BIRDS AND BIRD LIFE 19 



Reproduction. — Birds reproduce by means of eggs. The 

 egg not only contains the germ which develops into the 

 young bird, but contains the nourishment for the germ 

 during its development. The shell is a protective envelope 

 which guards the embryo, or young chick, during its develop- 

 ment. The bird's eggs are laid in nests, and are hatched out 

 by the application of heat from the bird's body. Birds 

 vary greatly in their nesting habits; some build nests in 

 trees and bushes, and others burrow in the ground. Some of 

 our wild birds build hanging nests. Many birds build their 

 nests directly on the ground. Others bore holes in dead 

 stumps and trees. It is a most interesting study to watch 

 the nesting of wild birds. The student can locate the nest, 

 watch its building, and the rearing of the young. Neither 

 the nest nor the young should ever be disturbed. 



Classification of Birds. — Birds are divided into three groups, 

 according to their habits of life. The first group is called 

 aquatic birds, and comprises those birds which spend a 

 great part of their time on or near the water. Common 

 domestic examples are ducks and geese. The pelican is one 

 of the wild species. The second group into which birds are 

 divided is the terrestrial, so called because these birds 

 spend a great part of their time on land. Common examples 

 of this type are the domestic fowl, quail, pheasant, etc. 

 The third group is commonly called aerial. These birds 

 derive this name from the fact that they perch largely 

 in trees and elevated places, and spend considerable of their 

 time in flying. Common examples of this type are the 

 sparrow, crow, and the swallow. 



Aquatic Birds. — All aquatic birds are primarily built for 

 swimming. The body is shallow and wide, with a flattened 

 keel, and is covered with close, compact feathers and down. 

 Birds of this group have very short legs, and are usually 

 provided with a web between the toes. The wings are, as 

 a rule, very powerful. The duck is a common example of 



