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sharp, and strong claws, worked by powerful muscles, recall the similar structure of these parts in the mole.
We must not take up further space by enumerating the burrowing powers of other edentata, such as the great armadillo, the manis, and other scaly-clad animals of North-America and India; but will conclude this short sketch of burrowing mammalia with a notice of another edentate animal, the aard-vark of South Africa. Mr. Wood gives us the following succinct
"The curious aard-vark of Southern Africa (Orycteropus Capensis) resides for the most part in great holes which it scoops in the ground. The name aard-vark is Dutch, signifying earth-hog, and is given to the animal on account of its extraordinary powers of excavation, and the swine-like contour of its head. The claws with which this animal works are enormous, as indeed is needful for the task which they are intended to perform. They are by no means intended merely to excavate burrows in soft or sandy soil, though they are frequently employed for that purpose; but they are designed for labours far more arduous. By means of these implements the aard-vark tears to pieces the enormous ant-hills which stud the plains of Southern Africa— edifices so strongly made as to resemble stone rather than mud, and capable of bearing the weight of many men on their summits. These marvellous dwellings are absolutely swarming with inmates; and it is for the purpose of feeding upon the tiny builders that the aard-vark plies its destructive labours. Towards evening the aard-vark issues from the burrow wherein it has lain asleep during the day, proceeds to the plains, and searches for an ant-hill in full operation. With its powerful claws it tears a hole in the side of the hill, breaking up the stony walls with perfect ease, and scattering dismay among the inmates. As the ants run hither and thither in consternation, their dwelling falling like a city shaken by an earthquake, the author of all this misery flings its slimy tongue among them, and sweeps them into its mouth by hundreds. . . . . Thus the aard-vark tears to pieces many a goodly edifice, and depopulates many a swarming colony, leaving a mere shell of irregular stony wall in the place of the complicated and marvellous structure which had sheltered so vast a population.'
Passing on now from burrowing mammalia, we come to burrowing birds; and these may be divided into those that excavate their own homes in earth or wood, and those which generally appropriate already-made hollows or tunnels, accommodating them to their respective habits. Of the true miners may be enumerated the sand-martin, the puffin, the woodpeckers, and the stormy-petrel of our own country. We shall restrict our notices to this latter division.
Amongst the swallow tribe we have an exceedingly interesting Vol. 120.-No. 240.
example in the pretty little sand-martin (Cotyle riparia), one of our earliest spring visitors, whose circular excavations are familiar to every one. In the cases of architecture hitherto noticed we have seen how obviously suited to these purposes are the implements of the animals employed. The strong palmated feet of the mole, with their five sharp-pronged nails, bespeak the animal's occupation at a glance; but this palpable adaptability of the instrument to the work which it performs is far from being always recognisable in several animals.
Among birds, the little sand-martin, with its slender feet and minute bill, seems at first sight but ill-fitted for engineering operations. Few would suppose,' as Mr. Wood remarks, ‘after contemplating its tiny bill, that it was capable of boring tunnels. into tolerably hard sandstone. Such, however, is the case, for the sand-martin is familiarly known to drive its tunnels into sandstone that is hard enough to destroy all the edge of the knife.' The mode in which this little miner excavates its gallery, at the end of which it places its nest, has been carefully observed and well described by Mr. Rennie, whose name is well known to every naturalist as an admirable observer of the habits of animals.
The bird works with its bill shut. This fact our readers may verify by observing their operations early in the morning, through an opera-glass, when they begin in the spring to form their excavations. In this way we have seen one of these birds cling with its sharp claws to the face of a sandbank, and peg in its bill as a miner would do his pickaxe, till it had loosened a considerable portion of the hard sand, and tumbled it down among the rubbish below. In this preliminary operation it never makes use of its claws for digging: indeed, it is impossible it could, for they are indispensable in maintaining its position, at least when it is beginning its hole. We have further remarked that some of these martin's holes are nearly as circular as if they had been planned out with a pair of compasses, while others are more irregular in form: but this seems to depend more on the sand crumbling away than upon any deficiency in the original workmanship. The bird, in fact, always uses its own body to determine the proportions of the gallery, the part from the thigh to the head forming the radius of the circle. It does not trace this out as we should do by fixing a point for the centre around which to draw the circumference; on the contrary, it perches on the circumference with its claws, and works with its bill from the centre outwards; and hence it is that in the numerous excavations recently commenced, which we have examined, we have uniformly found the termination funnelshaped, the centre being always much more scooped out than the circumference. The bird consequently assumes all positions while at work in the interior, hanging from the roof of the gallery with its
back downwards as often as standing on the floor. We have more than once, indeed, seen a bank martin wheeling slowly round in this manner on the face of a sandbank, when it was just breaking ground to begin its gallery. All the galleries are found to be more or less tortuous to their termination, which is at the depth of from two to three feet, where a bed of loose hay and a few of the smallest breast feathers of geese, ducks, or fowls is spread with little art for the reception of the eggs. It may not be unimportant to remark also that it always scrapes out with its feet the sand detached by the bill; but so carefully is this performed that it never scratches up the unmined sand, or disturbs the plane of the floor, which rather slopes upwards, and of course the lodgment of rain is thereby prevented.'
There has been much difference of opinion with respect to the excavating habits of the common kingfisher-some maintaining that it is a true miner, others, and apparently with more evidence on their side, asserting that it merely makes use of some readymade hole in the bank. Certainly there is nothing in the structure of this bird to forbid its being able to excavate its own home, its strong conical beak being well adapted to pierce sandstone or earthy banks. The deserted burrows of the water-vole are not unfrequently taken possession of by the kingfisher, which enlarges and adapts them to its own necessities. In all cases the bird takes care to increase the size of the burrow at the spot where the nest is made and to choose a burrow that slopes upwards, so that however high the water may rise, the nest will be perfectly dry.' Those who have examined the nest of the kingfisher have always found in it a large quantity of comminuted fish-bones. It is well known that the kingfishers, like the predacious birds, cast up from their crops the indigestible portion of their food; and in the kingfishers this consists chiefly of the bones of minnows, sticklebacks, young trout, &c. &c. Now it has long been a disputed point amongst naturalists as to whether the bird designedly deposits these castings in the hollow as a stratum on which to lay her eggs. On the negative side is Mr. Rennie, who thus writes in his edition of Montague's Ornithological Dictionary' :
In the bank of a stream at Lee, in Kent, we have been acquainted with one of these nests in the same hole for several successive summers, but so far from the exuviæ of fish bones ejected, as is done by all birds of prey, being dried on purpose to form the nest, they are scattered about the floor of the hole, in all directions from its entrance to its termination, without the least order or working up with the earth, all moist and fetid. That the eggs may by accident bo laid upon portions of these fish-bones is highly probable, as the floor is so thickly strewed with them that no vacant spot might be found, but they assuredly are not by design built up into a nest. . . . It frequents
the same hole for a series of years, and will not abandon it though the nest be repeatedly plundered of the eggs or young. The accumulation of cast bones in one of these holes has perhaps given origin to the notion of the nest being formed of them.'
But in favour of the other view there is a very high authority, namely, Mr. Gould, who succeeded in removing the kingfisher's nest entire and placing it in the room of the British Museum devoted to such objects. This example represents a flat-surface of aggregated fish-bones of about half an inch in thickness, with a very shallow depression in the centre; there is no admixture of sand or soil, the nest consists entirely of fish-bones. This case has been generally, we believe, considered sufficient to establish the fact that the kingfisher always forms these bones into a nest, and does not merely lay her eggs at random upon the ejectment. We confess we do not see that the question at issue is so settled as to negative the other assertion, though it is sufficient, perhaps, to modify it. Our own experience of kingfishers' nests is in favour of Mr. Rennie's opinion. We have examined a nest after the bird had laid two or three eggs, and found the fish-bones scattered about and mixed promiscuously with the sand on the floor of the hole.
The curious puffin or sea-parrot often digs its own burrow, but also not unfrequently disputes the possession of a ready-made rabbit-hole with that animal. The males principally engage in the work of excavation; the holes extend to the depth of three feet, and have occasionally two entrances. The single egg which sea-birds usually lay is deposited at the end of the tunnel on the bare ground without any materials to form a nest. Mr. Seely tells us that the puffins are so intent upon their work of excavation that they may often be taken by the hand at that time. stormy-petrel, so dreaded by superstitious sailors, and the smallest web-footed bird known, is, we are told, an accomplished miner in such localities where no ready-made holes exist. Off Cape Sable, in Nova Scotia, there are many low-lying islands, the upper parts of which are of a sandy nature and the lower composed chiefly of mud. Not a hope is there in such localities of already existing cavities, and yet to those islands the petrels resort by thousands for the purpose of breeding. The birds set resolutely to work and delve little burrows into the sandy soil, seldom digging deeper than a foot, and, in fact, only making the cavity sufficiently large to conceal themselves and their treasure.' The sailors imagine that the stormy-petrel never goes ashore nor rests, that it does not lay its egg on the ground, but holds it under one wing and hatches it while flying!
The woodpeckers, of which there are at least three undoubted species
species belonging to our own country, but which are gradually becoming more and more scarce, will furnish us with interesting instances of wood-tunnelling birds. It would not be easy to mention any other created thing which by its structure evinces more perfect adaptation of means to an end than these beautiful birds. Possessed of a strong-pointed beak wherewith to pierce a hole-with feet and tail admirably suited to retain the bird firmly fixed to the tree on which it is at work-with a remarkably shallow keel of the breast-bone, so as to allow it to place its body close to the wood and to diminish the labour of ascending-the woodpecker is eminently fitted for its peculiar mode of life. The woodpeckers of this country, however, are not able to make holes in sound wood, and always choose such timber as is either already dead or has begun to decay. Sometimes the bird selects a spot where a branch has been blown down, leaving a hollow in which the rain has lodged and eaten its way deeply into the stem. In such places the wood is so soft that it can be broken away with the fingers or scraped out with a stick; and in many a noble tree which seems to the eye to be perfectly sound, the very heart wood is being slowly dissolved by the action of water which has gained access through some unsuspected hole. Oftentimes a large fungus will start from a tree, and in some mysterious manner will sap the life-power of the spot on which it grows. When the fungus falls in the autumn it leaves scarcely a trace of its presence, the tree being apparently as healthy as before the advent of the parasite; but the whole character of the wood has been changed by the strange power of the fungus, being soft and cork-like to the touch. Although the eye of man cannot readily perceive the injury, the instinct of the woodpecker soon leads the bird to the spot, and it is in this dead, soft, and spongy wood that the burrow is made.' Our own celebrated naturalist, Waterton, was, Mr. Wood believes, the first to point out this fact, and showed him many examples of the fungus and its ravages among the trees, several fine ashes and sycamores having been reduced to mere stumps by the silent operation of the vegetable parasite.
The North-American woodpeckers, however, are furnished with more powerful boring-instruments, and are able to hollow out for themselves dwellings in the sound wood, though they generally select that which has already begun to decay. Preeminent amongst these birds is the great ivory-billed woodpecker (Picus principalis) of Brazil, Mexico, and other Southern States. So incessantly does this bird work with his hard pickaxe-shaped bill, that in an hour or two, according to Catesby, he will form a bushel of chips, on which account the Spaniards call these birds 'carpinteros.' The same writer tells us that the Canadian Indians