128 JOTTINGS ABOUT BIRDS. 



Now I think it is a pretty general rule 

 throughout the entire class Aves, that the number 

 oF young is regulated to a very important extent 

 by the amount of food available and the degree 

 of difficulty in obtaining it. We find that the 

 birds which produce the greatest number of 

 offspring are the various species of Game Birds 

 and the Ducks. The young of these birds are 

 reared without any great exertion on the part 

 of the parents, indeed the chicks are able in a 

 great measure to feed themselves. It would be a 

 difficult if not an impossible task for a Duck or 

 a Pheasant to bring up a score of chicks, if each 

 individual required as much attention and personally 

 administered nourishment as a young Eagle or a 

 young Robin, for instance. On the other hand, a 

 Petrel, a Guillemot, and a Puffin rear only one 

 chick at a time ; a Pigeon, an Eagle, or a Nightjar 

 produce only tw^o chicks for a brood ; the con- 

 ditions under which their young are reared being 

 such that a greater number of nestlings would run 

 serious risks of starvation, either owing to the 

 scarcity or precariousness of the food supply 

 (notably in such species as the Raptores), the 

 difficulty involved in conveying that food to the 

 nest, and, most important fact of all, the voracity of 



