The eggs (see Fig. 35, Coloured Plate X.), from four to six in number, are laid about May, and are incubated entirely by the female. If the season is fine the male ministers to her wants, and the young are hatched in twelve days; but should the weather be cold or wet the unfortunate mother is expected to provide for herself, and must therefore leave her nest; if this is the case the nestlings do not quit the shell for about seventeen days. The young grow rapidly, and before they are fully fledged may be often seen peering and gaping above the sides of the nest, until able to accompany their parents during their daily excursions; yet, even then, they return to the nest for a short period as evening closes in. No sooner has the first family become self-supporting than the female again lays, but this time the eggs are fewer than before, and it is not uncommon for this second brood to be hatched so late in the season that the nestlings are too weak to accompany the rest of the family when the time for migrating arrives. A Spanish proverb says, "He who could destroy a Swallow could kill his own mother;" but, in spite of the reprobation of the act expressed in this popular adage, hundreds and thousands of these useful and sprightly birds are annually slaughtered out of mere wanton mischief, not only in that country, but in all parts of Europe, and yet few members of the feathered creation are more innocent, more useful, or more ornamental to the landscape. "The Swallow," says Sir Humphry Davy, "is one of my favourite birds, and a rival of the Nightingale, for he cheers my sense of seeing as much as the other does my sense of hearing. He is the glad prophet of the year, the harbinger of the best season; he lives a life of enjoyment, among the loveliest forms of Nature. Winter is unknown to him, and he leaves the green meadows of England in autumn, for the myrtle and orange groves of Italy, and for the palms of Africa. He has always objects of pursuit, and his success is secure. Even the beings selected for his prey are poetical, beautiful, and transient. The ephemeræ are saved by his means from a slow and lingering death in the evening, and killed in a moment when they have known nothing but pleasure. He is the constant destroyer of insects, the friend of man, and a sacred bird. His instinct, which gives him his appointed season, and teaches him when and where to move, may be regarded as flowing from a Divine source; and he belongs to the oracles of Nature, which speak the awful and intelligible fiats of a present Deity." [Illustration: THE THREAD-TAILED SWALLOW (_Cecropis-Uromitus-filifera_).]