PREFACE 



The present volume is the result of much additional 

 thought and hard work generally upon the subject of 

 Avian Emigration and Migration. It is a subject that 

 has a peculiar fascination for me, doubtless because it 

 offers all the charm of novelty, and is as yet a practically 

 unworked field of research. No branch of Ornithology 

 can possibly be more interesting than that which treats 

 of the Dispersal — either by Emigration or Migration — 

 of Birds over the globe. 



To many naturalists this dispersal may appear 

 entirely fortuitous, or very largely due to such abnormal 

 influences as Glacial Epochs. I honestly confess that 

 for many years I was imbued with very similar ideas — 

 what all men accepted as true must assuredly have been 

 truth. But after a long and careful study of the phe- 

 nomenon of Emigration (or Range Extension) I began 

 to doubt some of the most generally accepted views 

 respecting the Geographical Distribution of Species. 

 Difficulty after difficulty arose, convincing me more and 

 more that the solution of the problem must be sought 

 in other directions. After much hard work at the 



