ment of eggs of any bird is in exact proportion to the average danger to which 

 that species is exposed. I believe that this factor is fairly constant for species of 

 tribes of similar habits, and that exceptions indicate peculiarities of circumstances 

 which in many cases we can easily perceive, because I believe that Nature is 

 strictly economical of energy, allowing no more eggs to be laid, and consequently 

 young to be produced, than the conditions justify in each case. Thus the uni- 

 formity of avine population — the balance of bird life — is maintained. 



When a bird's nest and eggs are destroyed she will often lay another setting, 

 -and some birds raise two and even three broods in a season under normal condi- 

 tions. If the eggs of a bird are removed as fast as they are laid the bird will 

 sometimes continue to lay, one of the most remarkable instances of this in an 

 uncaged bird being a Ficker, which laid seventy-one eggs during the space of three 

 and seventy days. A tiny African Waxbill in captivity has been known to rear 

 fifty-four young in the course of a year, during the same period laying an addi- 

 tional sixty-seven eggs. The domestic hen has become a veritable egg-laying 

 machine, thanks to careful breeding in the past, since the wild Red Jungle Fowl, 

 from which all varieties of poultry are descended, lays only one nestful of seven 

 to twelve eggs once a year. 



Many birds still hold to the old style of nesting in hollow trees and such 

 concealed places. Whether they hunt around until they find a cavity ready-made 

 by the elements, or whether, like the woodpeckers, they proceed to excavate a 

 home in a dead branch, or, kingfisher-like, to tunnel deep into a sand bank, their 

 eggs are almost invariably white. Many indeed have such glossy, highly polished 

 shells that, were they laid in exposed situations, their shining surface would be a 

 sure guide to hungry egg-eaters. 



Among such birds may be mentioned the owls, woodpeckers and parrots, 

 trogons, motmots, kingfishers and pufiins, besides many others which hide their 

 eggs in domed nests. On the other hand, we find a number of birds laying spotted 

 eggs in concealed nests, and white eggs in open places ; so that no universal law 

 can be framed to account for the varied coloring. This is not surprising when we 

 think of the great difiference of conditions under which each species lives. Take 

 for example the two species of marsh wrens, which live so happily among the 

 reeds of the marshes of our Eastern States. Both birds build globular mouse-like 

 nests, both hide their treasures deep in the interior, but the eggs of the long-billed 

 species are dark chocolate brown, while the short-bill's eggs are like pearls. We 

 do not know why this difference exists, but that need not deter us from accepting 

 the facts to which the majority of eggs seem to point — that eggs which are con- 

 cealed, having no need for coloring, are white like those of reptiles. If, as many 

 writers have suggested, the colors of eggs are only meaningless by-products, there 

 is no reason why these hues should not run riot upon each egg or nestful of eggs, 

 as is the case in one or two interesting isolated cases to be mentioned shortly. 



Perhaps the most marked exceptions to the theory of the protective coloration 

 of eggs is to be found in doves and pigeons, which lay white eggs in open nests ; 



670 



