300 



The Bird 



that the conspicuous white of the under surface of the 

 second bird is, when normally lighted up by the sun, 

 neutralized by the shadow of the bird, and the darker 

 upper parts are softened and toned down by the strong 

 direct light; while if the entire bird be unshaded, although 



Fig. 238. — Sooty Tern on her nest. 



coloured like the environment, the dark shadow beneath 

 will reveal it clearly. 



Whether or not birds really appreciate the value of 

 the protective colour of their plumage, it is certain that 

 a quail or ptarmigan will remain crouching on a brown 

 bit of turf, imtil all hope of evading danger is gone; while 

 birds w'hich are very evidently not protectively coloured 

 are invariably more wary and difficult of approach. When 



