WHAT IS A BIRD ? 13| 



were similarly treated, in this way the character 

 grew more and more marked till the present 

 somewhat unsightly forms came in to being. 

 The experience of many of my readers will 

 supply a dozen such instances. 



A similar process of selective breeding seems 

 to be going on around us, amongst wild animals 

 and wild plants. It has given us hare and rabbit, 

 wolf and fox, lion and tiger, and so on. These 

 are all different from what they once were ; they 

 are all modifications of some earlier form. More 

 detailed explanations of these things must be 

 sought in other and more learned treatises ; they 

 have no place here. 



This development of species and races leads us 

 to consider another very important factor in the 

 making of a bird. This we call specialisation. 



We find certain birds fitted apparently to live 

 only upon certain spots on the earth's surface 

 or upon certain food. We say these are highly 

 specialised. 



The little humming-birds afford us an admir- 

 able illustration of a specialised bird. They 

 feed by hovering on the wing, under flowers, 

 and thrusting up the beak into the long tubes to 

 get at the insects and honey. For this purpose, 

 the beak and tongue are of great length, often 

 exceeding the length of the body of the bird 

 itself. The tongue differs from that of all other 

 birds, and is tube-like in form. Now the young 

 birds, when just hatched, have tiny three-cornered 

 beaks like those of a swift. We gather from this 

 — those of us who study these things — that this 

 long beak is a new kind of beak and that, once 



