As soon as spring comes back to the temperate zone, myriads and myriads of birds which are scattered over the warmer regions of the South come together in numberless bands, and, full of vigour and joy, hasten northwards to rear their offspring. Each of our hedges, each grove, each ocean cliff, and each of the lakes and ponds with which Northern America, Northern Europe, and Northern Asia are dotted tell us at that time of the year the tale of what mutual aid means for the birds; what force, energy, and protection it confers to every living being, however feeble and defenceless it otherwise might be. Take, for instance, one of the numberless lakes of the Russian and Siberian Steppes. Its shores are peopled with myriads of aquatic birds, belonging to at least a score of different species, all living in perfect peace—all protecting one another.
"For several hundred yards from the shore the air is filled with gulls and terns, as with snow-flakes on a winter day. Thousands of plovers and sand-coursers run over the beach, searching their food, whistling, and simply enjoying life. Further on, on almost each wave, a duck is rocking, while higher up you notice the flocks of the Casarki ducks. Exuberant life swarms everywhere."(1)
And here are the robbers—the strongest, the most cunning ones, those "ideally organized for robbery." And you hear their hungry, angry, dismal cries as for hours in succession they watch the opportunity of snatching from this mass of living beings one single unprotected individual. But as soon as they approach, their presence is signalled by dozens of voluntary sentries, and hundreds of gulls and terns set to chase the robber. Maddened by hunger, the robber soon abandons his usual precautions: he suddenly dashes into the living mass; but, attacked from all sides, he again is compelled to retreat. From sheer despair he falls upon the wild ducks; but the intelligent, social birds rapidly gather in a flock and fly away if the robber is an erne; they plunge into the lake if it is a falcon; or they raise a cloud of water-dust and bewilder the assailant if it is a kite.(2) And while life continues to swarm on the lake, the robber flies away with cries of anger, and looks out for carrion, or for a young bird or a field-mouse not yet used to obey in time the warnings of its comrades. In the face of an exuberant life, the ideally-armed robber must be satisfied with the off-fall of that life.
Further north, in the Arctic archipelagoes,
"you may sail along the coast for many miles and see all the ledges, all the cliffs and corners of the mountain-sides, up to a height of from two to five hundred feet, literally covered with sea-birds, whose white breasts show against the dark rocks as if the rocks were closely sprinkled with chalk specks. The air, near and far, is, so to say, full with fowls."(3)
Each of such "bird-mountains" is a living illustration of mutual aid, as well as of the infinite variety of characters, individual and specific, resulting from social life. The oyster-catcher is renowned for its readiness to attack the birds of prey. The barge is known for its watchfulness, and it easily becomes the leader of more placid birds. The turnstone, when surrounded by comrades belonging to more energetic species, is a rather timorous bird; but it undertakes to keep watch for the security of the commonwealth when surrounded by smaller birds. Here you have the dominative swans; there, the extremely sociable kittiwake-gulls, among whom quarrels are rare and short; the prepossessing polar guillemots, which continually caress each other; the egoist she-goose, who has repudiated the orphans of a killed comrade; and, by her side, another female who adopts any one's orphans, and now paddles surrounded by fifty or sixty youngsters, whom she conducts and cares for as if they all were her own breed. Side by side with the penguins, which steal one another's eggs, you have the dotterels, whose family relations are so "charming and touching" that even passionate hunters recoil from shooting a female surrounded by her young ones; or the eider-ducks, among which (like the velvet-ducks, or the coroyas of the Savannahs) several females hatch together in the same nest, or the lums, which sit in turn upon a common covey. Nature is variety itself, offering all possible varieties of characters, from the basest to the highest: and that is why she cannot be depicted by any sweeping assertion. Still less can she be judged from the moralist's point of view, because the views of the moralist are themselves a result—mostly unconscious—of the observation of Nature.
Coming together at nesting-time is so common with most birds that more examples are scarcely needed. Our trees are crowned with groups of crows' nests; our hedges are full of nests of smaller birds; our farmhouses give shelter to colonies of swallows; our old towers are the refuge of hundreds of nocturnal birds; and pages might be filled with the most charming descriptions of the peace and harmony which prevail in almost all these nesting associations. As to the protection derived by the weakest birds from their unions, it is evident. That excellent observer, Dr. Coues, saw, for instance, the little cliff-swallows nesting in the immediate neighbourhood of the prairie falcon (Falco polyargus). The falcon had its nest on the top of one of the minarets of clay which are so common in the canons of Colorado, while a colony of swallows nested just beneath. The little peaceful birds had no fear of their rapacious neighbour; they never let it approach to their colony. They immediately surrounded it and chased it, so that it had to make off at once.(4)
Life in societies does not cease when the nesting period is over; it begins then in a new form. The young broods gather in societies of youngsters, generally including several species. Social life is practised at that time chiefly for its own sake—partly for security, but chiefly for the pleasures derived from it. So we see in our forests the societies formed by the young nuthatchers (Sitta caesia), together with tit-mouses, chaffinches, wrens, tree-creepers, or some wood-peckers.(5) In Spain the swallow is met with in company with kestrels, fly-catchers, and even pigeons. In the Far West of America the young horned larks live in large societies, together with another lark (Sprague's), the skylark, the Savannah sparrow, and several species of buntings and longspurs.(6) In fact, it would be much easier to describe the species which live isolated than to simply name those species which join the autumnal societies of young birds—not for hunting or nesting purposes, but simply to enjoy life in society and to spend their time in plays and sports, after having given a few hours every day to find their daily food.
And, finally, we have that immense display of mutual aid among birds-their migrations—which I dare not even enter upon in this place. Sufficient to say that birds which have lived for months in small bands scattered over a wide territory gather in thousands; they come together at a given place, for several days in succession, before they start, and they evidently discuss the particulars of the journey. Some species will indulge every afternoon in flights preparatory to the long passage. All wait for their tardy congeners, and finally they start in a certain well chosen direction—a fruit of accumulated collective experience—the strongest flying at the head of the band, and relieving one another in that difficult task. They cross the seas in large bands consisting of both big and small birds, and when they return next spring they repair to the same spot, and, in most cases, each of them takes possession of the very same nest which it had built or repaired the previous year.(7)
This subject is so vast, and yet so imperfectly studied; it offers so many striking illustrations of mutual-aid habits, subsidiary to the main fact of migration—each of which would, however, require a special study—that I must refrain from entering here into more details. I can only cursorily refer to the numerous and animated gatherings of birds which take place, always on the same spot, before they begin their long journeys north or south, as also those which one sees in the north, after the birds have arrived at their breeding-places on the Yenisei or in the northern counties of England. For many days in succession—sometimes one month—they will come together every morning for one hour, before flying in search of food—perhaps discussing the spot where they are going to build their nests.(8) And if, during the migration, their columns are overtaken by a storm, birds of the most different species will be brought together by common misfortune. The birds which are not exactly migratory, but slowly move northwards and southwards with the seasons, also perform these peregrinations in flocks. So far from migrating isolately, in order to secure for each separate individual the advantages of better food or shelter which are to be found in another district—they always wait for each other, and gather in flocks, before they move north or south, in accordance with the season.(9)