136 THE MEANING OF EVOLUTION 



the time when he is in his most exquisite feather and 

 most charming mood is the time when he sings most 

 sweetly, and this is the time when he is taking to him- 

 self a mate. The love joy may so overcrowd his life 

 that he sings much and often, but the increase in its 

 amount and character during the mating season seems 

 to proclaim its purpose beyond a doubt. 



In addition to the allurements above described there 

 are certain peculiar behaviors of the animal during the 

 mating season which are intensely interesting. Some- 

 times they consist simply of a wild delirium of joy, 

 which overpowers the animal completely and makes 

 him do wonderful things. Birds will fly with impetu- 

 ous leaps in the air, mount higher and higher, singing 

 wildly, only to turn suddenly at the top of the flight 

 and drop promptly to the ground. I have seen such 

 ecstatic flights in the oven bird and in our rollicking 

 gold finch. I have seen a catbird on his way to a tree 

 turn three somersaults, much like those performed by 

 a tumbler pigeon, after which he alighted upon the 

 bough. None of these acts seemed deliberately per- 

 formed in front of the females, but I have seen three 

 or four killdeer parading in most stately and precise 

 manner, spreading their wings and fluffing their 

 feathers, performing a sublimated cup-and-cake walk 

 amid a circle of attracted females. 



Even our little English sparrow, as I have previ- 



