EGGS OF BIRDS. 



167 



quantity of the albumen, is brought forth in the form of a single egg-, 

 of an extraordinary size. From these it is possible that twins are pro- 

 duced, but more frequently deformities, which are seldom hatched. 



Colours of Eggs. — * It was a notion of Darwin's that the variety 

 in the colours of eggs, as well as in the colours of many animals, is 

 adapted to the purposes of concealment from their natural enemies. 

 Thus, he remarks that the eggs of the hedge-chanter (Accentor modu- 

 laris) are greenish blue, as are those of magpies and crows, which are 

 seen from beneath in wicker nests, between the eye and the blue of the 

 firmament. M. Gloger, a German naturalist, has followed up this 

 singular theory into some detail, and considers it to be a remarkable 

 provision of nature, that birds whose nests are most exposed, and 

 whose eggs are most open to the view of their enemies, lay eggs of 

 which the colour is the least distinguishable from that of surrounding 

 objects, so as to deceive the eye of birds, or of other plundering animals ; 

 while birds, the eggs of which have a bright decided colour, and are 

 consequently very conspicuous, either conceal their nests in hollows, or 

 only quit their eggs during the night, or begin to sit immediately. It is 

 also to be remarked, that in the species of which the nest is open, and 

 the female brings up the brood without the assistance of the male, 

 these females are generally of a different colour from the male, less con- 

 spicuous, and more in harmony with the objects around. The fore- 

 sight of nature has, therefore, provided for the preservation of the 

 species of which the nest is altogether exposed, by imparting to the eggs 

 a colour which will not betray them at a distance ; while she could, with- 

 out inconvenience, give the brightest colour under circumstances where 

 the eggs are concealed from view. Or, perhaps, to speak more cor- 

 rectly, numerous birds can deposit their eggs in places accessible to 

 view, because the colour of the eggs makes them be confounded with 

 the surrounding objects; while other birds are obliged to conceal their 

 nests, because the conspicuous colour of the eggs would have attracted 

 their enemies. Let the explanation, however, be what it may, the fact 

 exists, and M. Gloger, who has examined all the birds of Germany, is said 

 to have satisfactorily proved it. Eggs, then, must be distributed into two 

 series, according as their colour is simple or mixed. The simple colours, 

 such as white, blue, green, yellow, are the brightest, and consequently the 

 most dangerous for the eggs. The pure white, the most treacherous of 

 colours, is found among birds which breed in hollow places, like the 

 woodpeckers, the wry-necks, the roller, the merops, the kingfisher, the 

 snow-bunting, the robin, the water-ouzel, the swallow, the martins. It 

 is only among these birds that the eggs are of a remarkable whiteness. 



