THE TPIIRD PROBLEM OF BIRD LIFE. 



KKPKODUCTIOX AND ITS EFFFX'T UPON HABITS. 



The search for food and for safety has resulted in making 

 our plain birds over inside and outside. They are transformed 

 in structure and in color. What is there left to be done by 

 this third problem ? 



The care of a bird's young is in a great measure a repetition 

 of its care for itself. They must be fed and protected. Of 

 course it makes no difference whether the food sought is to be 

 eaten by the bird itself or to be given to its young ones; 

 whether the color-change merely protects the old bird's life 

 or her own and her nestlings'. To a very great degree the 

 cares and labors of reproduction must produce the same eifects 

 as the other two great demands of the bird's life. But does it 

 do nothing else ? Is an instinct as resistless as that of hun- 

 ger, requiring the bird's closest attention several months in 

 the year, to have no effect of its own ? No other of the bird's 

 labors is so absorbing, so exacting, so unceasing, as the care of 

 its young. It demands the bird's greatest energy, it taxes to 

 the utmost her courage, discretion, and forethought; all her 

 mind is occupied with building the nest, and afterward with 

 feeding and defending the helpless young. Shall this leave 

 no mark that can be seen ? 



Here we find the principal effect of reproduction — what we 

 call its specific effect, because it seems to belong to this prob- 

 lem more than to any of the others. The specific effect of 

 the first problem was a change of structure ; the specific effect 



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