The sand-martin, although common enough in some localities, and found throughout the British Islands, including the Outer Hebrides and the Orkneys, is not a very well-known bird; for, however populous the country may be, and though other hirundines become increasingly domestic and breed under eaves, in porches, barns, and chimneys, he always preserves his original wild character. He is a swallow that is a stranger to man, and breeds in holes and crevices in precipitous cliffs on the sea-coast. But he prefers to excavate a breeding-hole in a perpendicular bank of clay not too stiff for his weak mining implements. Earth-cliffs on the banks of rivers and lakes and on the sea, are resorted to for this purpose, and he also takes advantage of the steep sides of railway-cuttings and sand and gravel pits. A suitable bank or cliff will often attract a large number of sand-martins, and the surface will appear riddled with their holes. It has always caused surprise in those who have observed this bird that it should be able with its small, weak bill to form such deep tunnels in the hard earth. The hole once made is, however, often used by the same birds for several years. They do not work by digging into the earth with their bills as a man digs with a knife or other implement. They perch against the surface and pick out small particles, and by means of this slow, laborious process accomplish their great work. The hole slants upwards, and is from three to four feet in length and two or three inches in diameter. At its extremity the gallery is widened to form a chamber about six inches in diameter, where the bed is made of dry grass, with a few feathers for lining. Male and female take turns in boring, working only in the morning, the rest of the daylight hours being spent in feeding and play. It sometimes happens that in boring their hole a sunken boulder or vein of impenetrable earth is met with; the hole is then abandoned and a new one begun in another place. By the end of May the eggs are laid. These are four to six in number, and are pure white. When hovering before their holes, and passing to and fro with wavering flight along the face of the bank, the sand-martins have a curious moth-like appearance. While flying about in company they constantly utter a low monotonous note; and this sound is prolonged to a scream when the birds are excited by the presence of some enemy. The male has, besides, a twittering song, uttered on the wing while hovering before the nesting-hole. Two broods are reared, and as soon as breeding is over the birds forsake the bank and scatter about the country, and may then be seen associating with house-martins and swallows. The sand-martin is the earliest of the swallows to arrive in this country, and the first to depart; it is rare to meet with them after the middle of September. Tree-Creeper. Certhia familiaris.