170 BIRD WORLD. 



blances and differences, try to trace back the descent 

 of all these creatures and plants, and to discover how 

 many are descended from the same ancestor. 



When books on natural history speak of this or 

 that family of birds, the words do not mean parents 

 and their four or five children ; they mean all the 

 birds which resemble each other so closely that they 

 probably have descended from the same bird. It is 

 like a clan in Scotland, where in thousands of houses 

 you find people who belong to one great family ; they 

 are all related, and many can trace their relationship 

 to the head or chief of their clan. 



In some cases it is easy in Bird World to see the 

 relationship in a great family ; in others it is not evi- 

 dent at the first glance. The Ducks, for instance, 

 form a great family which any one could separate ; 

 their webbed feet, their bills, their peculiar shape, all 

 serve to mark them as distinct from other families 

 and related to each other. 



Parrots form another large and easily defined family. 

 Owls resemble each other all over the world. In the 

 Flycatcher family and the Sparrow family the resem- 

 blance is not so easily seen, but close examination 

 shows that the birds have the same style of wing, 

 that the wings and tail have the same relative length 

 or the same general shape. Colors vary more than 

 the shape of the bills, wings, and feet, so that in the 



