THE AUTUMN MIGRATION OF BIRDS. 233 



and join the western instead of the south-eastern 

 stream of birds. At each period of migration, 

 therefore, whether in spring or whether in autumn, 

 we have the curious fact presented to us of two 

 very important minor streams of migration con- 

 currently flowing from West to East and from East 

 to West along one common route ! Rose-coloured 

 Pastors, Rose Finches, and Black-headed Buntings, 

 for instance, on their way from Europe to India, 

 actually pass the western stream of migrants from 

 Asia, with odd White-winged Larks and Richards' 

 Pipits intermingled on their way to Europe ! These 

 bye or minor streams of autumn migrants are for 

 the most part a result of extension of area in the 

 species composing them, necessitating a more or 

 less pronounced longitudinal as well as latitudinal 

 flight. Doubtless many other such minor streams 

 remain to be discovered. There can be little doubt 

 that a similar stream sets in from Central Asia and 

 flows south-east towards the coast of North China, 

 the Corea, and Japan, composed principally of hardy 

 birds of eastern origin that have extended their 

 range westwards in summer into the colder climate 

 of Siberia. The Black-throated Divers {Colymbus 

 arcticus), for instance, that breed in Eastern Asia 

 migrate east in autumn along the Amoor valley 

 and other well-recognized routes of Passage, to 

 winter in the Japan Sea. The eastern form of 

 the Common Gull {Larus camis niveus) leaves 

 its Siberian haunts at the same season, and passes 

 along very similar fly-lines to the coasts of China 



