CHAPTER VII 
THE ENGLISH SPARROW QUESTION 
THE multiplication of the English sparrow should 
serve as a warning to all people who would introduce 
foreign birds to this continent. If North America 
should be once more connected with Asia by a wide 
isthmus, the plant and animal life of both countries 
would be deeply affected. The Atlantic Ocean is an 
impassable barrier to most birds, and has probably 
existed as such a barrier since birds began to sing in 
the primeval forests. When we take an animal or a 
plant across this wide barrier, we introduce a disturb- 
ing factor into nature’s household on the continent 
where the species is introduced. If the new species 
finds favorable conditions, it will multiply and spread 
rapidly until it meets a new impassable barrier. The 
most remarkable illustrations are the English sparrow, 
or house sparrow in this country and the rabbit in 
Australia. : 
The house sparrow affects European song birds in 
much the same way that it influences our own. As 
far as I know, it is not claimed that it has directly 
caused a decrease of Kuropean birds. We need, there- 
fore, not be alarmed that it will cause the disappearance 
of our song birds. The enormous increase of the bird 
in this country is due to the following causes : — 
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