MIGRATION 571 
manner, though they are not entirely the sport of circumstances. 
The erratic movements of the various species of CROSSBILL (Lozia) 
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 (LZ. 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 (Nucifraga caryocatactes) 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 
1 Bull. de Acad. de Brusxelles, xi. p. 298. 
2 Of. Yarrell, Brit. Birds, ed. 4, i. pp. 524-532, 
