BIRDS 119 



return is sometimes made in great flocks that distribute 

 themselves gradually over a wide territory. Sometimes the 

 flocks are small. Sometimes the flight is direct, and some- 

 times by short and easy stages. In the spring we frequently 

 notice the appearance of flocks of robins and other species, 

 which suddenly disappear, probably having passed on farther 

 north. In a number of species the males come first. Indi- 

 vidual, marked birds have been positively known to return 

 to the same summer home year after year. 



In mild winters some of the birds of passage do not go south, 

 but remain with us. Crows, robins, flickers, song-sparrows, 

 bluebirds, etc., have been observed in the North in winter. 



There are certain birds that stay with us in the northern 

 part of the United States all the year. Owls and hawks, 

 quail and grouse, downy woodpeckers, nuthatches, chicadees, 

 bluejays, English sparrows, snowbirds, and others remain 

 with us to enliven the wintry landscape. They find a living 

 in the seeds of weeds and grasses that project above the 

 snow, or in buds, berries, and nuts on trees and shrubs. 

 The eggs, larvae, and chrysalides of insects found on the bark 

 of trees also supply a large part of the winter food. The 

 birds of prey catch smaller birds and small mammals. 



The Food of Birds 



The food of birds depends upon the species, upon the mode 

 of life of the bird, and upon the food conditions. Birds are 

 either predominantly vegetivorous or insectivorous, some eat- 

 ing the flesh of other animals. But most of the first class will 

 also eat insects, and vice versa. 



The vegetable diet consists of seeds, fruits, nuts, grains, 

 com, buds, leaves, and sap. 



