CHAPTER V 



THE GENERAL HABITS AND FUNCTIONS OF BIRDS 



The flight of birds — Flightless birds — The fitness of birds 

 for an aerial existence — Various modes of flight — Gliding 

 flight : how performed — Flight by active strokes of the 

 wings: how performed — The movement of the wings — 

 Soaring or sailing flight : how performed — Terrestrial 

 and aquatic motion of birds — Birds unable to progress 

 upon the ground — Running, walking, and hopping 

 movements — Progress in water — The food of birds — 

 Modifications of the bill — Common to various distantly 

 related groups — Social, gregarious, or solitary instincts 

 of birds — Mimicry in birds — Protective colours and 

 resemblances of birds — Forest birds — Desert birds — 

 Marsh and swamp birds — Moorland and mountain 

 birds — Arctic birds — Variation in birds — Of external 

 structure and colour — Dimorphism in birds — Sexual 

 dimorphism — Dimorphism independent of sex — 

 Structural dimorphism. 



We have now reached that stage in the story of 



the Birds where it becomes necessary to devote 



a chapter to their general Habits and Functions. 



We have traced their history from their early 



origin down to the present era, and briefly 



sketched their general characteristics, anatomical 



and otherwise ; we have grouped all living birds 



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