250 



BRITISH BIRDS. 



BLUE EGGS OF TERNS AND GULLS. 

 With reference to the notes on the blue eggs of Common Terns 

 and Black-headed Gulls, may I be allowed to point out that 

 in many of these varieties the surface of the egg is as glossy as 

 in the more usual types and that the shell is up to the average 

 in thickness ; also that the blue eggs are not the only con- 

 spicuous varieties ? 



NEST OF SANDWICH TERN. 

 {Photographed hy Yl. B. Dunlop), 



The Rev. F. C. R. Jourdain overlooks the fact that it is 

 from the Gulls themselves that the eggs have primarily to be 

 protected; if the birds did not sit on the eggs as soon as laid, 

 every variety at all conspicuous would immediately be taken 

 by the Gulls. 



That there is a certain amount of local variation in the 

 colouring of the eggs in different colonies is highly probable. 

 A somewhat similar case is that of the songs of some species 

 of birds, which are known to have distinct characteristics in 

 different localities. 



