A few days elapse after the completion of the fabric, not usually more than two, in which mutual congratulations are passed. Then comes the drama in which the female is the principal actor--namely, the laying of the eggs. This requires four days, in ordinary instances, one egg being deposited daily. Incubation then succeeds, and lasts for eleven days. Here the female displays her true motherly instinct. She enters the nest, and with unwearied perseverance continues thereon, save during brief intervals of absence in quest of food, until she has achieved her heart's desire. The male is said to relieve her, but if such is the case, we have never been a witness of the fact. But while keeping aloof from such fatiguing duty, he is nevertheless a very faithful and devoted father when the young have quit their narrow prison-houses and welcomed the light of a new life. He is now as solicitous for their safety and well-being as the mother, and in case of molestation, unites his cries with hers to frighten away the intruder, or to cause him to desist from any assault he may have in contemplation. When twelve days old the little Swifts are able to climb to the summit of the chimney and receive their food. This always occurs a few days before their wings are sufficiently developed for flight. Even while quite young, in case of accident to the nest, they are able to make their way to the top of the chimney. In some cases they are carried beyond the reach or notice of their parents. When such occur they stubbornly refuse, human assistance, although uttering the most pitiful cries of hunger. When placed upon the roof contiguous to their native chimney, Dr. Brewer has known them to descend to its base, and there receive parental attention. In a fortnight they leave the nest, and are able to care for themselves. As this species is double-brooded in Pennsylvania the young are necessarily forced to self-maintenance at an early age, the thoughts of the parents being engrossed with preparations for a second family. These arrangements are perfected about the middle of June. In New England, and further north, but one brood is raised.
Like the old birds, the young are crepuscular rather than nocturnal in their habits, preferring to hunt for their prey early in the morning and late in the afternoon, or during cloudy weather. At times these predatory excursions occur at noonday in the broad glare of a full-orbed sun. The period for hunting is apparently regulated by the abundance or scarcity of appropriate insects. The adult birds, when with young, have often been known to protract their search for food long after night-fall. Caterpillars, diptera, beetles and lepidoptera of various kinds, constitute their _menu_, vast numbers of injurious, as well as beneficial species, being destroyed. Mature insects are chiefly in demand, which the birds, from being constantly on the wing, procure without much difficulty. Their flight then is varied and difficult of description. It consists of rapid sailing, and divers turnings, with occasional quickly repeated strokes of the wings. They never rest except in their roosting-places, to the walls of which they cling with great tenacity, being partially supported by their rigid tails. When tired of flight, they seek their homes, which they enter by falling headforemost, without any apparent concern. Their only note in these gastronomic explorations is a simple _chip_, uttered with considerable force, and at times so quickly, as to give rise to a confused twittering.
