268 



ANIMAL LIFE 



finally teaches it to fly and to hunt for food for itself. 

 Young chickens are not so helpless as the nestling robins, 

 but are able to run about, and under the guiding 



care of the hen mother to /' pick up food for 



themselves. 



Among the mam- 

 mals the young are 

 always given some 

 degree of care. Ex- 

 cepting in the case 

 of the duck-bills, the 

 lowest of the mam- 

 mals, the young are 

 born alive that is, 

 are not hatched from 

 eggs laid outside the 

 body and are nour- 

 ished after birth for 

 a shorter or longer 

 time with milk 

 drawn from the 

 body of the mother. 

 Before birth the 

 young undergoes a 

 longer or shorter 

 period of development and growth in the body of the 

 mother, being nourished by the blood of the mother. The 

 nests or homes of mammals present varying degrees of 

 elaborateness, from a simple cave-like hole in the rocks 

 or ground to the elaborately constructed villages of the 

 beavers with their dams and conical several-storied houses 

 (Fig.' 163). The wood-rat piles together sticks and twigs 

 in what seems, from the outside, a most haphazard fashion, 

 but which results in the construction of a convenient and 

 ingenious nest. The moles and pocket-gophers (Fig. 165) 

 build underground nests composed of chambers and gal- 



FIG. 162. Tailor-bird ( Orntthotornus sutorius) 

 and nest. 



