BIRDS 297 



are hollow, to give strength and lightness. Moreover, the 

 hollow spaces are often connected by tubes with the res- 

 piratory organs, by which means they may be filled with 

 air, and the buoyancy thus increased. The wings are 

 attached at the very highest part of the thorax so that the 

 weight of the body is placed below the wings, when out- 

 stretched. 



Note the penguins, in which the wings have been modi- 

 fied into organs of locomotion in the water, while the ostrich, 

 which lives on land and has no functional wings, is furnished 

 with long, strong legs for running. 



The eagles and hawks have eyes and feet wonderfully 

 adapted to their mode of hving. The owls also possess 

 eyes adapted to hunting in the night time, hence are able 

 to avoid much competition in obtaining their food. 



We can hardly study the habits and structure of any bird 

 without finding interesting adaptive modifications to its 

 environment and mode of living. This phase of the sub- 

 ject is a most entrancing and fruitful study. 



The extermination, protection, and economic value of birds. 

 — The rapidity with which the birds are being extermi- 

 nated is appalling to those who understand and appreciate 

 their value to mankind. One of the most striking instances 

 of the tremendous decrease in the number of birds is 

 shown in the case of the wild, or passenger pigeon. Alex- 

 ander Wilson saw a flock of pigeons in Kentucky in 1808, 

 that he estimated to contain 2,230,272,000 individuals. 

 Great flocks of these pigeons continued common up to 1840, 

 but now, not only the flocks but the individuals are becoming 

 comparatively rare, especially in the northern United 

 States. Birds are being lessened by hundreds by the fad for 

 egg collecting, confined chiefly to boys. They are being 



