282 ZOOLOGY 



and 1852. The second importation survived and multiplied. 

 Subsequent importations were made to Maine, Rhode 

 Island, and Pennsylvania, so that by 1870 the sparrow 

 was firmly established in the eastern United States. From 

 this time on the sparrow spread at a rate unparalleled by 

 any native bird. By 1886 it had spread as far west as 

 Kansas, and had established colonies at Salt Lake City, 



i^ 



San Francisco, and other outlying regions ; and through- 

 out this territory it occurred in great abundance. Since 

 then it has penetrated west to the Rocky Mountains, and 

 south to Texas. This extraordinary spread has been due 

 to several causes. As already suggested, the bird can 

 adapt itself to various climatic conditions, and its fecundity 

 is very great. Thus in our Southern cities there are from 

 five to six broods a year, and from four to six young in 

 each brood. Assuming that twenty-four young, half of 

 them females, are produced by a pair each year, and that 

 all the females breed when one year old, and successively 

 for ten years, and that there are no deaths, then in the 

 tenth year 138,000,000,000 individuals will have been pro- 

 duced from the original pair. To the realization of the 

 possible maximum of reproduction there are, however, 

 many checks, especially the destruction of birds by ac- 

 cidents, disease, and beasts and birds of prey. 



Food of English Sparrow. - The house-sparrow was in- 

 troduced for the purpose of destroying or holding in check 

 the wt canker-worm" and the various other caterpillars which 

 destroy our fruit, forest, and shade trees. There is much 

 doubt, however, whether the house-sparrow is at all effi- 

 cient in the way of destroying insect pests, while it is 

 quite certain that it fights with and drives away our 

 native insect-eating birds. More important still, it de- 



