770 BIRDS [SONG. they shift from place to place in its quest, arid may thus find an easy way of accounting for their uncertain appear- . ance. The great band of Nutcrackers (NwAfraga caryo- catactes) which iii the autumn of 1844 pervaded Western and Central Europe 1 may also have been actuated by the same motive, but we can hardly explain the roaming of all other Birds so plausibly. The inroads of the Waxwing (Ampelis garrulus) have been the subject of interest for more than 300 years, and by persons prone to superstitious auguries were regarded as the forerunners of dire calamity. Sometimes years have passed without its being seen at all in Central, Western, or Southern Europe, and then perhaps for two or three seasons in succession vast flocks have sud denly appeared. Later observation has shown that this species is as inconstant in the choice of its summer- as of its winter-quarters, and though the cause of the irregularity may possibly be of much the same kind as that just sug gested in the case of the Crossbill, the truth awaits further investigation. 2 One of the most extraordinary events known to ornithologists is the irruption into Europe in 18G3 of Pallas s Sand-Grouse (Syrrhaptes paradoxes). Of this Bird, hitherto known only as an inhabitant of the Tartar steppes, a single specimen was obtained at Sarepta on the Volga in the winter of 1848. In May 1859 a pair is said to have been killed in the Government of Vilna on the western borders of the Russian Empire, and a few weeks later five examples were procured, and a few others seen, in Western Europe one in Jutland, one in Holland, two in England, and one in Wales. In 1860 another was obtained at Sarepta; but in May and June 18G3 a horde computed to consist of at least 700 individuals overran Europe reaching Sweden,Norway,the Faeroes, and Ireland in the north-west, and in the south extending to Sicily and almost to the frontiers of Spain. On the sandhills of Jutland and Holland some of these birds bred, but war was too successfully waged against the nomades to allow of their establishing themselves, and a few survivors only were left to fall to the gun in the course of the following winter and spring. 3 In the summer of 1872, another visitation to Great Britain was reported, but if it really took place it must have been that of a very small number of birds, and it was not observed on the Continent. Speculation has amused itself by assigning causes to these movements but the real reason remains in doubt. We cannot quit the subject of Migration, however, with out referring to the wonderful assemblages of Birds which have in various places been time and again noticed by night. Towards the close of summer, in dark, cloudy, and still weather, it not unfrequently happens that a vast and, to judge from their cries, heterogeneous concourse of Birds may be heard hovering over our large towns. The practical ornithologist will recognize the notes of Plover, Sandpiper, Tern, and Gull, now faint with distance and then apparently close overhead, while occasionally the stroke of a wing may catch his ear, but nothing is visible in the surrounding gloom. Sometimes but a few fitful wails are heard, of which only an expert listener will know the meaning. At others the continuous Babel of sounds will ensure the attention of the most incurious. It is supposed that these noises proceed from migrating birds, which, having lost their way, are attracted by the glare of the street-lamps, but far too little has been observed to remove the obscurity that in a double sense surrounds them and to enable us to come to any definite conclusion. It must be added also that such a concourse has been noticed where the fascina- 1 Bull, de 1 Acad. de Bruxelles, xi. p. 298. 2 Cf. Yarrell, Brit. Birds, cd. 4, i. pp. 524-532. 3 Ibis, 1864, pp. 185-222. A few additional particulars which have since become known to the writer are inserted above. tion of light did not exist, for Lord Lilford has recorded 4 how that once at Corfu he was startled by an uproar as if all the feathered inhabitants of the great Acherusiau Marsh had met in conflict overhead, but he could form no concep tion of what birds produced the greater part of it. SONG. Leaving then the subject of Migration, the next impor tant part of the economy of Birds to be considered is perhaps their Song a word, however, in a treatise of this kind to be used in a general sense, and not limited to the vocal sounds uttered by not more than a moiety of the feathered races which charm us by the strains they p-our from their vibrating throat, strains indeed denied by the scientific musician to come under cognizance as appertain ing to his art, but strains which in all countries and in all ages have conveyed a feeling of true pleasure to the human hearer, and strains of which by common consent the Night ingale is the consummate master. It is necessary in a philosophical spirit to regard every sound made by a Bird under the all-powerful influence of love or lust as a Song." It seems impossible to draw any but an arbitrary line Vari between the deep booming of the Emeu, the harsh cry of Song the Guillemot (which, when proceeding from a hundred or a thousand throats, strikes the distant ear in a confused murmur like the roar of a tumultuous crowd), the plain tive wail of the Plover, the melodious whistle of the Widgeon, " the Cock s shrill clarion," the scream of tho Eagle, the hoot of the Owl, the solemn chime of the Bell- bird, the whip-cracking of the Manakin, the Chaffinch s joyous burst, or the hoarse croak of the Raven, on the one hand, and the bleating of the Snipe 5 or the drumming of the Ruffed Grouse, on the other, Innumerable are the forms which such utterances take. In many birds the sounds are due to a combination of vocal and instrumental powers, or, as in the cases last mentioned, to the latter oily. But, however produced and of the machinery whereby they are accomplished there is not room here to speak all have the same cause and the same effect. The former has been already indicated, and the latter is its consum mation. Almost coinstantaneously with the hatching of the Nightingale s brood, the song of the sire is hushed, and the notes to which we have for weeks hearkened with rapt admiration are changed to a guttural croak, expressive of alarm and anxiety, inspiring a sentiment of the most opposite character. No greater contrast can be imagined, and no instance can be cited which more completely points out the purpose which " Song" fulfils in the economy of Farp the bird, for if the Nightingale s nest at this early time destroyed or its contents removed, the cock speedily re covers his voice, and his favourite haunts again resound to his bewitching strains. For them his mate is content again to undergo the wearisome round of nest-building and incubation. But should some days elapse before disaster befalls their callow care, his constitution undergoes a change and no second attempt to rear a family is made. It would seem as though a mild temperature, and tile abundance of food by which it is generally accompanied, prompt the physiological alteration which inspires the males of most birds to indulge in the "Song" peculiar to them. Thus after the annual moult is accomplished, and this is believed to be the most critical epoch in the life of any bird, cock Thrushes, Skylarks, and others begin to sing, not indeed with the jubilant voice of spring but in an 4 Ibis, 1865, p. 176. 6 The true cause of this sound has been much discussed, but Herr Meves s explanation (Proc. Zool. Soc. 1858, p. 302), based on experi ment, seems to be correct, though it is far from being generally
accepted.