Steeples, lofty edifices, and in some countries rocks, are the situations preferred by this species when about to build. The nest is constructed of hay, dry leaves, blades of grass, or even bits of rag, cemented into a solid mass by the saliva from the builder's beak. The two or at most three eggs that constitute a brood are white, elongate, and of the same breadth at both ends. The female begins to lay at the end of May; she alone performs the work of incubation, and is fed by her mate if the weather be fine; should it, however, be wet, she is compelled to leave her little family, and go herself in pursuit of insects, as the male can only provide for his own requirements. The young grow very slowly and remain for many weeks under parental care, indeed, they are rarely fully fledged until the end of August. It is by no means uncommon for these birds to avoid all the trouble attendant on nidification, by setting upon and worrying a Starling or Sparrow until they have compelled it to resign its little domicile; under these circumstances, if the eggs of the late occupier have been already laid, the marauder simply covers them with a layer of some elastic material, and on this the female deposits her brood. These Swifts subsist almost entirely on insects, and usually require a large supply of food; they can, however, occasionally fast for a lengthened period. THE ALPINE SWIFT. The ALPINE SWIFT (_Cypselus Melba_) is considerably larger and more powerful than the bird last described, its length being about eight, and its breadth from nineteen to twenty inches; the wing measures eight and the tail three inches. The plumage of this species is dusky greyish brown above, and white upon the throat and belly; the rings around the eyes are deep brown, and the feet and beak black. The young are recognisable by the light edge upon their feathers.