INTRODUCTION xxxvii 



between their first and second broods, following the seasons of 

 flowers from the valleys where they raise their first broods, to the 

 mountain parks, where they rear a second family, retreating rapidly 

 down the mountain as soon as the frosts kill the flowers. 



Among land birds a north and south migration is not as vital in 

 the west as the east, especially for the seed-eaters, for the lowland 

 winters are so mild that the food supply is not as extensively de- 

 stroyed as in the east, and accordingly a much larger number of 

 birds winter in the valleys of the western states than in the eastern. 

 But while the western north and south migratory movement is less 

 striking, the absence of winter birds less felt than in the east, the 

 vertical migrations, from the superior height of the mountains and 

 the preponderance of the mountain ranges, assume great impor- 

 tance; and accordingly, while the total winter population may be 

 large, the species in a locality will be markedly different in summer 

 and winter. 



Careful notes should be taken on all these phases of the migratory 

 movements to ascertain the exact migratory habits of each species 

 of bird, and the character of the bird population in every season. 



As the mildness of climate which lessens the impulse to south- 

 ward migration in the western land birds does not affect the water 

 birds breeding in the arctic regions, the southward migration is 

 found in full force along the coast. At suitable points, like Mon- 

 terey, vast multitudes of birds may be seen passing on their way 

 from the arctic regions to the southern seas, and migration waves 

 and other phenomena studied to the best advantage. Mr. Loomis's 

 observations at Monterey have thrown a great deal of light on this 

 most interesting subject, and demonstrated the richness of the field 

 for future investigations. 



ECONOMIC ORNITHOLOGY. 



The question of the food of birds assumes peculiar importance in 

 the west from the extent of the fruit industry, and the consequent 

 magnitude of the depredations of insect and rodent pests. Birds if 

 left to themselves keep down the insect life, and the question is in 

 each case if the harm a bird does in eating fruit in June equals the 

 good he does the rest of the year in eating scale insects and other 

 pests that take off the profits of fruit growing. As it is a matter of 

 statistics, observers should make careful field notes on what birds 

 are actually seen eating, and especially careful records of the stom- 



