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 European 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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