36 BIRD BEHAVIOUR 



selves in the animal-feeding section; though it 

 must be remembered also that a vast number of 

 insectivorous or mixed feeders have weak powers 

 of flight and very sedentary habits, such as the 

 host of small insectivorous birds resident permanently 

 in the tropics. 



The majority of birds show little or no specializa- 

 tion for the purpose of food-getting ; that is to 

 say, one very generally cannot tell from the look 

 of a bird whether it lives mainly on animal or 

 vegetable food. For instance, Pigeons, as has been 

 said above, are mainly vegetarian, and Plovers are 

 chiefly worm- and insect-eaters ; yet the bills of 

 the two groups are singularly alike, and the vege- 

 table-eating Cranes are so like the animal-feeding 

 Storks and Herons that people who are not used to 

 birds constantly confuse them with each other. 

 Similarly, it is curious that the Parrots, some of the 

 strictest vegetarians, have bills more like those of 

 the very carnivorous Hawks and Owls than like 

 those of any other birds ; and when it comes to 

 the hosts of passerine birds with the ordinary 

 unspecialized type of beak, observation alone can 

 tell what their diet is. 



There are, however, plenty of well-known and 

 conspicuous cases where structure and habit go 

 closely together ; to take a very familiar case, it is 

 easy to see that the thick, short conical bill of a 

 Finch is correlated with the habit of cracking seed- 

 husks, and the long pouch-bearing bill of a Pelican 

 is obviously especially adapted for catching fish. 



