The nest, made of dry grass lined with feathers, is placed at the extremity of the long, straight, cylindrical burrow, and contains five or six white pointed eggs. I have never seen these Swallows fighting with the Minera to obtain possession of the burrows, for this industrious little bird makes itself a fresh one every spring, so that there are always houses enough for the Swallows. After the young have flown, they sit huddled together on a weed or thistle-top, and the parents continue to feed them for many days. As in size and brightness of plumage, so in language is the Bank-Swallow inferior to other species, its only song being a single, weak, trilling note, much prolonged, which the bird repeats with great frequency when on the wing. Its voice has ever a mournful, monotonous sound, and even when it is greatly excited and alarmed, as at the approach of a fox or hawk, its notes are neither loud nor shrill. When flying they glide along close to the earth, and frequently alight on the ground to rest, which is contrary to the custom of other Swallows. Like other species of this family, they possess the habit of gliding to and fro before a traveller's horse, to catch the small twilight-moths driven up from the grass. A person riding on the pampas usually has a number of Swallows flying round him, and I have often thought that more than a hundred were before my horse at one time; but, from the rapidity of their motions, it is impossible to count them. I have frequently noticed individuals of the four most common species following me together; but after sunset, and when the other species have long forsaken the open grassy plain for the shelter of trees and houses, the diminutive Bank-Swallow continues to keep the traveller company. At such a time, as they glide about in the dusk of evening, conversing together in low tremulous tones, they have a peculiarly sorrowful appearance, seeming like homeless little wanderers over the great level plains. When the season of migration approaches they begin to congregate in parties not very large, though sometimes as many as one or two hundred individuals are seen together; these companies spend much of their time perched close together on weeds, low trees, fences, or other slightly elevated situations, and pay little heed to a person approaching, but seem preoccupied or preyed upon by some trouble that has no visible cause. The time immediately preceding the departure of the Swallows is indeed a season of very deep interest to the observer of nature. The birds in many cases seem to forget the attachment of the sexes and their songs and aerial recreations; they already begin to feel the premonitions of that marvellous instinct that urges them hence: not yet an irresistible impulse, it is a vague sense of disquiet; but its influence is manifest in their language and gestures, their wild manner of flight, and their listless intervals.