BIRDS IN GENERAL. 



95 



has been made. This is called the nictitating or 

 winking membrane, and is in the form of a half- 

 transparent curtain, which the bird can at pleasure 

 draw over the eye, just in the same way as we use 

 our eyelids. 



The bill or beak of birds serves all the purposes 

 of teeth. It is used for seizing and bruising their 

 food, and as a sort of hand for carrying ; and is 

 besides the instrument for cleaning and pruning 

 their feathers, for building their nests, for defence, 

 and in some instances, as in that of the parrot, for 

 climbing. 



Questions. 



In what way do birds produce their young ? 

 What are they called in consequence 

 What parts are common to all birds ? 

 W r hat birds are found plentifully in hot countries? 

 What kind of birds are plentiful in cold countries? 

 How is this accounted for ? 

 Are birds numerous in temperate climates ? 

 Mention some instances of the quickness of sight in birds. 

 What guards their eyes ? 

 For what purposes is the bill useful ? 



Fish-hawk and Eagle. 



