SOME COMMON BIRDS 551 



south and remain until fall are called summer residents; those that 

 come south during the winter for food and to escape the severe 

 cold are called winter residents; and those that remain only a few 

 days or a week in a locality when passing to the north or south 

 are called transients. 



In Europe, where the problem of bird migration has been studied 

 carefully, migrations appear to take place along well-defined paths. 

 These paths usually follow the coast very exactly, although in 

 places they may take the line of the coast that existed in former 

 geological times. In this country the Mississippi valley forms one 

 line of migration, while the north Atlantic seacoast forms another 

 route. Just why birds migrate is not fully known. Evidently food 

 shortage in the fall starts them on the path southward, but why 

 they return is not so clear. They seem to have some instinct 

 which brings them back year after year to the same nesting places. 



Self-Testing Exercises 



Mark in your workbook the correct statements : 

 T. F. 1. Few birds are entirely useful. 



No insect pest can be entirely controlled by birds. 



Birds feed on the food that is most abundant at the time. 



Robins do more harm than good, for they eat our cherries. 



Birds of prey are scavengers. 



Most of our migrants, as the finches, warblers, and 

 swallows, feed upon harmful insects. 



T. F. 7. Most owls are harmful because they feed upon rodents. 



PROBLEM VII. HOW CAN WE RECOGNIZE SOME COMMON 



BIRDS? 



It has been estimated that during the year there are between 

 100 and 500 species of birds to be found in localities in various 

 parts of the United States. The desert regions of the Southwest 

 naturally have the fewest, the eastern seaboard states may have 

 200 to 300, while there have been about 500 species identified in 

 the northern and central parts of California. 



Field Exercise. Make a survey of your neighborhood to find out 

 the number of different birds that are residents or migrants there. 



T. F. 



2. 



T.F. 



3. 



T.F. 



4. 



T.F. 



5. 



T.F. 



6. 



