THE AUTUMN MIGRATION OF BIRDS. 227 



volume month by month, until it is in the full 

 tide of its movement, and the temperate zones of 

 the Northern Hemisphere are once more teeming 

 with pilgrim birds. Now the general direction is 

 from north to south, but many pass from north- 

 east to south-west, and from north-west to south- 

 east, the fly-lines crossing each other just as intri- 

 cately as in spring. In the Palacarctic region we 

 have also a very important stream of Migration 

 flowing nearly due West from the East ; another and 

 a smaller stream setting in due East from the West. 

 We shall have occasion again to allude to these 

 various streams of migrants later on. The great 

 intensity of Migration Flight is much more sudden 

 in autumn than in spring, often great numbers of 

 birds appearing at once, not gradually becoming 

 more and more numerous ; the ebb is about the 

 same. Another very remarkable fact connected 

 with Autumn Migration is, that the birds observed 

 on passage are much more abundant than in spring, 

 and that the tendency to fraternize among in- 

 dividuals, as well as among species, is greater. 

 Young birds especially are prone to this gregarious 

 habit, and of course it is of these young birds that 

 the great majority of autumn migrants consists. 

 As soon as ever the broods are sufficiently matured 

 to be independent of parental care, a gregarious 

 instinct becomes predominant, especially among 

 Waders, and flocks are soon formed at the common 

 feeding-ground which eventually start ofFon migration 

 in company. The old birds are delayed somewhat. 



