THE ZOOLOGY OF SIBEEIA. 465 



riau Fauna, the winter Avifauna of this region being purely Euro- 

 pseo- Asiatic. The remaining and larger portions of the Eastern- 

 Siberian species may be divided into two categories — the first (45) 

 consisting of purely Siberian species or such as only occur in Europe 

 as rare stragglers — the second (240) of species common to Europe 

 and Siberia. 



Again, of the 328 Eastern- Siberian species, 50 only can be consi- 

 dered as true permanent residents of this country, and but nine of 

 these remain during the long and severe winter on the high and bare 

 steppes of Northern Mongolia, These are 



1. Aquila chrysaetos, 6. Passer domesticus. 



2. Strix tengmalmi. 7. montanus. 



3. bubo. 8. Corvus corax. 



4. Alauda Mongolica. 9. Perdix cinerea. 



5. alpestris. 



To these, however, may be added the names of about seven 

 winter-visitants of greater or less frequency, so that the whole 

 winter Ornis of the Mongolian high-steppes may embrace some 

 sixteen species. But when we descend from the steppes into the 

 lower wooded region of Eastern Siberia the winter Avifauna is consi- 

 derably augmented, embracing as many as 61 species — the permanent 

 residents being slightly added to by a few immigrants from the north. 



"We have not now space left to enter upon the very full and 

 interesting particulars given by Herr Eadde concerning the arrival 

 and departure of the migratory birds of Siberia, to the observation 

 of which he appears to have devoted almost unparalleled care and 

 attention. It may be sufficient to say that the results arrived at by 

 von Middendorf in his learned memoir " Die Isepiptesen Eusslands,'* 

 are abundantly confirmed by Eadde' s observations. Tlie most im- 

 portant of them are — 



1. The high table-land of Asia and the bordering ranges of the 

 Altai, Sajan, and Dauria, retard the arrival of the migratory birds. 



2. Eastward of the Upper Lena towards the east coast of Siberia 

 a considerable retardation of migrants is again noticeable. 



3. The times of arrival at the northern edge of the Mongolian 

 high-steppes are altogether earlier than those of the same species on 

 the lower Amoor. 



We have thus endeavoured to give a brief account of some of the 

 more remarkable facts relating to the Siberian Avifauna put forw^ard 

 by Herr Eadde in the present volume. Of the value of this, as of 

 the previous works of a similar character published by the Eussian 

 Naturalists; and of their material influence on the progress of science 



