Sonnerat, in his "Voyage to India," speaks of a Cape Tit, the nest of which is in the form of a bottle, and composed of cotton. While the female hatches the eggs, the male, like a true sentinel, maintains a strict watch on a specially-formed resting-place, built on one of the sides. Finally, for ingenious construction, instigated by affection for its progeny, there is nothing to compare to the work of the Republican ([Fig. 79]). This little bird of the Cape, which is about the size of a Sparrow, which it much resembles, lives in numerous families, that unite in forming immense colonies. Their dwellings have the appearance of a circular framework surrounding the trunk of some large tree, as represented beneath. Levaillant counted as many as three hundred cells, which indicate that it is inhabited by six hundred birds. These nests are so heavy that Levaillant was compelled to employ a cart with many men in transporting one of their colonies. At a distance they resemble great roofs attached to the trunks or branches of trees, on which hundreds of birds sport and enjoy themselves. Further, the Oriole suspends its basket-like nest by a twig at the extremity of a flexible branch, placing it thus beyond the reach of any prowling four-footed ravisher. The Magpie selects the topmost fork of the loftiest trees. Again, the nest of the esculent Eastern Swallow, the one so much sought after by gourmands, hangs from those cliffs washed by the sea, and is constructed of a fucus, or marine plant, of the genus Gelidium, which gelatinous substance, cemented by the saliva of the bird, forms a sort of paste of most delicate flavour.
When this nest is built, and the walls properly cemented, and the home of the little brood prepared, the eggs are laid and the process of hatching commences. Eggs are generally numerous in inverse proportion to the size of the bird. The Eagle lays two, for instance, while the Titmouse (Parus) lays from twelve to eighteen.
The eggs laid, the female must now submit to the long and painful labour of incubation. While the male lies in wait in the neighbouring bush to defend his young brood against any enemy which may present itself, giving battle to much larger animals if they venture to attack his nest, the female only quits her charge for necessary food, and her place is often occupied during her absence by her mate. Enemies that lie in wait are numerous. Among them may be enumerated birds of prey, small quadrupeds, reptiles which treacherously insinuate themselves into the nest, and perhaps more unfeeling than all, children with destructive instincts.
If nothing occurs to disturb the repose of the pair, the male, perched upon a neighbouring branch, pours out a song expressive of his felicity. The little ones are finally hatched. Helpless and incapable, without feathers and with closed eyes, they are utterly dependent on the parent birds, by which they are fed until the time when they are covered with feathers. They now begin to try their wings, and find their own food. The mother directs their first efforts, uttering a peculiar cry to attract them when she discovers a favourite morsel; defending them courageously, and, with a total abnegation of self, meeting the most formidable enemies; sometimes going so far for their protection as to offer herself a victim. How pitiful are the cries of a Swallow whose nest is built under the roof of a house on fire! Fearlessly she rushes on the flames, flying to the assistance of her young, as if she would rescue them or perish under the fatal roof. Or mark the unhappy Partridge which the sportsman has surprised on the nest. She hesitates not to offer herself a sacrifice, throwing herself almost under the intruder's feet, in order to attract his attention from her progeny.
When the young are strong enough to take wing, they abandon the family tie, and soon lose themselves in the great world of nature, forgetful of their parents' unselfish care. The ingratitude of their first-born does not, however, discourage the forsaken couple. With the returning season they renew their labours, exhibit the same solicitude, the same affection, to meet with the same return. Nature is an unfailing source—an eternal focus of tenderness and love.
Most families of birds are migratory; that is, they abandon their summer quarters and undertake long journeys at certain seasons. These migrations occur with the greatest regularity. By their departure from temperate or cold climates they prognosticate the approach of winter, as their return heralds spring. Among the ancient Greeks, as we learn from a passage of Aristophanes on birds, the arrival of the Crane pointed out the time of sowing; the arrival of the Kite the sheep-shearing season; and the arrival of the Swallow in Greece was the date for putting off summer clothing. The impulse which causes birds to depart is an instinctive desire to find climatic conditions appropriate to their wants of life. At the approach of winter they desert the regions of the north in search of southern countries with a warmer climate, while others migrate northwards to escape the heat.
Nevertheless, all birds are not migratory; many species remain during their whole lives in the locality where they were hatched, straying but little distance from their birth-place. The majority of those which migrate perform their journeys annually and with great regularity; a few irregularly and accidentally; that is, they are caused by necessity, or by atmospheric influences, to change their residence; and it is no unusual sight on such occasions to see numerous flocks of birds assembling under the leadership of a chief, and taking their flight in perfect order, traversing seas, and passing from one continent to another, with astonishing rapidity. On the 22nd of September, 1771, White, of Selborne, witnessed the flight of a flock of Swallows which had rendezvoused the night before in a neighbour's walnut-tree. "At dawn of what was a very foggy day, they arose all together in infinite numbers, occasioning such a rustling from the strokes of their wings against the hazy atmosphere that the sound might be heard at a considerable distance." In the Old World, choosing a time when the winds are favourable, most migratory birds direct their flight towards the south-west in the autumn, and the north-east in spring. In America the migratory birds take a south-east direction in autumn, and the reverse in spring. These aërial travellers instinctively direct their flight to the same regions—often to the same district; and there are good grounds to believe that the same pair frequently find their way year after year to the same nest.
The duration of the life of birds in a state of nature is one of those subjects on which little is known. Some ancient authors—Hesiod and Pliny, for example—give to the Crow nine times the length of life allotted to man, and to the Raven three times that period; in other words, the Carrion Crow, according to these authors, attains to seven hundred and twenty years, and the Raven two hundred and forty. The Swan, on the same authority, lives two hundred years. This longevity is more than doubtful. Paroquets, however, are known to have reached more than a hundred. Goldfinches, Chaffinches, and Nightingales unquestionably, even in the confinement of a cage, have lived four-and-twenty years. A Heron, Girardin tells us, lived fifty-two years, which was testified by the ring which he bore on one of his legs, and even then he lost his life by an accident, while in full vigour. A couple of Storks, moreover, have been known to nestle in the same place for more than forty years. All that we can affirm is that birds live much longer than the Mammalia.
We can easily fix a circumscribed geographical boundary to any species of Mammalia. They may be limited to a country, or even a district. Can we impose a like distribution on birds? At first sight this seems difficult: their powerful organs of locomotion permit of their travelling rapidly; and, moreover, their nature, essentially mobile, and their wandering humour, lead them to continual change; and then their organisation adapts them for great extremes of temperature—circumstances which would lead us to consider them quite cosmopolite. Nevertheless, many species reside habitually in countries of very limited range. A Sovereign Hand has traced on the surface of the globe limits that cannot be passed. How such small creatures are able to perform such distant journeys, pausing only at far-severed resting-places for necessaries, has always been a matter of surprise. They pass on without an instant's sleep, however long and fatiguing the route. How can the Quail, for instance, with its short wing and plump body, traverse the Mediterranean twice in the year? Hasselquist tells us that small short-winged birds frequently came on board his ship in squally weather, all the way from the Channel to the Levant; and Prince Charles Bonaparte was agreeably surprised by the visit of a party of Swallows to the ship Delaware, in which he was a passenger, when five hundred miles from the coast of Portugal, and four hundred from Africa. Audubon relates a similar occurrence; and numerous instances are recorded in which these fatigued travellers have taken shelter in the first fisherman's boat they met, sometimes so weak as to be hardly able to move a wing. It is therefore a fact truly inexplicable, in spite of every hypothesis, more or less reasonable, which has been advanced by naturalists in explanation.
Men have little influence over birds, and have, therefore, few opportunities of studying their habits in a state of nature. Some few species may be retained in captivity, and some observers have been able to obtain their entire confidence while in that condition; but, except two or three species, it has not been possible to reduce them to a state of domestication. Our knowledge of the habits and manners of the feathered race is, therefore, entirely dependent on chance observation.