The Body of a Bird 309 



Hawk must learn to fly still faster. If the duck learns 

 to crouch close to the reeds when his flight-feathers are 

 moulted and he is helpless, the hawk must develop 

 ever sharper eyesight. We may puzzle and puzzle over 

 a characteristic habit or a colour of some bird, finding 

 no solution, until we discover some special enemy or 

 other factor in its life which makes all clear. 



So, among aggressive colours we may mention the 

 garb of the penguin, which is steel-gray on the back and 

 silvery white below; not to protect it from danger, but 

 to enable it the better to approach fish without alarming 

 them. It is curious how fish-like the coloration of these 

 birds really is, and they are said frequently to lay feet 

 and tail together and, drawing their flipper-like wings 

 to their sides, spring clear of the water again and again, 

 by a single motion of the back muscles, exactly as the 

 mammalian dolphins leap ahead of a vessel's bow. 



Again, while we find the ptarmigan mimicking the 

 snow in colour, we find the Arctic Fox, the Snowy Owl, 

 and the Gyrfalcon, all of which are enemies of this bird, 

 also garbed in white. The ptarmigan may crouch upon 

 a drift, but it must ever be on the alert, lest from amid 

 the snowflakes a white death come suddenly upon it. 

 Nature is terribly just in her plan of life's battles. 



In the same region wdth these lives the Ivory Gull, 

 immaculate as the ice-floe over which it flies, and in its 

 whiteness w^e can perhaps read two purposes: a better 

 chance to elude the fierce Gyrfalcon, and a better chance 

 to float cloud-like unperceived over the unsuspecting fish 

 which it seeks for food. 



