THE BIEDS OP MONGOLIA ETC. 143 



steppes of Zachar, where L. agotom is extremely abundant, Archibuteo hemi- 

 lasius is found very commonly in the winter, and remains even for the summer 

 in great numbers, building their nests on crookedly grown trees, which are 

 now and then to be found on the plains and on the mountains. West of the 

 Zachar country, where the ground changes, they diminish in number ; and 

 about Ordos and Ala-shan they are very rarely to be met with. 



We only once observed the species in Kan-su, which in great numbers 

 winters in the steppes of Koko-nor, where another kind of Lagomys is very 

 abundant. They seize their prey by dashing downwards or watching it at 

 the hole on the ground. These birds, when occupied with their food, as also 

 at other times, are very tame on the approach of man. They are rare in 

 Tsaidam, and have not been found by us at all in Northern Tibet. 



Besides A, hemilasius, we observed in Mongolia, about Koko-nor, another 

 species of this genus, which was much larger than the present and of a uniform 

 dark brown colour ; but I am sorry to say we could not succeed in obtaining 

 a specimen. 



5. Aquila chrysaetos, L. Orel Holsan. 



One specimen, a middle-aged male, was obtained in autumn at Ala-shan. 

 In S.E. Mongolia we several times observed adult Eagles (with white 

 shoulders) belonging to the present or perhaps to the following species, but 

 did not succeed in killing any. In Kan-su and Koko-nor this bird is scarce, 

 and old birds were not observed there by us at all ; but young of the present 

 and the two succeeding species are very difficult or, rather, impossible to 

 distinguish at a distance. 



Our Ala-shan specimen does not differ at all from European birds of the 

 same age. This has also been noticed by Dybowsky with regard to the 

 Daurian and Lake-Baikal specimens. 



Pere David says that he has seen a different Eagle in Mongolia — i. e. of 

 a larger size, with a longer culmen and a white tarsus. 



