INDIVIDUALITY IN BIRDS. 233 



markings of a kind to suggest at once a common 

 ancestor to both cedar bird and Bohemian wax- 

 wing. Differentiation increased the white plum- 

 age in the Bohemians, and allowed it to disap- 

 pear in the cedar birds. 



So sharp are the distinguishing lines of color 

 between desert races of birds and mammals and 

 races living amid verdure that it is natural to 

 surmise that habits and conduct may also be con- 

 siderably modified by arid surroundings. Taken 

 as a great group, birds which live upon the sea 

 are certainly very different from typical forest 

 birds. Sea birds' voices, when they use them, 

 are harsh and shrill, and they can scarcely be 

 said to have a suggestion of song in their vocal 

 performances. Nearly all land birds have music 

 in their natures. If they cannot sing, they at 

 least try to play. The grouse, the woodpeckers, 

 the snipe, the woodcock, the bittern, are all in- 

 strumentalists. Land birds which sing, like the 

 thrushes, the purple finch, fox sparrow, ruby- 

 crowned kinglet, orchard oriole, water tlirush, 

 and other brilliant performers, are well known 

 to vary in the individual success of their efforts. 

 Now and then I hear a song sparrow or a hermit 

 thrush which sings so much better than its fel- 

 lows that I return to it day after day, to listen 

 to it as to a Nilsson or a Scalchi. 



If I, with didl human ears, can detect the dif- 



