THE BIRDS OF MONGOLIA ETC. 109 



several times also in the Ala-shan plains, whither they probably go in search 

 of lizards, as we often found in their stomachs the remains of these reptiles. 

 We did not find it either in Koko-nor or Halha. 



282. Larus occiDENTALis, Aud. Chaika sapadnaya. 



Extremely common during migration in S.E. Mongolia about the end of 

 March ; and Ave repeatedly met with them about that time at Dalai-nor, 

 where they probably breed. We did not see any on the Hoang-ho valley in 

 summer, but came across a small flock in September about Din-hu. It does 

 not occur in any other locality traversed by us. 



283. Larus ichthyaetus, Pall. Chaika ribolov. 



Obtained only at Koko-nor, where the earliest migrants appeared on the 

 5th of March, and became very abundant about the 15th of the same month. 

 'J'hey very often occupied themselves in large flocks, together with Graculus 

 carlo, in taking fish out ofXake Buhain-gol ; and as soon as a fish was 

 caught a fight was certain to ensue. The voice of these birds is very loud, 

 and highly disagreeable. 



In China proper, as well as on the Amur and all over Eastern Siberia, 

 these Gulls do not occur; and therefore not only the northern, but also 

 the eastern boundary of their distribution is formed by the Koko-nor. 



284. Chroicocephalus brunneicephalus, Jerd. 



Henderson & Hume, Laliore to Yarkand^ pi. xxxii. 



During the spring migration, which commences about the middle of 

 March and continues until the middle of April, we often met with these birds 



