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- 
