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 River 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 are 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. 
