SAND DUNES AND SALT MARSHES 



well taken care of by Ms excited parents. It 

 is probable that many a passerine bird, nest- 

 ing over the water, has been thus saved from 

 destruction by this return to primitive meth- 

 ods. 



Further experimentation showed me that 

 very young birds generally moved the wings 

 alternately, while older ones always flapped 

 both wings together as in flight. From this 

 one would infer that the primitive reptilian 

 scramble was naturally an alternate method, 

 while the simultaneous method was simply 

 the more advanced style used in flight. And 

 this leads me to speak of the chimney swifts, 

 whose method of flight is, I am convinced 

 from frequent and long observation, an alter- 

 nate flapping of the wings. Let any one watch 

 carefully these curious birds as they dart with 

 amazing speed through the air, and I am sure 

 that he will agree with me that the wings are 

 used alternately with great rapidity. Steady 

 flight by this method is, I believe, mechanic- 

 ally possible. One might argue, therefore, 

 that the swifts retained the more primitive 

 or reptilian method of moving the front limbs, 

 and are therefore members of a very early 

 branch on the avian tree. 



284 



