EXCEPTIONAL MIGRATION PHENOMEMA 115 



decidedly at variance. In the first place, a large portion of the 

 rare visitors which occur here are not young and inexperienced 

 birds, but old individuals. This is the case with the majority of 

 individuals Avhich belong to species originating from regions far 

 to the south-east and south-south-east of this island. 



Thus, in the case of the Black-headed Bunting (Emberiza 

 nielanocephala), I have obtained twelve old examples as against 

 two young summer birds ; and, in the case of the Eastern Pied Chat 

 (Saxicola morio), the Black-eared Chat (S. aurita), and the Desert 

 Chat (S. deserti), two old examples of each species as against one 

 young bird of the last-named species only. Again, almost all the 

 examples of the Rose-coloured Starlings which have occurred here 

 were old birds ; and so on. 



No more do the conditions under which such migrants make 

 their appearance admit of the conclusion that these movements 

 are merely of a roving or blundering kind, without definite plan or 

 aim. On the contrary, we are obliged to assume that these move- 

 ments, also, are ab initio dependent on definite laws or causes of a 

 recurring kind, seeing that species from different quarters of the 

 globe arrive here at correspondingly different seasons of the year, 

 each species rigidly adhering to its own particular period, viz. 

 eastern and north-eastern species in autumn, and those from the 

 south-east and south in spring. Nor do these acting causes confine 

 their influence to isolated individuals, but on the other hand assert 

 themselves to such a degree in the case of all kinds of different 

 species, that one may not rarely see together on one and the same 

 day, on this little rock, species of different genera, whose breed- 

 ing homes are situated nearly a thousand miles away in eastern 

 Asia; each species, moreover, being frequently represented by as 

 many as two or three examples. 



As I think that it may be of interest to adduce instances of this 

 nature, I may, perhaps, be allowed to quote the following extracts 

 from my journal : 



1860. June 18. Charadrius fulvits and Emberiza melanocephala. 



1861. Oct. 10. Sylvia superciliosa. Three examples together in a willow. 



1863. Oct. 9. Sylvia superciliosa and Emberiza rustica. 



1864. June 12. Sylvia (Acrocephala) agricola and S. (Euticilla) mesoleuca. 



Both new to Heligoland and Germany. 

 Oct. 4. Turclus varius and S. superciliosa. Two examples of 



the latter species. 

 1867. May 9, Emberiza ccesia and Saxicola morio. 



Sept. 19. superciliosa, two examples, and Emberiza pusilla. 

 1870. 19. Sylvia superciliosa and Emberiza rustica. 



