44^ The Bird 



eggs in domed nests. On the other hand we find a num- 

 ber of birds laying spotted eggs in concealed nests, and 

 white eggs in open places; so that no universal law can 

 be framed to account for the varied colouring. This is 

 not surprising when we think of the great difference of 

 conditions under which each species lives. Take for ex- 

 ample the two species of marsh wrens which live so happily 

 among the reeds of the marshes of our Eastern States. 

 Both birds build globular mouse-like nests, both hide their 

 treasures deep in the interior, but the eggs of the Long- 

 billed species are dark chocolate-brown, while the Short- 

 bill's eggs are like pearls. We do not know why this 

 difference exists, but that need not deter us from accept- 

 ing the facts to which the majority of eggs seem to point: 

 that eggs which are concealed, having no need for colour- 

 ing, are white like those of reptiles. If, as many writers 

 have suggested, the colours of eggs are only meaningless 

 by-products, there is no reason why these hues should 

 not run riot upon each egg or nestful of eggs, as is the 

 case in one or two interesting isolated cases to be men- 

 tioned shortly. 



Perhaps the most marked exceptions to the theory 

 of the protective coloration of eggs is to be found in 

 doves and pigeons, which lay white eggs in open nests 

 (Fig. 349) ; with the exception, curiously enough, of the 

 Rock Dove, the wild progenitor of our domestic birds, 

 which places its nest in inaccessible caverns in the face of 

 cliffs. The almost total extermination of the Passenger 

 Pigeon has been instanced as an example of a "mistake" 

 of Nature in allotting to it white eggs; the absurdity of 



