162 THE BIRDS OF MONGOLIA ETC. 



Din-juan-in, close to the Ala-shan mountains, a nest with some unfledged 

 young in it. 



It arrives in S.E. MongoKa much later than Hirundo gutturalis (i, e. about 

 the 10th of May), although in the mountains of Kalgan we once observed it on 

 the 23rd of April. The first birds in Kan-su were seen on the 14th of May. 

 The autumnal migration takes place in the early part of September ; and on 

 the 12th of this month we saw a large flock about the river Tetunga, which 

 occupied about two hours in passing us. In Ussuri country we only once 

 observed it. 



32. CoTYLE RiPARiA, L. Lastochka semliannaya. 



Is tolerably common in S.E. Mongolia, but is rather scarce about Ordos 

 and Ala-shan, and does not occur at all in Kan-su. It breeds in the former 

 localities in small companies of from three to five pairs, on the sides of rivulets, 

 and sometimes in the hills of the steppe at great distances from the water. 

 On the 6th of June I took a nest with six perfectly fresh eggs ; and on the 

 18th of the same month we found some young birds. 



They arrive in spring in S.E. Mongolia at the end of April, and leave at 

 the end of August ; on the 20th of this month we observed, in the Hoang-ho 

 valley, an enormous flock migrating south. 



In Ussuri country and the basin of the Hanka we never met with Cotyle 

 riparia ; nevertheless it breeds in the Amur district. 



33. Cotyle RUPESTRis, Scop. Lastochka gornaya. 



Is common in the mountains of S.E. Mongolia and Kan-su. In the 

 latter place they do not ascend as high as the alpine region. They spend 

 whole days in flying about the rocks where they breed. Their nests are 

 usually stuck to protruding stones, or roofs of small caverns in the rocks. 



