WHY DO ANIMALS BECOME EXTINCT? 231 



such havoc with the blue-birds, while in the 

 vicinity of Washington, D. C, the fish-crows 

 died by hundreds, if not by thousands. 



Fishes may also be exterminated over large 

 areas by outbursts of poisonous gases from 

 submarine volcanoes, or more rarely by some 

 vast lava flood pouring into the sea and actually 

 cooking all living beings in the vicinity. And 

 in the past these outbreaks took place on a 

 much larger scale than now, and naturally 

 wrought more widespread destruction. 



A recent instance of local extermination is 

 the total destruction of a humming-bird, Bcl- 

 loiia ornata, peculiar to the island of St. Vin- 

 cent, by the West Indian hurricane of 1898, 

 but this is naturally extirpation on a very small 

 scale. 



Still, the problems of nature are so involved 

 that while local destruction is ordinarily of 

 little importance, or temporary in its effects, it 

 may lead to the annihilation of a species by 

 breaking a race of animals into isolated groups, 

 thereby leading to inbreeding and slow decline. 

 The European bison, now confined to a part of 

 Lithuania and a portion of the Caucasus, seems 



