PREFACE 



The aim of this book is an ambitious one. It 

 attempts to give good evidence of the development 

 of birds from reptilian ancestors, to show what 

 modifications in their anatomy have accompanied 

 their advance to a more vigorous life, and, after ex- 

 plaining, as far as possible, their physiology, to make 

 clear the main principles of their noble accomplish- 

 ment, flight, the visible proof and expression of their 

 high vitality. After this it deals, principally, with 

 the subjects of colour and song, instinct and reason, 

 migration, and the principles of classification, and, 

 lastly, gives some hints as to the best methods of 

 studying birds. The field is a wide one. but this is 

 not in every way a drawback. Specialisation has its 

 evils as well as its advantages. Many of our best 

 ornithologists write admirably of the life and habits 

 of birds, but leave out of sight their anatomy and 

 physiology. Thus they separate things which in 

 nature are mutually dependent. The anatomists 

 and physiologists, on their side, limit themselves 

 sternly to their own departments. Their works, 



