33 A giant of beauty and grandeur 



likewise occur on all other continents except in South America. In 

 North America, besides the whooping crane, we also have the 

 more abundant sandhill cranes, which are divided into one species 

 and three geographic races. 



The heyday of the larger cranes appears to have been the Pleis- 

 tocene, conditions having been more favorable for their existence 

 then, perhaps, than at any time since. From what we know of 

 these conditions it seems likely, however, that the whooping 

 crane entered upon what we term "recent" time say a mere one 

 million years ago in lesser numbers than was good for them. 

 The reasons for this are forever hidden in the darkness of the pre- 

 historic past, but certain clues remain. We picture the salt seas as 

 the birthplace of all organic life; and in the endless struggle to- 

 ward perfection and improvement that is the motivating force 

 throughout the animal kingdom, we can see abundant evidence 

 that most living animals have escaped from their lowly origin in 

 the sea and found the means for development and fulfillment on 

 the land. Even today there are countless creatures still struggling 

 to make good this escape first from a marine environment to a 

 brackish- or fresh-water existence, then the final and more difficult 

 advance, from water to the land. 



Nature is dynamic, and the evolution of an organism, in very 

 general terms, may be described as a constant adaptation to 

 change. When, for example, a certain environmental condition 

 alters so that an organism is unable to secure its habitual food in 

 the usual way, it must broaden the scope of its food preferences or 

 find a new way of securing the food it is used to eating. Otherwise 

 it will perish. It is evident that the ancestors of the cranes were 

 marsh dwellers, denizens of fresh-water or brackish marshes whose 

 inhabitants were one step removed from the sea of their ancestry. 

 As conditions changed, most of the cranes moved more and more 

 into the uplands and in time were land birds for more of their 

 life than they were water birds. The sandhill cranes, which are far 

 more abundant than the whoopers, are an example. The whooper, 

 for reasons of its own, has been less adaptable, more resistant to 

 change, and not only continues to spend nearly all of its life in 

 the marshes of its progenitors, but spends one half of the year 



