232 THE MIGRATION OF BIRDS. 



autumn in the Northern Hemisphere, yet these 

 southern and eastern birds occur at that season, 

 say in Heligoland or the British Islands, far to the 

 north of any localities they may visit in summer in 

 South-western Europe. In addition to this evidence, 

 we have also the important fact that in cases where 

 a species is composed of two races, an eastern one 

 and a south-western one, the individuals that reach 

 us generally belong to the former race ; whilst on 

 Hehgoland the total number of stragglers from the 

 south-east of Europe is far more than from the 

 south-west of that continent. There are, for 

 instance, two races of the Black-throated Chat, viz. 

 Saxicola stapazina^ an inhabitant of the extreme 

 west of the Mediterranean basin, and Saxicola 

 stapaz'ina melanoleuca, an inhabitant of the extreme 

 east of that basin, Asia Minor, and Persia. An 

 example of the eastern race has been shot in the 

 British Islands in October. Again, individuals 

 belonging to such thoroughly eastern species as 

 the Isabelline Chat {Saxicola isabellina), Richards' 

 Pipit [Anthus richardi), the White-winged Lark 

 {Alauda sibirica), the Black Lark [Akiuda tartaricci)^ 

 and Macqueen's Bustard (Otis macqueen'i)^ are 

 occasionally brought on this western stream of 

 migration, not only to various parts of western 

 continental Europe, but to Heligoland and the 

 British Islands. None of these birds are migrants 

 to Africa ; their winter quarters are in South 

 Turkestan, India, Burma, and South China, but 

 stray individuals take the wrong direction in autumn 



