VOL. VII.] ON INCUBATION. 113 



released from this exhausting duty. Consequently it 

 would be in a better condition to tend its young. 



When several young are hatched only to perish after 

 some days of hopeless struggle against the inevitable, 

 the parents and remaining young are penaUzed in their 

 struggle for existence, and in the following manner. 

 The old birds during the earlier period after all the 

 eggs have hatched, have to supply food for, say, five 

 nestlings. This is no light task, and there is necessity 

 for continuous labour from dawn till dark, but at least 

 two of the young fed at the expense of this strenuous 

 parental exertion are invariably, or almost invariably, 

 overwhelmed by the older members of the brood, and 

 do not come to maturity, hence the work involved 

 in feeding them is love's labour lost — the parents have 

 expended their vigour and wasted a considerable amount 

 of food to no purpose. Now, if fewer eggs had been 

 deposited and only the young hatched which would 

 eventually have a reasonable chance of being reared, 

 it would be greatly to the advantage of the individuals 

 involved, for all food brought by the parents would be 

 divided amongst vigorous offspring and these would 

 all receive a larger share than if there were more mouths 

 to be fed, therefore these- young would have a much 

 better start in the world than those reared where there 

 were young to be fed unprofitably and to some extent 

 at the expense of the older nesthngs. The adults also 

 would benefit, for they would in all probability be 

 reheved to a certain extent in their search for food, 

 and yet would easily provide a larger amount for each 

 individual of the smaller number of young. 



This being so, it is clear that a reduction in the number 

 of eggs laid would be of great value in such cases as have 

 been recorded in this article. That such reduction has 

 already taken place in many instances, there can, I 

 think, be little doubt, for the laying of a small number of 

 eggs is evidently an ornithic specialization evolved since 

 the class arose from its reptilian forerunners. 



