22б FLIGHT OF BIRDS. 



SO materially retarded vegetation that its aspect 

 differed very little at the end of the month from that 

 which it had presented at the beginning. Although 

 by the second week in March thirteen kinds of 

 birds ^ had made their appearance, it was only singly 

 or in small numbers ; and how rapid must their 

 flight have been over the terribly cold deserts of 

 Northern Tibet, where they could have procured 

 neither food nor water ! 



We arrived on the shores of Lake Koko-nor in the 

 middle of March and found the season as backward 

 as it had been in Tsaidam a month earlier. The 

 lake was entirely frozen over, and even the rapid 

 Pouhain-gol was only here and there free from the 

 ice, which in winter attained a thickness of three feet. 

 Here, too, migratory birds were even less numerous 

 than in Tsaidam. The cause of this difference in 

 the climate of two countries lying in such close 

 proximity to one another is, first, the great eleva- 

 tion of the Koko-nor basin, and, secondly, the influ- 

 ence which the great expanse of its waters exercises 

 over the surrounding countr}\ This sufficiently 

 accounts for the contrast in the climates, which is so 

 marked that it is even noticed by the inhabitants. 



We determined to remain by the lake till the end 

 of April to observe the flight of birds ; and with this 

 object in view we stationed ourselves at the mouth 



' They appeared in the following order : Anas riffila, A. boschas, 

 Linota brevirostris, Mergns merganser, Tnrdus rujicollis, Cygniis 

 musicus, Anas crecca, Vanellus cristatus, Ardca alba, Anser cincreus, 

 Anas acuta, Anthus pratensis? (occasionally wintering in Tsaidam), 

 and Cms virgo. 



