CHAPTER III 



The nutrition of birds — Various kinds of food, animal and vege- 

 table — Methods of and adaptations for obtaining it — Changes 

 of diet — Gluttony of some species — Power of discrimination 

 among foods, both vegetable and animal — The much-discussed 

 relations of birds to insects, especially butterflies. 



" Worms and flies," mentioned by Shakespeare in 

 Macbeth as the food of birds, are certainly the 

 staple of the large majority of the class, at any 

 rate if we take both terms in the wide old-fashioned 

 sense, in which a worm meant anything long- 

 shaped, and a fly almost any flying insect ; for on 

 small invertebrate life birds mostly depend, and 

 even when the old birds are mainly or largely vege- 

 tarian; the young feed, or are fed by their parents, 

 on animal food in perhaps the majority of cases. 



This diet is probably ancestral, for it is at least 

 probable that the reptilian ancestors of birds were 

 largely if not mainly animal-feeders, and thus the 

 young only go back, as in so many cases in nature, 

 to the early diet of the race. But just as even 

 among the reptiles there are some mainly vegetarian 

 kinds, such as some iguanas, the land-tortoises, 

 3 " 



