BIRD GENEALOGY 



If this prone method of propulsion on the 

 water on all fours is a primitive one, as indeed 

 it must be, then birds that swim in an erect 

 duck-like manner must have advanced beyond 

 this stage and become specialized. I have sev- 

 eral times seen young spotted sandpipers that 

 w^ere unable to fly, swim with ease like little 

 ducks, although when very young and much 

 frightened they return to the primitive rep- 

 tilian scramble on all fours. All of the mem- 

 bers of the shore-bird family, the sandpipers 

 and plovers, swim naturally if they find them- 

 selves in water beyond their depths. The 

 phalaropes, members of this family, disport 

 themselves on the surface of the water as 

 gracefully as miniature swans. It would seem 

 to be a natural inference, therefore, that the 

 ancestors of shore-birds were swimming birds, 

 and that the art of swimming was inherited 

 and not developed by this group, and that the 

 phalarope was a case of reversion. The action 

 of the young seal described in a previous 

 chapter illustrates a case where the art of 

 swimming was recently acquired by the group, 

 and not of long inheritance. 



In the classification of birds proposed by 

 Dr. Hans Gadow and generally adopted at the 



285 



