112 BRITISH BIRDS. [vol. vii. 



of eggs is beyond belief ; indeed, I have known a Rook's 

 eggs to disappear one by one, and there appeared to be 

 little doubt that this individual was not a close sitter, 

 and therefore advantage was taken of the fact by the 

 occupants of adjacent nests. It can clearly be seen, 

 therefore, that the habit of incubating from the first 

 egg, is of the greatest possible value to the species, in 

 aiding the birds to rear more than a single young one. 

 But through this very habit the younger birds in every 

 family have no chance of reaching maturity : in the 

 struggle for food and existence which takes place among 

 the young in each nest of the Rook, the birds which 

 emerge from the eggs that are laid last are too heavily 

 handicapped, and after a short and pitiful life they 

 succumb to the force of circumstances. 



Taking into consideration the high development of 

 birds, there is surely in the whole animal kingdom 

 no more remarkable state of affairs ! In many forms 

 of Hfe there is a very great mortahty during the earUer 

 stages of existence : in the case of many fishes the number 

 of young w^hich perish shortly after their life has begun 

 is appalling, but these instances and others differ funda- 

 mentally from that dealt with here, for the young always 

 stand an equal chance in their struggle, whereas, in the 

 case of the birds, the later-hatched young are foredoomed 

 to perish. 



Now it is quite evident that with all the birds men- 

 tioned in the course of this paper, there is a great waste 

 of substance and energy. To commence with, the hen 

 undergoes the strain of producing the eggs, which are 

 destined to be of no use to the species. If this waste 

 did not take place, it is certain that the young produced 

 from the smaller number of eggs laid would possess 

 increased vigour, for the health and strength of the 

 female parent would be conserved instead of being 

 needlessly expended. Again, the period of incubation 

 would be shortened, and the sitting bird would be sooner 



