208 A HISTORY OF BIRDS 



make the discovery that these white, hard bodies contained 

 very kiscious meat, and with this discovery the work of selec- 

 tion would begin. 



White eggs, at the beginning of this process of weeding out, 

 would be the dominant type. Consequently, the taste for 

 white eggs would be the first to be acquired, and their enemies 

 would pass coloured so long as white eggs were to be had ; and 

 so, in course of time, the birds which laid these would die, and 

 die without leaving offspring; while those which produced 

 blotched and spotted eggs would produce more vigorous off- 

 spring because they would escape the constant strain of laying 

 a large number of eggs in each season, and year after year, to 

 replace the loss by robbery. Such offspring would, in turn, 

 inherit the tendency from their parents, lay more and more 

 strongly coloured eggs, which more and more would tend to 

 resemble their environment, or, in other words, would become 

 protectively coloured. 



And now we come to the problem of the significance of the 

 white eggs met with to-day. If the foregoing arguments are 

 sound, then few birds laying white eggs could maintain a hold 

 on life as a species, save those which deposited their eggs in 

 holes or burrows. The exception to this sweeping rule shall be 

 considered presently. Among these troglodytes then, selection 

 has been at work eliminating any but white eggs, since colour, 

 rendering them invisible in the dark, would tend to their de- 

 struction by the sitting bird when entering the nest. 



Thus then white eggs are as much the result of selection 

 as coloured. Birds, in short, lay white eggs to-day because they 

 lay them in holes. In a large number of birds, in all proba- 

 bility, none but white eggs have ever been laid since their race 

 began, while in other cases, as we shall see, this whiteness has 

 been secondarily or re-acquired. This view, however, is quite 

 at variance with that generally adopted, which was first pro- 

 pounded by Dr. Alfred Russel Wallace. This being so, it 

 would be well to state his views. He contends then that birds 

 whose eggs are white resort to holes wherein to hide them. 

 Such, for example, are the Petrels, Kingfishers, Bee-eaters, 

 Parrots, Woodpeckers, Hornbills, Hoopes, Trogons and Owls. 

 But surely the more reasonable interpretation of this rule is 

 exactly the opposite of that suggested by Wallace. That is to 



