THEIR REPRODUCTION (EGGS) 297 



colour pigments that adorn those of so many 

 species at the present time. Colour appears to 

 be an after development, purely for protective 

 purposes, and in cases where it is not necessary 

 we do not find it present, or it may be in such 

 cases where we do so it is due to affinity or to 

 hereditary causes. Or it may be the inability 

 to develop it confines many species to certain 

 methods of nidification. Now in a great many 

 instances in fact so numerous are these that 

 we may lay it down as a rule where the eggs 

 are hidden from view in holes in the ground or 

 trees, or in domed or covered nests, they are 

 generally white or pale blue and without mark- 

 ings. Among such species we have the Wood- 

 peckers, Kingfishers, Parrots, most of the Owls, 

 the Rollers, Bee-Eaters, Dippers, Wrens, Titmice, 

 and so forth. In all these cases the white 

 eggs (or in some instances very sparsely spotted 

 ones) would not only be very conspicuous if 

 they were laid in open cup-shaped nests, but in 

 not a few species the sitting bird itself would be 

 rendered equally conspicuous by its brilliant or 

 showy plumage. But then it may be urged that 

 there are, on the other hand, a very considerable 

 number of species which actually do lay white 

 eggs in open and exposed nests. These apparent 



