THE BIRDS OF MONGOLIA ETC. 49 



the 10th of March in small numbers, whilst the principal migration takes 

 place in the end of this month ; at this time the birds keep together in flocks, 

 sometimes in company with Herodias alba, Grus leucogeranus, or Ibises. 



They are extremely cautious, and choose for their nesting-places the small, 

 thick, reedy islands of the river Lefa, which runs into Lake Hanka. Here 

 the nests are very numerous, close to each other, all being built of the same 

 shape and very carelessly. Some twigs, without any lining, form the whole 

 structure, which is of a flat shape and not elevated beyond two or three feet 

 above the water-mark. It is difficult to understand how the eggs do not get 

 injured in these nests during a strong wind. 



I visited the above-described locality in the middle of June, when the 

 young had partly left their nests, whilst the others were just at the point of 

 doing so. 



During the autumnal migration (i. e. in September and beginning of 

 October) I met with many flocks of these birds on the coast of the Japanese 

 Sea. 



224. Herodias alba, L. Zaplia helaya. 



We observed this bird in S.E. Mongolia only on one occasion, on the 

 marshes of the Hoang-ho valley, in large numbers ; it apparently breeds 

 there. 



The first migrants appeared in Tsaidam on the 18th of February, 

 notwithstanding the heavy snowfalls and frost of 1 2° C. 



At Koko-nor we observed these birds only about the end of March, 

 singly or in pairs. 



At Lake Hanka they are as common as the preceding species, and arrive 

 usually at the same time with it, about the middle of March. 



H. alba does not form large flocks, but, as a rule, lives singly, in pairs, 

 or in small flocks. In the middle of April, those which stop here disperse 



VOL. III. H 



