550 MAN CONTROLS HIS ENVIRONMENT FOR WEALTH 



birds showed that they had consumed over one hundred kinds 

 of weed seeds. The Biological Survey estimated that the 

 various seed-eating native sparrows saved the farmer the sum of 

 ,260,000 in 1910. The tree sparrows alone in the state of 



Iowa are estimated to eat 

 875 tons of weed seeds 

 every winter. Not all 

 birds are seed or insect 

 eaters. 



Other foods of birds. 

 Some, as the cormorants, 

 ospreys, gulls, and terns, 

 are active fishers. Near 

 large cities especially, gulls 

 act as scavengers, destroy- 

 ing much floating garbage 

 that otherwise might be 

 washed ashore to become 

 a menace to health. The 

 buzzards of the West and 

 South, and the vultures of 

 India and semi-tropical 

 countries, are of immense 

 value as scavengers. Birds 

 of prey (hawks and owls, 

 eat living mammals, in- 

 cluding many harmful 

 rodents, as gophers, field mice, and rats. The Biological Survey 

 has estimated that owls and hawks are worth about $20 apiece a 

 year to the farmer because of the field mice they eat. 



Geographical distribution and migrations. Most of us are aware 

 that some birds remain in a given region during the whole year, 

 while other birds appear with the approach of spring, and depart 

 southward with the warm weather in the fall of the year. Such 

 birds we call migrants, while those that remain in one place the 

 year round are called residents. For any one locality the migrants 

 fall into three groups : those that arrive in the spring from the 



The golden plover spends the summer in the north- 

 ern part of North America and the winter in the south. 

 Explain why it takes a different route north in the 

 spring from the one it takes south in the fall. 



