THE DISTRIBUTION OF ANIMALS 93 



The Species of Birds 



We will now pass on to the most familiar, the most beauti- 

 ful, and the most wonderful of all living things — the birds. 

 These form one of the culminating lines of development of 

 the great world of life ; they are the most specialised of all 

 the higher animals ; and so far as perfection of organised 

 structure is concerned may be considered to hold a higher 

 place than the mammals themselves. Were they not so familiar 

 to us, we should consider it to be impossible that warm-blooded, 

 active creatures, with a bony skeleton, could have their fore- 

 limbs (or arms) so modified as to be used exclusively for 

 flight, and yet, with no organ of prehension but the mouth 

 prolonged into a beak, sometimes aided by a foot, be completely 

 adapted to obtain every kind of vegetable or animal food, to 

 protect themselves from enemies, and to construct the most 

 perfect abodes for their helpless young to be found among the 

 higher animals. 



Some zoologists consider that in the power of flight birds 

 are surpassed by insects, but I cannot think this to be the 

 case. If we take into consideration the weight they have to 

 carry, the height they often attain above the earth, their per- 

 fect command over the direction and speed of their motion, 

 and the exquisite and highly complex organ by which flight 

 is effected, birds must take the higher place. The insect's 

 flight is simpler and more automatic; that of the bird more 

 elaborate in every part, more completely under the control 

 of the creature's will. It is also, I believe, more varied in 

 exact adaptation to the mode of life of each of the species. 



As regards their variety of structure, the numbers of the 

 species, and their mode of distribution over the earth's sur- 

 face as compared with the other forms of life already con- 

 sidered, a few examples will be sufficient to prove their general 

 correspondence with other animals. It must be remembered, 

 however, that in birds the numbers inhabiting the several 

 countries are less precise and less comparable than in any other 



