CHAPTER VIII 



EGGS OF BIRDS 



In the same way that the nests of birds differ 

 in appearance and structure, according to 

 species, so do their eggs, even eggs that are 

 purely white have some specific differences ; 

 the size of the egg, its shape, the consistency 

 of the shell surface (smooth or rough) and the 

 quaUty of the whiteness, must all be taken 

 into account. Purely white eggs, as I have 

 said, are usually found in situations where 

 light does not penetrate, or else are the eggs of 

 birds whose ancestors nested in dark places, as 

 in the case of the pigeons. 



From white we come to tinted eggs uni- 

 formly coloured, graduating from very light 

 shades to intense colour, such as the pure 

 immaculate blue of the hedge-sparrow's egg. 

 The hghtest coloured eggs (not purely white) 

 are those of aquatic birds. It should be noted 

 that some of the ducks nest in the dark. The 

 common wild duck occasionally builds in the 

 hollow of a tree ; the shell-duck invariably 



49 



