CLASS AVES (BIRDS). 33 i 



Geese, Ducks and Swans (Anseres). These are familiar 

 birds (Fig. 136) with heavy body and characteristic form. 

 Their feet have three toes united by a web. The bills 

 are broad and have a saw-like edge for cutting. They 

 feed upon vegetation or on the smaller water animals. 

 They are interesting because of their annual migrations. 



FIG. 138. Green heron (Ardea virescens). Photo by Shufeldt. 



The ducks and geese spend the winter in the tropics 

 and nest in the colder regions. There are said to be forty 

 species of ducks, sixteen species of geese, and three species 

 of swans native to North America. 



Cranes, etc. (Paludicolce) . This group includes the 

 marsh birds, which either wade or stalk about the shallow 



