THE BIRDS OF MONGOLIA ETC. 163 



The first migrants arrived at Muni-ul on the 9th of April, and in Kan-su on 

 the 26th of the same month. 



Extremely interesting is Pere David's observation (mentioned by 

 Swinhoe*) that in the mountains about Pekin these Swallows sleep during 

 the winter in caverns, which they only leave on fine days in winter for a few 

 hours. 



Measurements: — 





Length. 



Widtli. 



Wing. 



Tail. 



Tarsui 





in. 



in. 



in. 



in. 



in. 



c? . 



4-8 



11 



5-45 



244 



0-4 



2 . 



? 



? 



5-24 



2-35 



0-4 



34. Chelidon cashmerensis, Gould. 



Was found by us in great numbers in the Ala-shan mountains and in 

 Kan-su. In S.E. Mongolia they are rather scarce ; they might possibly 

 breed in Hara-narin-ul, but certainly do not occur in Muni-ul at any other 

 time than during migration. It avoids the habitations of man, and keeps to 

 the wild rocks of lofty mountains. In Kan-su, for instance, it breeds mostly 

 in the alpine region, at heights of from 10,000 to 12,000 feet above the sea ; 

 it is very rare in the median zone, and descends to the low parts when in 

 search of food. 



The nests, several in a row, are stuck to overhanging rocks, and by their 

 shape resemble those oi Hir undo guttur alls. On the 25th of June I climbed 

 up two, and found in one of them two and in the other four young, almost 

 fledged. 



In Kan-su the first birds arrived on the 20th of April, and left about the 

 middle of August. We at this time observed tolerably large flocks flying 

 southwards. 



Our specimens from Kan-su differ from Gould's description by being 



^ Proc. Zool. Soc. 1871, p. 347. 



z 2 



