§ 5

Sight and hearing are highly developed in birds, and the senses, besides pulling the triggers of inborn efficiencies, supply the raw materials for intelligence. There is some truth, though not the whole truth, in the old philosophical dictum, that there is nothing in the intellect which was not previously in the senses. Many people have admired the certainty and alacrity with which gulls pick up a fragment of biscuit from the white wake of a steamer, and the incident is characteristic. In their power of rapidly altering the focus of the eye, birds are unsurpassed.

To the sense of sight in birds, the sense of hearing comes a good second. A twig breaks under our feet, and out sounds the danger-call of the bird we were trying to watch. Many young birds, like partridges, respond when two or three hours old to the anxious warning note of the parents, and squat motionless on the ground, though other sounds, such as the excited clucking of a foster-mother hen, leave them indifferent. They do not know what they are doing when they squat; they are obeying the living hand of the past which is within them. Their behaviour is instinctive. But the present point is the discriminating quality of the sense of hearing; and that is corroborated by the singing of birds. It is emotional art, expressing feelings in the medium of sound. On the part of the females, who are supposed to listen, it betokens a cultivated ear.

As to the other senses, touch is not highly developed except about the bill, where it reaches a climax in birds like the wood-cock, which probe for unseen earthworms in the soft soil. Taste seems to be poorly developed, for most birds bolt their food, but there is sometimes an emphatic rejection of unpalatable things, like toads and caterpillars. Of smell in birds little is known, but it has been proved to be present in certain cases, e.g. in some nocturnal birds of prey. It seems certain that it is by sight, not by smell, that the eagles gather to the carcass; but perhaps there is more smell in birds than they are usually credited with. One would like to experiment with the oil from the preen gland of birds to see whether the scent of this does not help in the recognition of kin by kin at night or amid the darkness of the forest. There may be other senses in birds, such as a sense of temperature and a sense of balance; but no success has attended the attempts made to demonstrate a magnetic sense, which has been impatiently postulated by students of bird migration in order to "explain" how the birds find their way. The big fact is that in birds there are two widely open gateways of knowledge, the sense of sight and the sense of hearing.

Instinctive Aptitudes

Many a young water-bird, such as a coot, swims right away when it is tumbled into water for the first time. So chicks peck without any learning or teaching, very young ducklings catch small moths that flit by, and young plovers lie low when the danger-signal sounds. But birds seem strangely limited as regards many of these instinctive capacities—limited when compared with the "little-brained" ants and bees, which have from the first such a rich repertory of ready-made cleverness. The limitation in birds is of great interest, for it means that intelligence is coming to its own and is going to take up the reins at many corners of the daily round. Professor Lloyd Morgan observed that his chickens incubated in the laboratory had no instinctive awareness of the significance of their mother's cluck when she was brought outside the door. Although thirsty and willing to drink from a moistened finger-tip, they did not instinctively recognize water, even when they walked through a saucerful. Only when they happened to peck their toes as they stood in the water did they appreciate water as the stuff they wanted, and raise their bills up to the sky. Once or twice they actually stuffed their crops with "worms" of red worsted!

Instinctive aptitudes, then, the young birds have, but these are more limited than in ants, bees, and wasps; and the reason is to be found in the fact that the brain is now evolving on the tack of what Sir Ray Lankester has called "educability." Young birds learn with prodigious rapidity; the emancipation of the mind from the tyranny of hereditary obligations has begun. Young birds make mistakes, like the red worsted mistake, but they do not make the same mistakes often. They are able to profit by experience in a very rapid way. We do not mean that creatures of the little-brain type, like ants, bees, and wasps, are unable to profit by experience or are without intelligence. There are no such hard-and-fast lines. We mean that in the ordinary life of insects the enregistered instinctive capacities are on the whole sufficient for the occasion, and that intelligent educability is very slightly developed. Nor do we mean that birds are quite emancipated from the tyranny of engrained instinctive obligations, and can always "ring up" intelligence in a way that is impossible for the stereotyped bee. The sight of a pigeon brooding on an empty nest, while her two eggs lie disregarded only a couple of inches away, is enough to show that along certain lines birds may find it impossible to get free from the trammels of instinct. The peculiar interest of birds is that they have many instincts and yet a notable power of learning intelligently.

Intelligence co-operating with Instinct

Professor Lloyd Morgan was foster-parent to two moorhens which grew up in isolation from their kindred. They swam instinctively, but they would not dive, neither in a large bath nor in a current. But it happened one day when one of these moorhens was swimming in a pool on a Yorkshire stream, that a puppy came barking down the bank and made an awkward feint towards the young bird. In a moment the moorhen dived, disappeared from view, and soon partially reappeared, his head just peeping above the water beneath the overhanging bank. This was the first time the bird had dived, and the performance was absolutely true to type.

There can be little doubt as to the meaning of this observation. The moorhen has an hereditary or instinctive capacity for swimming and diving, but the latter is not so easily called into activity as the former. The particular moorhen in question had enjoyed about two months of swimming experience, which probably counted for something, but in the course of that experience nothing had pulled the trigger of the diving capacity. On an eventful day the young moorhen saw and heard the dog; it was emotionally excited; it probably did to some extent intelligently appreciate a novel and meaningful situation. Intelligence cooperated with instinct, and the bird dived appropriately.

Birds have inborn predispositions to certain effective ways of pecking, scratching, swimming, diving, flying, crouching, lying low, nest-building, and so on; but they are marked off from the much more purely instinctive ants and bees by the extent to which individual "nurture" seems to mingle with the inherited "nature." The two together result in the fine product which we call the bird's behaviour. After Lloyd Morgan's chicks had tried a few conspicuous and unpalatable caterpillars, they had no use for any more. They learned in their early days with prodigious rapidity, illustrating the deep difference between the "big-brain" type, relatively poor in its endowment of instinctive capacities, but eminently "educable," and the "little-brain" type, say, of ants and bees, richly endowed with instinctive capacities, but very far from being quick or glad to learn. We owe it to Sir Ray Lankester to have made it clear that these two types of brain are, as it were, on different tacks of evolution, and should not be directly pitted against one another. The "little-brain" type makes for a climax in the ant, where instinctive behaviour reaches a high degree of perfection; the "big-brain" type reaches its climax in horse and dog, in elephant and monkey. The particular interest that attaches to the behaviour of birds is in the combination of a good deal of instinct with a great deal of intelligent learning. This is well illustrated when birds make a nest out of new materials or in some quite novel situation. It is clearly seen when birds turn to some new kind of food, like the Kea parrot, which attacks the sheep in New Zealand.

Some young woodpeckers are quite clever in opening fir cones to get at the seeds, and this might be hastily referred to a well-defined hereditary capacity. But the facts are that the parents bring their young ones first the seeds themselves, then partly opened cones, and then intact ones. There is an educative process, and so it is in scores of cases.

Using their Wits

When the Greek eagle lifts the Greek tortoise in its talons, and lets it fall from a height so that the strong carapace is broken and the flesh exposed, it is making intelligent use of an expedient. Whether it discovered the expedient by experimenting, as is possible, or by chance, as is more likely, it uses it intelligently. In the same way herring-gulls lift sea-urchins and clams in their bills, and let them fall on the rocks so that the shells are broken. In the same way rooks deal with freshwater mussels.

The Thrush's Anvil

A very instructive case is the behaviour of the song-thrush when it takes a wood-snail in its beak and hammers it against a stone, its so-called anvil. To a young thrush, which she had brought up by hand, Miss Frances Pitt offered some wood-snails, but it took no interest in them until one put out its head and began to move about. The bird then pecked at the snail's horns, but was evidently puzzled when the creature retreated within the shelter of the shell. This happened over and over again, the thrush's inquisitive interest increasing day by day. It pecked at the shell and even picked it up by the lip, but no real progress was made till the sixth day, when the thrush seized the snail and beat it on the ground as it would a big worm. On the same day it picked up a shell and knocked it repeatedly against a stone, trying first one snail and then another. After fifteen minutes' hard work, the thrush managed to break one, and after that it was all easy. A certain predisposition to beat things on the ground was doubtless present, but the experiment showed that the use of an anvil could be arrived at by an untutored bird. After prolonged trying it found out how to deal with a difficult situation. It may be said that in more natural conditions this might be picked up by imitation, but while this is quite possible, it is useful to notice that experiments with animals lead us to doubt whether imitation counts for nearly so much as used to be believed.