124 BIRD-LIFE OF THE BORDERS 



twice each year, over vast distances (often thousands of 

 miles) of sea and land ? 



I suggest, in the first place, that no one has ever 

 seen the process of migration in actual operation. Migrat- 

 ing birds are, of course, seen at lightships and light- 

 houses, and in many analogous cases. But that is not the 

 process of migration. It is merely its termination, as the 

 birds make good their landfall. 



The extent of the migratory impulse in birds has 

 already been emphasised. That impulse is all but 

 universal. It follows that a very large proportion of its 

 whole bird-population leave this country (and every 

 northern country) every half-year, and return thereto 

 during the other half. Thus the actual numbers of 

 birds on the move are utterly incalculable — a tangle of 

 figures beyond computation. 



Put it this way : That acres and square miles of 

 birds pass and repass twice yearly over, say, half the 

 earth's superficies, land or water. Yet no one sees 

 them. Every September you see the assembling of 

 swallows on dead trees or telegraph-wires— next day 

 they are gone. But none see them go, or see them on 

 transit. Swallows are but one species, and we have in 

 England 200 or 300 species that migrate. Migration, in 

 fact, is effected as far beyond our vision, as its means 

 lie beyond our knowledge. 



There is always abundant evidence of the progress of 

 migration, although the process is invisible. For the 

 observation of migration, not many ornithologists can 

 have enjoyed wider opportunity than the author, during 

 upwards of fifty over-sea voyages, out and home, 

 including the North Sea and Cattegat, Arctic and 

 Atlantic (North and South), Mediterranean, Red Sea, 



