276 BIRDS 



has three lids, an under and an upper lid and a third lid 

 that can be drawn over the whole eye, known as the nictitat- 

 ing membrane. The sparrow has no external ear, but the 

 opening to the internal ear may be seen just back of and a 

 httle below the eye. It is covered by a tuft of loose feathers. 

 The sense of hearing is keen, and birds depend upon their, 

 sense of sight and of hearing to detect their enemies. The 

 sense of touch is distributed all over the body. 



Life history of the sparrow. —The sparrow builds its 

 nest in almost any nook or cranny about the cornices of 

 buildings or among the branches of trees. The nest is a 

 simple one made of stems and twigs mixed with hair and 

 grass and lined with feathers. Six to ten eggs are laid 

 at a time and there are five or six broods in a season. 

 Sparrows multiply very rapidly, and were it not for rats, 

 mice, snakes, cats, etc., they would be much more abundant 

 than they are. They are exceedingly hardy birds and crowd 

 out other kinds. 



The sparrow's adaptation to flight. — In the first place, 

 the general form of the body is conical, thus offering as 

 Httle resistance to the air as possible. The covering of 

 feathers give buoyancy to the body and aid greatly in sus- 

 taining the weight of the animal in the air. The wings 

 are placed near the dorsal side of the body so that the 

 weight of the animal will hang suspended from the point 

 of support and lessen the hability of being overturned in 

 the air. The breastbone is furnished with a ridge, or keel, 

 and the sides are long and sloping to afford space for the 

 attachment of the powerful muscles that move the wings. 

 Moreover, the large feathers on the wings and the manner 

 in which they are arranged increase the surface of these 

 organs of flight and enable them to present additional re- 



