J. E. LITTLEBOY — THE MIGRAIIOX OF BIRDS. 37 



those of stronger organisation, so that these would for the most 

 part hcoonie the progenitors of a keen-sighted and observant race." 

 The immense lieight at whicli migration is generally accomplished 

 renders the discernment of distant objects a comparatively easy 

 task ; the rocky island and the far-off coast, lie, like an extended 

 map, within the ken of the little migrant, and it shapes its course 

 accordingly. Important information respecting this phase of the 

 subject has been obtained by telescopic observation. I quote a few 

 lines from a letter by J. Tennant, E..E., which appeared some years 

 ago in 'Nature':* — "Looking at the sun this morning, I saw 

 birds very frequently pass the disc. Some were in focus with the 

 sun itself, the wings being quite sharp against the disc, and must 

 have been several miles liigh, but some were much nearer, and I 

 estimate their distance from me at about two miles." " The theory 

 that migration ordinarily takes place at high elevations," and that 

 it is guided by sight, is said to be " supported by the fact that it is 

 only in dark and cloudy weather that migration on a large scale 

 is observed." On such occasions the power of sight is useless ; all 

 landmarks are obscured by clouds, and birds are compelled to 

 descend in order to find their way. It is a remarkable fact that 

 *' in dark nights the stream of migration stops suddenly when the 

 moon rises." 



The great rush of autumnal migration takes place, almost always, 

 in the month of October. A few " avant-courriers,1[ supposed to 

 consist of barren birds or birds that have been unable to find mates, 

 appear at uncertain intervals for weeks before the regular period of 

 migration is due." Strange to tell, it is young birds which have 

 never before attempted to migrate that are the first to start. It 

 would seem that a restless hereditary impulse impels them to 

 migrate, and the result is very frequently fatal. It is believed that 

 myriads of young birds perish ; some are taken out to sea, while 

 others, and "their name is legion," lose their way and wander far 

 away, in directions where bird-life is impossible during the winter 

 months. Stray birds are almost invariably young birds ; a rare 

 migrant, whether in England or elsewhere, is nearly certain to be 

 a bird of the year. Certain it is, that the number of birds which 

 return northward in the spring is infinitely smaller than the autumn 

 flight. The autumnal migration of a particular species continues 

 day by day or week by week, till it attains its maximum in a " great 

 rush." Old birds, which know the way, are fond of loitering 

 about wherever an inviting resting-place is found ; by-and-bye frost 

 or a severe storm renders flight a necessity, and hence the final 

 rush. 



The direction of the wind is found to exercise considerable 

 influence on migration. I quote a few lines from a paper by Mr. 

 J. A. Harvie-Brown and Mr. John Cordeaux in the ' Zoologist.' I 

 "In the great majority of cases birds migrate flying within two 



• Vol. xiii, p. 447— April, 1876. • 



t ' Siberia,' p. 255. 



X Third series, vol. iv, p. 187. 



