BIRDS AND THEIR VOYAGES 93 



together, for both by light and night they utter, as 

 they move, an almost unceasing call. The fieldfare's 

 coarse " chack " and the small, piercing note of red- 

 wing or thrush in the flock were constantly uttered 

 during the voyage I watched, though it was broad day. 

 These things throw no light on the question, " How 

 do the travellers know their way through the trackless 

 air across land and water?" Indeed, denying that 

 leadership or the experience of individual birds is a 

 factor in migration, only makes the problem seem the 

 deeper. It may be said: "They find their way by 

 some sense call it the sense of direction distinct 

 from and additional to those we are familiar with." 

 But I would rather lean to the view that the secret 

 sign-posts, the guides through space, which direct the 

 birds, are due to the subtilisation of ordinary senses. 

 Physical senses, which in us, through comparative 

 disuse, have stood stock-still for ages, have in wild life 

 been refined till they hardly resemble our crude ones. 

 We cannot forget this in considering the skill and 

 feats of animals. The manner in which wild creatures 

 mates or companions keep in touch with one 

 another, without being at the least pains to do so, is 

 often a little wonder to the watcher. Here is good 

 sign of that subtle refinement and that working 

 together of the ordinary senses which exists in birds, 

 mammals, insects. It is this refining of the senses 

 and this working of them that avail so greatly in the 

 long travels of wild creatures as in the short ones. I 



