SCHOOL DEPARTMENT 



Edited by A. A. ALLEN. Ph.D. 

 Address all communications relative to the work of this 

 department to the Editor, Cornell University, Ithaca, N. Y. 



STRUCTURE AND HABIT 



With Photographs by the Author 



Discussing the bird as a flying machine, we endeavored, in the last number 

 of Bird-Lore, to point out how all birds are intrinsically alike in their general 

 structure because of the physical requirements of flight. It remains for us, 

 now, to call attention to the differences in the structure of birds arising from 

 their varied habits, especially those of procuring their food. Whether the 

 differences in the form of bills and feet that are found among birds are due to 

 their different methods of securing their food, or whether it is the other way 

 around, and their method of feeding is due to the differences in the structure 

 of these parts, is a disputed point which we will not try to settle here. Suffice it 

 to say that the majority of scientists today believe that modifications of the 

 individual bird which are the direct result of its environment are not inherited 

 but that the process of 'Natural Selection' or the 'Survival of the Fittest' 

 serves to weed out those birds which do not show adaptations to their mode of 

 living, and the result is the same. That is to say, the differences in the form of 

 hill, and feet, and wings that we are familiar with today are the sum total of a 

 great many little and big variations that have been preserved through the 

 course of evolution because they were adapted or well suited to the mode of 

 life of the bird. That a beautiful adaptation between a bird's structure and its 

 mode of life docs exist, there can be no doubt, and one of the most interesting 

 studies in ornithology is the endeavor to learn the reason for each little peculiarity 

 of structure that we find in our familiar birds. 



The changes or adaptations that have occurred in the evolution of birds 

 have been for the most part gradual. This is evidenced by the fact that today 

 the birds that have arisen from common ancestors are still, for the most part, 

 more like each other than they are like other birds, in spite of their diversity 

 of habits. Were it not so it would be impossible to group birds into orders 

 and families. The fact that some birds have been more plastic than others 

 in their ada])tations and have develo{)ed parallel with unrelated birds of 

 similar iiabits, causes many of the difficulties in our present scheme of classi- 

 fication. Thus the Hawks and Owls are really very distantly related, the Owls 

 probably belonging with the Nighthawks and Whip-poor-wills, but because of 

 the Owls' camiN'orous habits, they look superflcially like the Hawks and are 

 still put with them for the sake of convenience by many American orni- 

 thologists. Herons, Kingfishers, and Terns, likewise, have bills that are much 



(I02) 



