PROBLKM 2. Hoii' Movc Coviplex Aniirmls Reproduce 



431 



Fk;. 381 Young grouse 

 batching froi/i eggs laid on 

 the ground. How will the 

 feathers look when the birds 

 are a few hours older? 

 (frank gehr) 



Fig. 382 Pelican feeding its 

 yoting. In what respects is 

 the young bird undevel- 

 oped? Compare it with the 

 parent bird. The birds at 

 the extreme left are gulls. 



(AMERICAN MUSEUM OF NAT- 

 URAL history) 



At the end of this time the food from 

 both yolk and albumen covering has 

 been absorbed and the organs of the 

 young chick have been formed. By 

 means of its bill it cracks the shell and 

 pecks its way out into the world. De- 

 velopment of the chick can be traced 

 on stained microscope slides, in museum 

 preparations, by moving pictures, or by 

 placing a dozen or more fertilized eggs 

 in an incubator and opening one every 

 day or so. See Exercise 9. 



Instincts of young and parent birds. 

 Baby chickens, ducks, turkeys, gulls, and 



the young of some other birds need rela- 

 tively little attention from the parents. 

 They leave the t^^ fully equipped to go 

 out with the mother in search of food. 

 They are completely covered with 

 downy feathers, their muscles are well 

 developed, their sense organs perfected. 

 The young of other birds, such as the 

 songbirds and pigeons, are immature 

 when they hatch. They are completely 

 dependent on their parents' care for sev- 

 eral weeks. Newly hatched sparrows are 

 naked, their eyes are closed, and the 

 muscles of their wings and legs take days 



