22 STUDIES IN BIRD-MIGRATION 



plished via Norfolk and Lord Howe's Islands by three 

 flights, two of 550 miles and one of 600 miles. Another 

 remarkable feat is that performed by Warblers, Pipits, 

 Shrikes, and Sandpipers, across the Himalayas, when 

 travelling to and from Siberian and Central Asiatic 

 summer quarters to In.dian winter retreats. These 

 birds traverse a belt of absolute desert of more than one 

 hundred miles in width, having an elevation of over 

 15,000 feet, and intersected by numerous snow-capped 

 ridges, the lowest passes of which are 18,000 feet 

 above sea-level. These, Hume tells us,^ present no 

 invincible obstacles to even the tiniest and most 

 feeble-winged migrants, such as the Warblers of the 

 genus Phylloscopus. 



Migration by Night. — These journeys are wonderful 

 in many ways, but how very much more wonderful do 

 they become, when it is remembered that they are chiefly 

 performed during the hours of darknesS' — indeed, almost 

 invariably so, when a considerable expanse of sea has to 

 be traversed ! Why night travelling should be resorted 

 to is one of the most puzzling of the many problems that 

 are associated with the phenomena of bird-migration ; 

 yet I think it admits of reasonable explanation. Here 

 again, food seems to me probably to play an important 

 part. It is well known that most of the daytime has to 

 be devoted by birds to the search for food. Let us 

 suppose that the traveller sets out to cross the North Sea 

 in the daytime. What would this imply ? It would mean : 

 (i) that the voyager must undergo a fast of many hours 

 during its passage across the sea ; (2) it would reach 

 our shores at night or during the early hours of the 

 morning, and many hours must again elapse ere food 



' Henderson and Hume, Lahore to Yarkand, pp. 160-1. 



