34 EXTERNAL PARTS 



and the next two or three pairs successively shorter and 

 the rest successively longer, a doubly forked tail is the result. 

 This variety, though common among sandpipers, is so slight a 



forking that doubly emargiiiate'^ would be a better 



term. 



In examining a tail to discover to which type it 



belongs, the student should be careful to spread the 

 feathers but little. An emarginate tail might readily be made 

 to appear square or even rounded by widely spreading it, and 

 a truncate tail would always be changed to a rounded one. 



The upper and lower tail coverts consist of numerous short 

 feathers, and are never wanting, though the upper ones are 

 often very short, as in the ruddy duck, and sometimes very 

 long, as in the peacock, where the upper coverts, and not the 

 rectrices, form the gorgeous tail of the male bird. In some 

 of the storks the under coverts form the elegant plumes. The 

 under tail coverts form the crissum of a bird. 



CHAPTER VII 



VOICE, MOVEMENT, AND MIGRATION 



The sounds made by birds are so peculiar, and so different 

 from those that can be represented by letters, that any attempt 

 to form such sounds into words is sure to prove more or less 

 of a failure. The only successful way to learn a bird by its 

 notes, is to see the bird while hearing it. Afterwards the 

 sounds will reveal the bird. Beginners can hardly appre- 

 ciate the variety of notes a single bird can make. Some 

 have thought the only noises a catbird makes are those made 

 when disturbed. The fine songs of birds are always made 

 when undisturbed. Birds sing different c'Ongs at different 

 seasons, but the finest of all are those made during the nest- 

 ing time. A number of birds that seem to have no vocal 

 powers during the greater part the year, sing sweetly in the 



