2 30 THE MIGRATION OF BIRDS. 



The Autumn Migration of most birds is much 

 more marked than in spring, and the vast flocks 

 of certain species that may be regularly witnessed 

 passing to their winter quarters exceed in numbers 

 anything seen in the Vernal movement, even in the 

 Arctic regions. For instance, the Little Bustard 

 {Otis tetrax) is described as crossing the Caucasian 

 Steppes on autumn migration literally in millions ; 

 the flights of Sky Larks {Alauda arvensis) at that 

 season are almost past belief, crossing certain points 

 for days and nights together in one scarcely broken 

 stream. Prjevalsky observed the Needle-tailed 

 Swift [Chcetura caudacuta) on autumn passage in 

 Mongolia passing overhead for an entire day almost 

 without cessation. The vast hordes of Waders seen 

 on passage are also most characteristic of autumn. 



If the predominant direction of Autumn Migration 

 in the Northern Hemisphere is from North to South, 

 many minor streams take a different course. Un- 

 questionably the most important of these is the one 

 that sets in from the East and follows a course 

 nearly due West, in the Pal^arctic region. This 

 peculiar, yet very marked, stream of Autumn Migra- 

 tion is as yet far from being perfectly understood, 

 although its existence is a demonstrable fact. It 

 is composed of many species of birds, such as 

 Larks, Starlings, Thrushes, Crows, and Finches, 

 that breed more or less abundantly in Eastern 

 Europe and Western Asia, for the most part hardy 

 species, not exactly obliged to winter in India, or 

 evxn in North Africa, but forced to leave their 



