CHAPTER 11. 



GENERAL STRUCTURE AND FUNCTIONS OF BIRDS. 

 THE HEAD. 



The head of birds is in general small in pro- 

 portion to the whole animal ; and the jaws are pro- 

 duced and terminate in horny mandibles, which are 

 placed horizontally, forming the bill ; which, except- 

 ing in those species that kill prey, is the chief or the 

 sole instrument in feeding. The bill varies much, 

 both in the form and in the consistency of the man- 

 dibles. In some it serves as a pair of strong pincers 

 for tearing flesh; in others it is a spear for transfixing ; 

 in others again it is adapted for hewing into timber ; 

 or it is fitted for boring into the ground or for dabbling 

 in the sludge at the bottom of shallow w^aters, in which 

 cases it is understood to have a sentient covering, so 

 that it can both find and seize the food. Sometimes 

 it is borne open as the bird flies, and catches insects 

 as in a net ; in other cases it catches by snapping. 

 In some it is fitted for breaking the hard shells of 

 fruits ; in others for cleaving pulpy ones, or raising 

 the scales of cones so as to get at the seeds. The 

 modes of using it are indeed exceedingly varied ; for 

 birds are almost universal feeders, both in regard of 

 substance and of situation ; and wherever a bird's 

 food is to be found, there is generally a bird to eat it, 

 and the bill of that bird is always very well adapted 

 for taking it. But the office of the bill ends with the 



