PREFACE. 



There is no branch of Ornithology more popular 

 than that which treats of the Migration of Birds. 

 To the genuine lover of birds there is no more 

 fascinating pursuit than to watch the comings and 

 the goings of his favourites ; to the more scientific 

 ornithologist Migration is not only an intensely 

 interesting proceeding in itself, but a function 

 fraught with importance in the History of Avian 

 Life. In many instances it is an indicating medium 

 of affinities, an explanation of various apparent 

 anonialies in geographical distribution, and un- 

 questionably an evidence of those vast physical 

 changes which have been one of the dominating 

 features of our planet's history in past ages. 



Notwithstanding the immense popularity and 

 importance of Migration, strange as it may seem, 

 no work has hitherto been devoted expressly to 

 its discussion, A very large amount of material 



