242 BIRD LIFE 



' It is,' writes Mr. Py croft in his Story of Bird Life ' 

 a wonderful shilling's-worth 'almost certain that 

 originally all birds laid white eggs, as do their cousins 

 germane the reptiles. But as there is at least one 

 reptile in which there is a distinct tendency to produce 

 a coloured, rust-spotted shell, viz. the Tautera Lizard 

 of New Zealand, so there may have been many birds in 

 which the same tendency developed itself. Of these 

 many would produce eggs much more strongly marked 

 or spotted than their neighbours.' If a number of such 

 birds migrated, say, from the forest-lands of their 

 ancestors to the plains or meadows, a process of 

 weeding-out would quickly begin. For they would 

 probably at once come in contact with new creatures, 

 who would rapidly discover how good eggs were. 

 Thus those which were even slightly coloured would 

 be in so far disguised. Having a taste for white eggs, 

 their enemies would pass the coloured so long as white 

 were to be had. In this way white eggs would become 

 more and more rare, for in course of time the birds 

 which produced these would die, and die without leav- 

 ing offspring, or so few that they would be swamped by 

 inter-crossing with the newer and more vigorous race 

 who had succeeded in laying coloured eggs.' 



The same process would go on the nearer the ap- 

 proach of the colour to its surroundings, the larger the 

 proportion escaping detection until in the process of 

 the centuries such perfect imitations as the eggs of the 

 Dotterel and Snipe would result, and survive as the 

 abiding 



