142 BIRD BEHAVIOUR 



reptilian custom of laying plain white eggs — or at 

 all events very faintly tinted ones. Penguins, 

 Grebes, Pigeons, Owls, Woodpeckers, Barbets, Tou- 

 cans, Bee-eaters, Rollers, Swifts, Hornbills, King- 

 fishers, and Humming-birds all lay white eggs, 

 and although most of these lay their eggs in holes, 

 a great number do not, notably all the Humming- 

 birds and nearly all the Pigeons, our common 

 Blue-rock and the Stock-Dove being quite excep- 

 tional in the family in their habit of breeding under 

 cover. The eggs of the Duck tribe also are always 

 light-coloured and unspotted if not actually white, 

 though in this case it must be admitted that the 

 birds always cover them when leaving the nest, as 

 do some of the Game-birds, like the Partridge. 

 On the whole it would seem that birds which lay 

 white eggs simply do so because they are physically 

 incapable of laying eggs of any other colour. 



With regard to the numerous spotted eggs, it 

 may be freely admitted that when laid on the bare 

 ground, as by Plovers, they are often really hard 

 to (find, and that here protective resemblance 

 probably does come into play ; but in the case of 

 the often bright-coloured and beautifully-variegated 

 eggs of passerine birds, generally deposited in open 

 nests in trees and bushes, the colour does not seem 

 to be of any great importance, the great point 

 being that the nest should be concealed. If such 

 eggs were coloured to assimilate to the foliage, we 

 might expect some green ones, but in practice 

 there are no truly leaf-green eggs except those of 



