A survey must now be made of some of the more remarkable cases whereby more or less musical, or rhythmical, sounds are made by instruments of percussion; or by rapid vibrations. These are in almost every instance formed by varying grades of modification in the feathers of the wings or tail. Their presence, and their use, seem natural enough until we recall the fact that many other birds without any apparatus whatever, make sounds in no way less remarkable or less penetrating. Pigeons, Nightjars and Owls, for example, can produce at will curious snapping sounds by bringing the wings smartly together over the back. The White, and Shoebilled Storks make castanets of the beak, throwing the head backwards till the point of the beak touches the back, when the jaws are set rapidly clashing one against another, producing a sound comparable to the “bones” of negro minstrels, but without the varying rhythm. As this performance is proceeding, the head and neck are slowly moved through half a circle, till the tip of the beak touches the ground, when the music ceases. As with the wing-snapping just referred to, both sexes are equally skilful performers; but while they seem to indulge in such exercises much more frequently, and with more vim during the breeding season, they will break out after this demonstrative fashion at all times of the year. But why, then, the need for the yet more elaborate contrivances which are to be met with among the Snipe, the Game-birds, and certain of the Passeres? However, be this as it may, in a large number of species a special mechanism has been evolved to produce sounds which, as has been remarked, in other species are no less effectually made without that mechanism. One of the simplest of the cases is that furnished by the remarkable “bleating” or “drumming” performances of many species of Snipe, generally, if not only, when sexually excited, and especially of the Common Snipe (_Gallinago cœlestis_) during its love-flights. Mounting to a great height, this bird, at such times, suddenly turns, and descends with prodigious speed, meanwhile holding the tail fully expanded. The outermost pair of feathers are, however, specially modified so that, in the first place, during this descent they stand at right angles to the long axis of the body and well apart from the rest of the tail-feathers. This alone, however, would not produce these weird sounds, which owe their origin to the fact that these particular feathers have their shafts conspicuously thickened and peculiarly curved, while the vane or web of the inner side of the feather is of great width and structurally differs from the vanes of the other feathers, whereby the vane becomes more resistant to the rush of air caused by the wings during the descent.