and has not to be gradually acquired through the guidance of experience. Young water-birds swim with neat and orderly strokes the very first time they are gently placed in water. Even little chicks a day or two old can swim well. Dr. Thorndike, who draws attention to this fact,[35] appears to accept the view, suggested by Dr. Bashford Dean, that the movements are not those of swimming but only of running. I have carefully watched the action through the glass walls of a tank and compared it with that of a young moor-hen. In the two cases it is quite similar in type, and the type appears to be different from that of running, though it is perhaps hard to distinguish the two. In any case, the hand over hand action is well co-ordinated, and is very different from a mere excited struggle. Chicks twenty-six hours old taken straight from the incubator drawer, before they had taken food, made directly for the side of the tank and tried to scramble out. They gradually sank deeper through the wetting of the down, but could keep afloat for from two to three minutes. I have made observations on chicks of various ages from twenty-four hours to a month, and find in all cases similar results; but with the older birds the flapping of the wings and more vigorous action cause them to get water-logged more rapidly. There is some apparent distress with cries; but less than one might expect under the circumstances. For the purposes of the above illustration Mr. Charles Whymper had before him a sketch I made of the leg-action, and instantaneous photographs of the chicks swimming for which I am indebted to my colleague Mr. George Brebner. I have not observed the behaviour of an adult hen when placed in the water. Dr. Thorndike says, “there is no vigorous instinct to strike out toward the shore,” she “will float about aimlessly for awhile and only very slowly reach the shore.” But Mrs. Foster Wood informs me that she has seen a hen leap into a pond after her brood of ducklings and swim to the other side, a distance of twenty feet.
Diving, in water-birds, is also an instinctive mode of behaviour; and this is obviously a more difficult procedure than swimming, one further removed from reflex action. And careful observations have placed beyond question the fact that flight is also instinctive. A swallow, for example, taken from the nest under conditions which made it practically certain that it had never yet taken wing, exhibited guided flight, and attempted to alight on a suitable ledge. Of course flight is generally a deferred instinct, and is not performed until the wings have reached a suitable state of development. An instinctive response, which may perhaps be regarded as one of its initial stages, is seen in quite young chicks. If placed in a basket, and rapidly lowered therein through a foot or two, the chick will extend its skinny and scarcely feathered wings. But though, from the usual conditions of development, flight in birds is a deferred instinct, yet in exceptional cases it may be connate. The mound-builders (Megapodes) of the Australian region are hatched from large eggs in warm earth or sand, and are not tended by the parents. So well fledged are these birds that they can fly the day they emerge from the egg. Dr. Worcester, while digging in one of their mounds, made an unsuccessful attempt to seize one which was newly hatched; but it flew several rods into thick brush, and this notwithstanding the fact that it had probably never before seen the light of day.
Fig. 16.—Nestling Megapode, to show the well-developed wings. (From Dr. R. Bowdler Sharpe’s “Wonders of the Bird World.”)
It must not be supposed that, in adducing flight as an example of instinctive behaviour in birds, we are contending that it is this and nothing more throughout life. The inference to be drawn from the facts of observation is rather that instinct provides a general ground plan of behaviour which intelligent acquisition, by enforcing here and checking there, perfects and guides to finer issues. Few would contend that the consummate skill evinced in fully developed flight at its best, the hurtling swoop of the falcon, the hovering of the kestrel, the wheeling of swifts in the summer air, the rapid dart and sudden poise of the humming bird, the easy sweep of the sea-gull, the downward glide of the stork—that these are, in all their exquisite perfection, instinctive. A rough but sufficient outline of action is hereditary; but the manifold graces and delicacies of perfected flight are due to intelligent skill begotten of practice and experience.
There are many little idiosyncracies and special traits of flight which are probably instinctive—such as enable an ornithologist or a sportsman to recognize a flying bird from a distance. And the same is true of other modes of behaviour. The observer of young birds cannot fail to note and to be impressed by many of these. The way in which a little moor-hen uses its wings in scrambling up any rough surface is very characteristic; so, too, is the manner in which a guinea-chick runs backwards and then sideways at a right angle when one attempts to catch him. If suddenly startled, moor-hens and chicks scatter and hide; plovers drop and crouch with their chins on the ground; pheasants stand motionless and silent. Knowledge of the ways of birds enables one to predict with tolerable accuracy how each kind will behave under given circumstances. That the actions are always precisely alike cannot be said with truth; but that the behaviour is so relatively definite as to be readily recognizable can be confidently asserted. That a moor-hen will flick its tail, that a chick will dust itself in the sand, that pheasants and partridges will scratch the ground, that a jay will go through certain actions in the bath, that the preening of the down will be carried out in particular ways—moor-hens, for example, wringing out the water in a peculiar manner,—and that all these, and many other modes of behaviour, will be presented in relatively definite ways: all these are, to borrow a phrase of Dr. Peckham’s, so characteristic of the several groups of birds, that they would be an important part of any definition based upon behaviour. And there can be no question that they are instinctive. They may indeed seem trivial and commonplace, scarcely worthy of special note; but they serve to show in how many details organic heredity lays the foundation for future behaviour, and affords groups of data for effective consciousness to utilize.
To show the instinctive nature of such behaviour, the following examples will suffice. One of a batch of moor-hen chicks showed once, and once only, when a week old, an incipient tendency to bathe in the shallow tin of water which was placed in their run, but soon desisted; nor was the action repeated, though he and the others enjoyed standing in the water. Five weeks later one of the batch was taken to a beck. He walked quietly through the comparatively still water near the edge; but when he reached the part of the stream where it ran swiftly and broke over the pebbles, he stopped, ducked, and took an elaborate bath, dipping his head well under, flicking the water over his back, ruffling his feathers, and behaving in a most characteristic manner. Each day thereafter he did the same, with a vigour that increased up to the third morning, and then remained constant. The same bird some weeks later was swimming in a narrow part of the stream, with steep banks on either side, when he was frightened by a rough-haired pup. Down he dived, for the first time in his life; and after a few seconds his head was seen to appear, just peeping above the water beneath the bank.
Ten days after receiving two nestling jays I placed in their cage a shallow tin of water. They took no notice of it, having never seen water before; for they were fed chiefly on sopped food. Presently one of them hopped into it, whether attracted by the water or by accident it is difficult to say, squatted in it bending his legs, and at once fluttered his feathers, as such birds do when they bathe, though his breast scarcely touched the water. The other seized the tin in his bill, and then pecked at the water, thus wetting his beak. He, too, fluttered his feathers in a similar fashion, though he was outside the tin and not in the water at all. A little later the first again entered the tin, and dipped his breast well into the water; this was followed by much fluttering and splashing. The bird took a good bath, as did the other shortly afterwards, and then spent half an hour in a thorough grooming, with much fluttering of the wings, the crest feathers being constantly raised and lowered, expressive of an emotional state.
Now, in these cases it would be impossible to say whether the behaviour was carried out in the manner characteristic of the species, prior to experience and independent of imitation, on the basis of mere casual and chance observation. But in these cases the whole life-history of the individuals concerned was known; and it can be asserted with confidence that the behaviour was hereditary, and not acquired by any gradual process of learning. Moreover, in each case there seemed to be such evidence as observation can afford, that internal emotional factors co-operated with the direct external stimuli in determining the nature of the behaviour. Whether such actions so far contribute to the well-being of the individual as to be of decisive advantage it is difficult to say. Some would contend that bathing is practised by birds merely for the pleasure it seemingly affords; others would urge that it is a means of getting rid of troublesome and presumably hurtful parasites, to the attacks of which birds are peculiarly subject.
Fig. 17.—Young Cuckoo ejecting nestling Meadow Pipit. (From Mrs. Hugh Blackburn’s sketch in “Birds from Moidart.”)
One of the most remarkable instincts of young birds is that of the cuckoo, which ejects eggs and nestlings from the home of its foster-parent. Mrs. Hugh Blackburn found a nest which contained two meadow-pipits’ eggs, besides that of a cuckoo. On a later visit “the pipits were found to be hatched, but not the cuckoo. At the next visit, which was after an interval of forty-eight hours, we found the young cuckoo alone in the nest, and both the young pipits lying down the bank, about ten inches from the margin of the nest, but quite lively after being warmed in the hand. They were replaced in the nest beside the cuckoo, which struggled about until it got its back under one of them, when it climbed backwards directly up the open side of the nest, and hitched the pipit from its back on to the edge. It then stood quite upright on its legs, which were straddled wide apart, with the claws firmly fixed halfway down the inside of the nest, among the interlacing fibres of which the nest was woven, and, stretching its wings apart and backwards, it elbowed the pipit fairly over the margin, so far that its struggles took it down the bank instead of back into the nest. As it was getting late, and the cuckoo did not immediately set to work on the other nestling, I replaced the ejected one and went home. On returning next day, both nestlings were found dead and cold, out of the nest.”[36] Here we have a definite account by an eye-witness, who sketched the young cuckoo, which was naked, blind, and could scarcely hold up its head. And her account, itself confirmatory of that given by Jenner in 1778, is confirmed by that of Dr. John Hancock,[37] who witnessed the ejection of a fledgling hedge-sparrow, which “was put over the edge of the nest exactly as illustrated by Mrs. Blackburn.” The procedure is unquestionably instinctive.
The sounds uttered by young birds are sufficiently definite to be readily recognized and are susceptible of classification. In domestic chicks at least six notes may be distinguished. First the gentle “peeping” note, expressive of contentment. A further low note, a double sound, seems to indicate extreme satisfaction and pleasure. Very characteristic and distinct is the danger-note—a sound difficult to describe, but readily recognized. If a humble-bee, a black-beetle, a big worm, a lump of sugar—anything strange and largish—be thrown to the chicks, this danger-note is at once heard; and it serves to place others on the alert, though this is perhaps the outcome of experience. Then there is the cheeping sound, expressive apparently of a state of mild dissatisfaction with the present state of affairs. It generally ceases when one throws some grain, or even stands near them. Extreme dissatisfaction is marked by a sharper, shriller squeak, when one seizes them against their inclination. Lastly, there is the shrill cry of greater distress, when, for example, their swimming powers are subjected to critical examination. With pheasants a gentle, “peeping” note of contentment, a shriller cry of distress, and a danger-note, generically like, but specifically distinct from, that of the chick, are early differentiated. The complaining note of the partridge is uttered six or seven times in quick succession, followed by a pause. The note of the plover is high-pitched, and much like the familiar cry of the adult bird, to which it owes its popular name of “peewit.” So, too, the guinea-fowl in down utters from the first notes quite characteristic of its kind, while its danger-note is not unlike that of the chick or pheasant. The piping of ducklings is comparatively monotonous, and there does not seem to be a definite danger-note. With moor-hen chicks, even on the first day, two notes are well-marked—a call-note, lower in pitch than that of the chick, and rather harsh and raucous, and a “tweet, tweet” of pleasure, something like the contented note of a canary. Later, five or six notes are differentiated, the most characteristic of which is the harsh “crek, crek,” when the little bird is from any cause excited. It is uttered in a crouching attitude, with head thrown back and wings held outwards and forwards, waving to and fro in a very characteristic manner. That this has suggestive value for other moor-hen chicks is shown by its distinctly infectious effect; if one bird has cause to utter the note and strike the attitude others follow suit. While clearly instinctive in their mode of occurrence, while they seem to show well the co-operation of an internal emotional factor, their biological value seems to lie in their suggestive effect on other members of the brood. They form an elementary but sufficient social bond.
If these notes afford evidence of an incipient social factor, the instinct of pecking is distinctively individualistic. Chicks peck with considerable but not complete accuracy of aim at practically anything of suitable size at suitable distance; but it is through experience that they learn what to select for food and what to reject or leave untouched. Moving objects, however, are more readily pecked at than those which are still; and the instinctive response seems to be stimulated if one tap on the ground near the object, or move it with a pencil, thus simulating the action of the hen. And this is even more marked with pheasants and partridges. Plovers seize small worms with an avidity which looks like an inherited response to the sight of natural food. Pheasants and partridges also appear to be specially affected by worms, and when one of them seizes a worm for the first time, he shakes it and dashes it against the ground. Chicks, a week or ten days old, also seize a largish fly or bee with a dash, and maul it on the ground, throwing it on one side before again approaching it. And such birds seem to show an instinctive tendency to bolt with such treasures as caterpillars or small worms. Moor-hens cannot at first be induced to take food from the ground. It has to be held above them, whereupon they crouch down, with head and neck held back, opening their beaks more like the callow young of nursling birds; but they also strike upwards at the object—these modes of behaviour being, no doubt, correlated with the manner in which the mother moor-hen normally feeds her young from her beak during the early days of life. Callow fledglings, such as young jays, simply open their mouths, gaping widely to be fed. And many will respond in this way to such a note as a low whistle, as may readily be seen with swallows. But at a later age such birds show instinctive modes of reaction of a more complex type. A jay, for example, was offered a summer chafer or June bug, seized it at once in his bill, and tried to place his foot on it. Then he hopped down on to the floor of his cage, dropped the beetle, seized it again as it crawled off, and after two or three attempts swallowed it, tossing it back from the point of his bill into the throat. This was the first time he took food from the ground or swallowed it in this manner.
On the whole, there seems to be much inherited definiteness of co-ordination, and some tendency to respond in a definite manner to specific stimuli. That there should not be more differentiation in this respect than observation discloses is probably due to the fact that the parent birds afford, under natural conditions, much guidance in the selection of food. Since the solitary wasp unerringly seizes its appropriate food, since it responds instinctively to specific stimuli, there would seem no reason why birds should not show similar instinctive differentiation. But one must remember that in the case of the wasp there is no parental guidance; the insect is more completely dependent on instinct than is the bird to whose needs the hen assiduously ministers.
It is at first sight surprising that such birds as chicks and pheasants do not peck instinctively at still water. When a shallow vessel containing water was placed among some little chicks, several of them ran repeatedly through the water, but took no heed of it. Then, after about an hour, one of them standing in the vessel pecked at his toes, and at once lifted his head and drank freely with characteristic action. Another subsequently pecked at a bubble near the edge, and then he too drank. In fact, the best way of inducing them to drink is to scatter some grains of food in the tin; they peck at the grains, which catch their eye, and incidentally find the water, and the touch of water in the bill at once leads to the characteristic response and congenitally definite behaviour. That the sight of a still surface does not itself suffice to evoke this behaviour is probably again due to the fact that under nature the hen guides them and pecks at the water, when they follow her lead.
One fact which must be constantly borne in mind is that what is inherited is instinctive co-ordination, often related to a definite stimulus, not instinctive knowledge. A chick pecks at a grain when it is at a suitable distance, not because instinct provides him with the knowledge that this is something to be seized and tested, but because he cannot help doing so. He is so organized that this stimulus produces that result through an organic co-ordination that is independent of conscious knowledge or experience. How definite is the inherited co-ordination is shown by many observations. A young pheasant, only a few hours old, was taken from the incubator drawer, and held snugly while a piece of egg-yolk was moved before his eyes with the aid of fine forceps. He did not peck at it, but followed with movements of his head every motion of the object in a narrow circle. Simple as this action seems, it presents a striking example of co-ordinated movements accurately related to movements in the visual field, the whole performed without any opportunity for learning or practice, and less than half an hour after the bird was taken from the drawer of the incubator and first saw daylight. Psychologists sometimes puzzle their heads over the question how and by what steps the field of vision and the field of movement are brought into relation with each other; but in such a case as this, the problem ceases to be primarily psychological. The relation is purely organic; the conscious data are grouped from the outset. With young jays there was no such co-ordination at first; and when they began after a few days (about twelve or fourteen) to follow an object with the head and eye, the movements were at first jerky. But a week later, when I swept the food through a circle a foot in diameter in front of their cage, it was followed smoothly and evenly. Here a certain amount of learning and practice, absent in the case of the pheasant, was required. And it is difficult to say what proportion of the final result was acquired, what proportion hereditary; but probably the behaviour is in the main instinctive, though somewhat deferred.
One more example, perhaps even more trivial in the eyes of some people, may be given. A duckling a few hours old will scratch the side of his head. It is true he may topple over in the process, through insufficient powers of balance, for the simultaneous performance of poising on one leg and having a good scratch with the other is no easy matter. But let not either our familiarity with such behaviour, nor some observed and laughable failure on the part of the duckling, blind us to the fact that this is a congenital activity, and one of no little complexity, indicating a definite organic nexus. A local irritation sets agoing movements of the hind limb of that side through which just that particular spot is scratched in the absence of any previous practice, any learning to localize the spot. There can be no question that such inherited co-ordinations, whether perfect from the first, or with deferred perfection and some aid from acquisition, afford ready-made data to consciousness, which are of the utmost service in the guidance of subsequent behaviour. The two-days-old chick, with the aid of this instinctive co-ordination, performs well a number of actions, which, had she to consciously learn them all, would probably be still but half mastered when she was a skinny old hen.
Our whole treatment of instinctive behaviour has been based on the assumption, already to some extent justified, that experience is not inherited. If it be hereditary, how comes it that chicks show no recognition of still water, which must have been familiar to the experience of generation after generation of birds? How comes it that they do not even seem to recognize their natural parent and protector, the hen? Two chicks ten days old were taken to the yard whence were derived the eggs from which they were hatched, and were placed about two yards from a hen which was clucking to her brood. They were not in a frightened condition, for they stood on my hand and ate grain from it, scratching at the palm. But of the clucking of the hen they took no notice whatever. The same results were obtained with other chicks thirteen days old. Was this due, as Spalding suggested, to loss of the instinctive response which was perhaps present at an earlier age? Seemingly not. For a chick was taken at the age of two and a half days to its own mother, which had three chicks. These followed her about, and ran at once to her when she clucked and pecked on the ground. The little stranger, however, took no notice, nor did he show any tendency either to go to the hen or to follow the three chicks, having been purposely brought up alone. When the hen took her little brood under her wing, the stranger was placed close to her. She clucked, and seemed anxious to entice and welcome the little fellow, seizing an oat-husk and dropping it before him; but he remained indifferent, walking away and standing in the sunshine. After about forty minutes he seemed more inclined to go with the other chicks, but still ignored the existence of the hen. The natural instinctive tendency seems to be from the first to nestle under anything; and there is the hen provided by nature for the purpose. By experience the chicks grow accustomed to her fussy ways, as they grow accustomed to the ways of such a foster-parent as the writer of these pages. Still, though there is, apparently, no instinctive knowledge of the hen as their natural protector, and though I have seen no observable response to the clucking sound, this must not be taken as necessarily implying that there is no instinctive response to any of her modes of behaviour. There is such a response to her pecking on the ground; there is probably such a response to her danger-note; and there may be many other such instinctive modes of behaviour related to her actions. How far they extend can only be ascertained by patient observation; and such responsive behaviour need not imply any instinctive knowledge begotten of inherited experience.
We may now summarize some of the general conclusions which may be drawn from observations of instinctive behaviour in young birds.
1. That which is inherited is essentially a motor response or train of such responses. Mr. Herbert Spencer’s description of instinct as compound reflex action is thus justified.
2. These often show very accurate and nicely-adjusted hereditary co-ordinations.
3. They are evoked by stimuli, the general type of which is fairly definite, and may in some cases be in response to particular objects.
4. They are also generally shown under conditions which lead us to infer the presence of an internal factor, emotional or other.
5. There does not seem to be any evidence of inherited knowledge or experience.