250 ANIMAL LIFE 



other times. Many fresh-water fishes, as trout, suckers, 

 etc., forsake the large streams in the spring, ascending the 

 small brooks where they can rear their young in greater 

 safety. Still others, known as anadromous fishes, feed 

 and mature in the sea, but ascend the rivers as the im- 

 pulse of reproduction grows strong. Among such species 

 are the salmon, shad, alewife, sturgeon, and striped bass in 

 American waters. The most noteworthy case of the ana- 

 dromous instinct is found in the king salmon or quinnat 

 of the Pacific coast. This great fish spawns in November. 

 In the Columbia Eiver it begins running in March and 

 April, spending the whole summer in the ascent of the 

 river without feeding. By autumn the individuals are 

 greatly changed in appearance, discolored, worn, and distort- 

 ed. On reaching the spawning beds, some of them a thou- 

 sand miles from the sea, the female deposits her eggs in 

 the gravel of some shallow brook. After they arc fertilized 

 both male and female drift tail foremost and helpless down 

 the stream, none of them ever surviving to reach the sea. 

 The same habits are found in other species of salmon of 

 the Pacific, but in most cases the individuals of other spe- 

 cies do not start so early or run so far. A few species of 

 fishes, as the eel, reverse this order, feeding in the rivers 

 and brackish creeks, dropping down to the sea to spawn. 



The migration of birds has relation to reproduction as 

 well as to changes of weather. As soon as they reach their 

 summer homes, courtship, mating, nest-building, and the 

 care of the young occupy the attention of every species. 



138. Care of the young. In the animal kingdom one of 

 the great factors in development has been the care of the 

 young. This feature is a prominent one in the specializa- 

 tion of birds and mammals. When the young are cared for 

 the percentage of loss in the struggle for life is greatly re- 

 duced, the number of births necessary to the maintenance 

 of the species is much less, and the opportunities for spe- 

 cialization in other relations of life are much greater. 



