36 J. E. LITTLEBOY THE MIGEATION OF BIEDS. 



fieldfare, and redwing ; and then sparrows, linnets, and chaffinches 

 compose the bulk of the immigrants. Others, as the redstart, 

 wheatear, whin chat, stonechat, and other soft-billed insect-eatei's, 

 although coming from the eastward, after striking the coast, per- 

 sistently follow the shore-line to the south." 



There are other lines of migration to which I must allude, 

 nights of migrants come to us from the north-east. These follow 

 the coast-line of JS^orway, southward, until they reach its most 

 westerly point, and thence cross the sea, first to the Shetland Islands, 

 and then to the mainland of Scotland. Others reach our shores 

 from the north. It is believed that they pass the summer months 

 in Iceland and Greenland, and that, leaving Iceland in the autumn, 

 they wing their way southward, via the Faroe Islands, to the north 

 of Scotland and north-east of Ireland. These are principally 

 composed of swans, geese, ducks, and waders, but the white wagtail, 

 redwings, blackbirds, redbreasts, meadow-pipits, snow-buntings, 

 and other species are to be found among them. 



It is difficult to account for the vast extent of ocean that is 

 covered by the migration last mentioned. The explanation both 

 of it and of the east to west flight said to be adopted by the stone - 

 chat, points, in all probability, to a period when, according to 

 Professor Edward Forbes, Iceland was linked to Great Britain, and 

 Great Britain to Germany, by extensive plains of dry land.* If 

 this theory should be fully confirmed, it will follow that the 

 habit of migration, once formed, must have been handed down 

 through countless generations, and that the course pursued by 

 migrants, under geological conditions very different from those 

 which now exist, is continued to the present day. 



Birds are provided with certain peculiar faculties which render 

 such flights practicable. That their organ of locality is developed 

 to an unusual extent, is shown by the extreme ease with which 

 they thread the intricacies of the densest forests, and return with 

 certainty to the sechided nook selected as their home. That their 

 power of vision is something altogether extraordinary, there is also 

 abundant evidence to prove. The hawk, as it hovers far aloft, 

 distinguishes the little mouse which creeps along the hedge-side 

 below, and darts upon its tiny prey with an unerring aim. The 

 carrier pigeon, when released from confinement, rises at once high 

 in air, takes the bearings of its position, and guided, as is generally 

 believed, by sight alone, darts oft' with absolute certainty to its 

 far-distant home. 



The very existence of migratoiy birds must constantly depend 

 on the possession of these powers, and it is highly probable that 

 the influence of natural selection has played an important part in 

 their attainment. The case is well put by Dr. Weissmann : f — 

 " Individual birds of imperfect sight are more likely to lose their 

 way and to fall victims to some of the dangers of the journey, than 



* 'Memoirs of the Geological Survey of Great Britain,' vol. i, pp. 397-8. 

 t 'Contemporary Review,' vol. xxxiv, p. 550. 



