However, the most striking effects of common life for the security of the individual, for its enjoyment of life, and for the development of its intellectual capacities, are seen in two great families of birds, the cranes and the parrots.  The cranes are extremely sociable and live in most excellent relations, not only with their congeners, but also with most aquatic birds.  Their prudence is really astonishing, so also their intelligence; they grasp the new conditions in a moment, and act accordingly.  Their sentries always keep watch around a flock which is feeding or resting, and the hunters know well how difficult it is to approach them.  If man has succeeded in surprising them, they will never return to the same place without having sent out one single scout first, and a party of scouts afterwards; and when the reconnoitring party returns and reports that there is no danger, a second group of scouts is sent out to verify the first report, before the whole band moves.  With kindred species the cranes contract real friendship; and in captivity there is no bird, save the also sociable and highly intelligent parrot, which enters into such real friendship with man.  “It sees in man, not a master, but a friend, and endeavours to manifest it,” Brehm concludes from a wide personal experience.  The crane is in continual activity from early in the morning till late in the night; but it gives a few hours only in the morning to the task of searching its food, chiefly vegetable.  All the remainder of the day is given to society life.  “It picks up small pieces of wood or small stones, throws them in the air and tries to catch them; it bends its neck, opens its wings, dances, jumps, runs about, and tries to manifest by all means its good disposition of mind, and always it remains graceful and beautiful."(21) As it lives in society it has almost no enemies, and though Brehm occasionally saw one of them captured by a crocodile, he wrote that except the crocodile he knew no enemies of the crane.  It eschews all of them by its proverbial prudence; and it attains, as a rule, a very old age.  No wonder that for the maintenance of the species the crane need not rear a numerous offspring; it usually hatches but two eggs.  As to its superior intelligence, it is sufficient to say that all observers are unanimous in recognizing that its intellectual capacities remind one very much of those of man.

The other extremely sociable bird, the parrot, stands, as known, at the very top of the whole feathered world for the development of its intelligence.  Brehm has so admirably summed up the manners of life of the parrot, that I cannot do better than translate the following sentence:—­

“Except in the pairing season, they live in very numerous societies or bands.  They choose a place in the forest to stay there, and thence they start every morning for their hunting expeditions.  The members of each band remain faithfully attached to each other, and they share in common good or bad luck.  All together they repair in the morning to a field, or to a garden, or to a tree, to feed upon fruits.  They post sentries to keep watch over the safety of the whole band, and are attentive to their warnings.  In case of danger, all take to flight, mutually supporting each other, and all simultaneously return to their resting-place.  In a word, they always live closely united.”