IN the study of the nests and nesting habits of birds, we find that they divide themselves naturally into certain categories as resulting from the different sites they choose for their nests. A large number, as we know, build in trees, high or low, or in bushes, others on the ground, or very near it; some few seek the habitations of man. Another large class build in holes in trees, natural or excavated by themselves, on crags and rocks, in crevices of any kind. Others, again, build on or near water; some utilise the old nests abandoned by previous owners, many make no real nest at all. One species, fortunately unique, not only takes felonious possession of the nests of others, but adds insult to injury by handing on to them as well the weighty burden of the brooding and upbringing of the usurper’s progeny, and this, too, at the expense of their own innocent families.

Probably the most familiar instance of birds nesting in high trees is that of the rooks, a gregarious race, living in large colonies, and preferably near human habitations. Their nest is a crude structure of sticks and twigs, which they bite off with their powerful beaks, with some coarse lining of grass or the like. Their congeners, the carrion crow and hooded crow, on the contrary, nest in single pairs in trees or on cliffs and crags, and generally use some wool in the lining. The magpie, which also prefers solitude, strikes out a line for itself, building a large structure strongly domed and covered with thorns, generally at a considerable height ; possibly a guilty conscience causes it to fear reprisals. The jackdaw is to be found in larger or smaller colonies, nesting in hollow trees, or in holes and crevices in cliffs, or in ruins, or in church steeples ; often, too, as many of us have experienced, in house chimneys.

A distinct type of nest is that of the wood pigeon, a mere platform of sticks and twigs, so sparse that often the eggs may be seen through the bottom ; and yet, although so fragile in appearance, it seems to resist successfully the wildest storms.

Would that we might still number that noble bird, the osprey, among our native tree-building birds. A generation ago its nest might still have been found on some tall pine overlooking the waters of a Highland loch; but the greed of the egg-collector has robbed these scenes of one of their greatest charms. About the most unlikely bird, one would have thought, to choose high trees for its breeding-site, is the heron, and certainly they look somewhat quaint and out-of-place, with their long bare legs, perched on some lofty tree ; yet such is the usual situation for their colonies, although, when suitable trees are wanting, as in our more northern districts, they are to be found building in stunted birches or hollies, on ivy-clad rocks, or even on the heather-clad cliffs. Occasionally, too, although usually gregarious, a single nest is to be found. I well remember such a solitary example on a single tree growing by the side of one of our western salt-water lochs.

Another fine bird that, like the osprey, was not so long ago common throughout Scotland, is now no longer to be found on our side of the border. The kite or 'Bled' builds its large and conspicuous nest usually on a tall and inaccessible tree, and is remarkable for a very singular and unaccountable habit ; for invariably in the lining of the nest will be found rags and tatters of human clothing, paper and the like, acquired no doubt from the nearest farmyard rubbish heap. Robert Gray 1 describes a nest near Loch Lomond, some fifty years ago, as suggesting that 'the bird had robbed some gaberlunzie of his wardrobe, - a pair of ragged trousers, worn stockings, and part of an old shirt, being among the articles.

The kite has little fear of man, and his constant raids on the poultry yards doubtless brought about his destruction. To-day a small remnant still exists, carefully preserved and cherished, in a certain district of Wales.

Of all our British birds the chaffinch is preeminent as the architect of the most beautiful and artistic of nests. Placed, as a rule, at a height intermediate between the higher and the lower building species, the nest is usually so alike to its immediate surroundings as to be easily overlooked. The moss, grass stems and rootlets are deftly interwoven, felted together with spiders' webs, and delicately lined with wool feathers, hair and such like soft materials ; the outer walls spangled with lichens and mosses, the whole so beautifully rounded as to suggest the turning-lathe or potter's wheel rather than the unaided efforts of the tiny builder. Sometimes one finds exceptions to the general rule, as in an example where the whole outer nest was studded closely over with small pieces of white paper, making it a somewhat conspicuous object.

Another nest, hardly less beautiful, is that of the goldfinch, now unfortunately a rare bird with us. This is usually placed much higher than that of the chaffinch and so is difficult to find, is lined with wool and hair, but seldom or never with feathers.

Of a totally different nature are the dome=shaped nests, of which that of the water ouzel may be taken as an example. One of our earliest nesting species, the site is preferably in a rocky hollow or crevice, often so close to some little cascade as to be ever damp from the spray. A large structure for the size of the bird, the chief material used by it is moss, with grass stems, roots, and, in many instances at least, withered, hard wood leaves. Unless the nest is sufficiently covered by the nature of the cavity, the whole is domed and roofed over. Sometimes the site is such that the bird has to pass and repass through spray and falling water to reach the nest. The piers and arches of bridges are also in some cases utilised. Another curious instance is recorded by the late E. R. Alston, as quoted in Dresser's Birds of Europe: 'Sometimes the dipper shows unwonted boldness in its choice of an abode. I have known a pair to build in a hole in a wall to which they could only gain access by darting between the revolving spokes of a mill wheel.

The wren is another well-known dome-building bird, choosing often the overhanging brows of burns or banks or quarries, crevices in rocks, ivy-clad walls and such-like well-protected places. They use a great variety of material, restricting themselves, however, mainly to one substance in each case; one nest, for instance, will be chiefly composed of oak leaves, another of moss, and so on. Many are lined with feathers, others are unlined; it has therefore been sometimes held that the latter were merely sleeping places, or winter houses; but Gray says that of six examples examined by him, and all without feathers, each contained eggs. It is nevertheless evident, from the number of nests found in a restricted area, that some are built and used for residential purposes only.

The most artistic and beautiful of the dome nests is doubtless that of the long-tailed tit. Firmly fixed to the branch of a tree, or in the middle of some thick bush, it is closely woven or felted together, the moss and other material made dense and secure with wool and spiders webs only a small hole left on one side of the oval-shaped nest for ingress; the whole studded with lichens and bark scales so as to match the immediate surroundings. It is somewhat unaccountable why this lovely little creature should, alone of all its congeners, build a nest that to us seems singularly inconvenient in view of its long tail, but so it is. The nest is loosely and warmly lined with a great amount of feathers.

Of birds that build in holes in trees, the wood-peckers select one with some portion sufficiently decayed, and excavate their own retreat with their powerful beaks, the chips below often betraying the locality. One species of this interesting family has of late years begun to return to its old haunts north of the Tweed, and it is earnestly to be hoped that those who are fortunate enough to find them nesting will refrain from giving any hint, however vague, as to the locality in the public press ; for such serves merely to bring down on them the egg-collector and his hungry gang.

A natural hollow in a tree serves often for the nest of the tawny owl, although it frequently uses an old nest of rook or crow, as is the constant habit of the long-eared owl. The white or barn owl is more apt to select church steeples, ivy-clad ruins or crags, although occasionally using tree holes also. These latter are not what one would expect to be the natural breeding-place of any pigeon; yet the stock dove builds by preference in hollow trees, although at times making shift with rabbit burrows when nothing more suitable is handy. Still less, however, would one suspect a duck of such a choice; nevertheless the golden eye nests regularly in hollow trees and often at some considerable height. That gaudily-coloured bird, the sheldrake, on the other hand, lays its eggs in rabbit burrows, sometimes even, we are told on the authority of Dresser, in the earths of fox or badger, and that, too, notwithstanding the presence of the original tenant; yet this is stated also by several foreign authorities, who add that no disturbance of peaceful relations appears to follow.

Of the smaller birds that habitually nest in holes, whether of trees, walls or the like, the great tit, coal tit, blue tit and marsh tit are all familiar examples; and like other birds with similar habits, are ready to take up their abode in suitable nesting-boxes when these are provided for them.

As all know, several species of birds find in and about our own houses convenient breeding places. The house sparrow is the most familiar example, together with the house martin and the swallow; the swift is found nesting under our eaves, as also the starling, while the jackdaw too often takes possession of a disused chimney.

Rocks, cliffs and crags claim quite a number of nesting species. The golden eagle will occur to all as a chief instance; the sea eagle or erne, alas, has joined the osprey and is now nought but a memory. The noble peregrine, however, still holds its place, like the harmless, useful buzzard; and of sea fowl of all sorts, cormorants, shags, gannet, guillemots, gulls and others, it were tedious to make an inventory.

Coming now to such as build on the ground itself, it seems strange to find a falcon with such modest habit; yet the merlin, a true little falcon, is content to build its nest among the heather alongside of the grouse, plover and snipe, of whom, one fears, he is hardly a kindly neighbour. Nor does the same moorland heather-bush suggest itself as the most likely nesting-site for any owl; yet it is there that we shall often find the home and nursery of the short-eared owl, not an uncommon breeding species with us north of Tweed.

Our game-birds all nest on the ground, although naturally in different localities and surroundings, from the capercaillie and the woodcock in the woods to the ptarmigan among the grey lichen-covered boulders of the hill-tops. Of lesser birds too, a great host ; man's familiar friend the robin, the tiny willow-warbler, the wheatear, wagtails, pipits, yellow-hammer, to name only a few that first suggest themselves.

As has been said above, some birds are apt to take advantage of the deserted nests of others. Sometimes, indeed, do not await desertion, but take possession vi et armis; as in the common instance of the house sparrow and the martin. The kestrel will at times be found in possession of an old nest, so too the owls, especially the long-eared owl; a squirrel's drey is sometimes selected, or the nest of crow or magpie.

Still to be considered are those that live and nest on or near to water. The ducks furnish their nest with a warm lining of down from their own breasts, with which they cover carefully their eggs when leaving them; a microscopic examination of these various downs tells the secret of the species to the expert, should the parent bird have escaped unseen. The coot makes a great pile of reed-stalks that can rise and fall to some extent with the varying height o{ the water. The water-hen's nest is somewhat similar, but is usually placed among the rank grasses and herbage at the water's edge. The sandpiper's is generally not very far from the water, although in a recent instance one built more than one hundred yards from the loch side, with a high road and a railway intervening.