CHANGES IN THE NUMBERS OF BIRDS 117 



are certainly extinct; one species, the passenger 

 pigeon, is probably extinct; and one species, the 

 Eskimo curlew, is nearly if not already extinct. In 

 the case of three of these species it is known that 

 destruction by man was the cause of the extermina- 

 tion. Following is the list: 



Besides these, five other species of birds, for- 

 merly found in the West Indies and one species 

 found in the Bering Islands, have become extinct. 

 Little is known of their history or of the cause of 

 their extermination. 



The passenger pigeon. The passenger pigeon was 

 formerly found widely distributed in the United 

 States east of the Rocky Mountains, and in such 

 enormous numbers that it is difficult to appreciate 

 the meaning of the records which were kept by 

 men of that time. They passed in flocks which 

 darkened the sun and required hours to pass over. 



