Structure and Flight 



great length, and glands to keep it well covered 

 with a sticky substance, which prevents the escape 

 of any insect with which it comes into contact. 

 Those who have watched a Green Woodpecker 

 enjoying himself at an ant-hill will admit how 

 effective such a provision is. 



The body, too, is splendidly fitted for climbing 

 in search of food. The legs are short and power- 

 ful and the toes are arranged in a manner not less 

 striking than convenient. Two point forwards 

 and two back. The tail, moreover, is composed 

 of stiff feathers which are pressed against the tree 

 and form an additional support to the climber. 



Even more wonderful, perhaps, are the delicate 

 contrivances by which the sight of birds is regu- 

 lated. Most of us have often seen a Kestrel 

 hovering over a field searching for mice and then 

 swooping down like an arrow on its prey, but how 

 often do we realise that his eyesight changes 

 during the swift transit ? From being telescopic 

 it becomes microscopic, and without the change 

 the bird would dash itself on the ground. Yet 

 this regulation, so important for the bird's pre- 

 servation, is accomplished merely by the relaxation 

 of certain muscles attached to bony plates at the 

 back of the eyeball. While the bird is hovering 

 at some height above the ground these plates are 

 pressed against the eye, causing it to become more 

 convex, in other words, making the sight tele- 

 scopic. When nearing the ground such sight 



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