inhabitants differed only about one or two degrees from the ordinary standard in England*. At very high temperatures, however, there is a somewhat greater difference, as appears from the ingenious experiments made by MM. Delaroche and Berger, who exposed themselves to a heat of 228°, or sixteen degrees above that of boiling water: they ascertained that at such very high temperatures there is an increase of seven or eight degrees of the centigrade thermometert. The increase of cold on the contrary does not appear to influence the temperature of the body in a similar way; and hence we discover the cause why great cold proves less injurious and fatal to animals than might be reasonably anticipated. White of Selborne, speaking of gipsies, says: "These sturdy savages seem to pride themselves in braving the severity of the winter, and in living in the open air (sub dio) the whole year round. Last September was as wet a month as ever was known; and yet during those deluges did a young gipsy girl lie in the midst of one of our hop-gardens on the cold ground, with nothing over her but a piece of a blanket extended on a few hazel rods bent hoop-fashion and stuck in the earth at each end, in circumstances too trying for a cow in the same condition: within this garden there was a large hop-kiln, into the chambers of which she might have retired, had she thought shelter an object worthy her attention." Some half-wild cats (Felis domestica), which frequented a solitary farm-house on the borders of a wood, were more attentive to their comforts than this young gipsy; since a neighbouring kiln for drying corn was their favourite resort during winter when the fire was lighted§.

The law by which animal temperature is thus maintained at nearly the same degree on exposure to con* Phil. Trans. for 1814, p. 600. Journ. de Physique, lxxi. 289. Nat. Hist. of Selborne, lett. 67.

§ J.R.

siderable heat or cold, though it is not easy to reconcile it to any of the received theories, supplies the only known reason why some of the smaller and seemingly tender animals outlive the rigours of our severest winters. The magpie (Pica caudata, RAY), though rather a hardy bird, has been found having recourse to what is often practised by smaller birds-several of them huddling together during the night, to keep each other warm. A gentleman of intelligence and veracity informed us that he once saw a number of these birds (probably a young family with their parents) on a tree, in a fir plantation, sitting so closely together that they all seemed to be rolled up into a single ball. Little is known of the roosting of these birds; but among smaller species the habit in question is not uncommon. Even during the day, in severe winter weather, we have observed a similar practice in the house-sparrow (Passer domesticus, RAY). On a chimney top, which can be seen from our study window, we have often remarked the whole of a neighbouring colony of sparrows contest by the hour the warmest spot on the projecting brick ledge, which happened to be in the middle. Here the sun shone strongest, the kitchen fire below sent hither its most powerful influence, and here the fortunate occupant was best sheltered from the frosty wind which swept by its companions that had been jostled to the two extremities of the row. But none remained long in quiet, for as soon as the cold air pinched them on the exposed side, they removed to the middle, scolding and cackling most vociferously; and as those who held the best places refused to give them up, the new-comers got upon their backs and insinuated themselves between two of their obstinate companions, wedge fashion, as you thrust a book into a crowded shelf. The middle places were thus successively contested, till hunger drove the whole colony to decamp in search of food.

60

GROUND

CHAPTER IV.

BUILDERS.-THE

VIRGINIAN RAIL.

THE GREBE. THE AMERICAN STILT. SWANS. THE EIDER-DUCK. THE SUMMER-DUCK. VARIATIONS FROM COMMON HABITS IN BUILDING. THE REDBREAST.

THE essential requisites of a bird's nest are warmth and security—a certain degree of heat being indispensable for hatching the eggs and fostering the young, while security from enemies and accidents is no less necessary for successfully rearing the brood. The various means resorted to for fulfilling these conditions afford numerous and interesting illustrations of this delightful part of natural history, and have given rise to much curious discussion among those philosophers who severally ascribe the building operations of birds to foresight and reason; to what is termed instinct, meaning mechanism without intelligence in the agent; or to immediate impulses from the great creative mind of the universe. Without entering, at least for the present, into the intricacies of these discussions, we shall enumerate a series of facts from which inferences may be drawn by the advocates of the various systems which attempt to explain the more mysterious operations of the lower animals.

Though the ground is proverbially termed "cold," it requires but slight observation to prove that the popular notion is not strictly correct, and consequently that the great number of birds which select

vantage of every variety of shelter. They are most commonly seen, indeed, creeping under the eaves of houses or the cornices of pillars; but they are equally fond of a hole in a hay-stack, of getting under the lee side of a rook's nest on a lofty tree, or of popping into a sand hole burrowed out for its nest by the bank swallow (Hirundo riparia, RAY). They are exceedingly partial, on this account, to the shelter of ivy on a wall, or of a thick tuft of clematis; but when they can find such a shelter, they do not, so far as we have observed, huddle together side by side, each individual merely selecting the warmest coping of leaves he can discover*.

It is not a little remarkable that the thrush and blackbird, though so careful to provide shelter and warmth for their eggs and young, show no wisdom in procuring the same comforts for themselves during winter, as they usually roost along with redwings and chaffinches in the open hedges, where they are often frozen to death in severe weather, or captured by bat fowlers. The starling (Sturnus vulgaris) exhibits more care for itself, by roosting in the holes of trees, in the towers of churches, or under the tiles of an old house, like the sparrows, and frequently among the thick tops of reeds in marshes. Yet will they sometimes suffer from frost even there. One winter's day in 1822, after a very keen frost in the night, when we were searching for lichens on the trees in Copenhagen-fields, we found a cock starling in a hole frozen to death. It was in very fine condition, and more perfect in plumage than we ever saw this species: but it did not appear, upon the closest examination, to have received any shot or other injury, to cause its death besides the effects of the frost.

It may be remarked, that like the sparrows and White's Selborne, letter 105.

* J. R..

G

gloomy weather, and at other times leave them altogether to the influence of the sunshine*.

In by far the greater number of instances, dryness seems to be a no less indispensable condition than warmth. But some birds are known to make use of moist rather than dry materials for their nests. This is well exemplified in a bird peculiar to America, called by Wilson the willet (Totanus semipalmatus, LATH.), from its reiterated shrill cry of Pill-will-willet, Pill-will-willet, which is loud enough to be heard at the distance of half a mile. This bird is very similar to the snipes, but may readily be distinguished from them by short webs at the joinings of the toes. The willets generally begin to lay about the twentieth of May, which is said, from some unknown cause, to be two weeks later than it was

twenty years ago. "Their nests," says Wilson,

66

are built on the ground, among the grass of the salt marshes, pretty well towards the land or cultivated fields, and are composed of wet rushes and coarse grass, forming a slight hollow or cavity in a tussock. This nest is gradually increased during the period of laying and sitting, to the height of five or six inches. The eggs are usually four in number, very thick at the great end and tapering to a narrower point at the other than those of our barn-door fowls. In every instance which has come under my observation, they are placed during incubation in an almost upright position, with the large end uppermost; and this appears to be the common practice of several other species of birds that breed in these marshes t."

It is not uncommon, among many other orders of the animal creation, to deposit eggs in a moist place,

* Vaillant, Oiseaux d'Afrique, Autruche; and Wilson, Amer. Ornith. vii. 81, &c.

Wilson, Amer, Ornith, vii, 28.