xvi INTRODUCTION. 



The jaws or beak are encased with a sheathing of horn, 

 except in Ducks and Flamingoes, where they are covered 

 with a soft skin, except at the extreme tip. In many 

 birds also, as in Hawks and Parrots, the basal part of 

 the bill is soft, forming what is called the cere. The 

 nostrils are usually at the point of the beak, but in some 

 birds as, in Geese, Gulls and Cranes, they are central ; 

 in the Golden-eye Ducks {Clangula) nearer the tip 

 than the root; and in the Kiwis {A'pteryx), which are 

 the only birds which go about sniffing for food like a 

 beast, they are quite at the tip. The Kiwis, by the way, 

 are not only the only birds which seem chiefly guided 

 by their sense of smell, but the only ones in which the 

 sight is deficient, for they seem to see but poorly. 



The tongue usually corresponds to the length of the 

 bill, but in some long-billed groups, as Ibises and King- 

 fishers, is remarkably short, and can be of little use. 

 In Cormorants and Pelicans it is rudimentary. Except 

 in honey-sucking birds, it can seldom be protruded far 

 out of the mouth, and it may be mentioned that in- 

 voluntary protrusion of the tongue in honey-suckers is 

 a fatal symptom. 



The eyes are generally large, and are furnished with 

 a well-developed third eyelid, or nictitating membrane, 

 a thin filmy skin which is seen sometimes to pass across 

 the eye from its interior corner. This is the way birds 

 wink, as a rule, and hence their want of expression to 

 our eyes. Owls and Moreporks, however, blink with the 

 upper eyelid like a human being, so also does the Water- 

 Ousel or Dipper. Most birds, when closing the eye, bring 

 the under lid upwards. In death the eyes are always 

 closed, birds not dying with their eyes open like beasts. 



Although birds do not possess external ears like 

 'beasts, and although the ear-opening is commonly over- 

 hung by a patch of stiff feathers, the ear-coverts, their 

 sense of hearing seems to be quite equal to that of 

 ordinary beasts. 



