MIGRATION 571 



manner, though they are not entirely the sport of circumstances. 

 The erratic movements of the various species of Crossbill {Loxia) 

 and some allied forms afford perhaps the best-known examples. 

 In England no one can say in what part of the country or at what 

 season of the year he may not fall in with a company of the com- 

 mon Crossbill {L. curvirostra), and the like may be said of many 

 other lands. The food of these Birds consists mainly of the seeds 

 of conifers, and as its supply in any one locality is intermittent or 

 precarious, we may not unreasonably guess that they shift from 

 place to place in its quest, and may thus find an easy way of 

 accounting for their uncertain appearance. The great band of 

 Nutcrackers (Nudfraga caryocoiades) which in the autumn of 1844 

 pervaded Western and Central Europe ^ 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 Wax- 

 wing {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 suddenly appeared. Later observation 

 has shewn 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 

 suggested in the case of the Crossbill, the truth awaits further 

 investigation. 2 One of the most extraordinary events known to 

 ornithologists was the irruption into Europe in 1863 of Pallas's 

 Sand-Grouse, Syrrhaptes paradoxus. Yet this was thrown into 

 insignificance by the appearance in 1888 of a still vaster horde 

 which followed on the whole the lines of its predecessor. Specu- 

 lation has amused itself by assigning causes to these movements, 

 but the real reason remains in doubt. 



We cannot quit the subject of Migration, however, without 

 remarking that the " rushes " to light-houses and light-ships already 

 mentioned are not confined to marine stations or to places possess- 

 ing the fascination of a Pharos. Toward the close of summer, 

 and well on into autumn, 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 inland 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 surround- 

 ing gloom. Sometimes but a few fitful wails are heard, of which 



^ Bull, de I' Acad, de Bruxelles, xi. p. 298. 



2 Of. Yarrell, Brit. Birds, ed. 4, i. pp. 524-532. 



