RAPIDITY OF INCREASE. 



29 



or farther south, to rear twenty or thirty young in the course of a year. 

 Assuming the annual product of a pair to be twenty-four young, of 

 which half are females and half males, and assuming further, for the 

 sake of computation, that all live, together with their offspring, it will 

 be seen that in ten years the progeny of a single pair would be 275,710,- 

 983,G98. This will appear in detail from the following table: 



Annual increase and total number of English Sparrows, the progeny of a single pair, in 



successive seasons for ten years, assuming that all lived. 



Years. 



dumber of pairs 

 broediii"-. 



Number of pairs 



of young. 



Total number of 

 pairs. 



Total number 

 of birds. 



First . . . 

 Second. 

 Third.. 

 Fourth . 

 Fifth .. 

 Sixth .. 

 Seventh 

 Eighth.. 

 Ninth... 

 Tenth .. 



] 



13 

 169 



2,197 



28, 561 



371,293 



4, 826, 809 



62,748,517 



815, 730, 721 



10, 604, 499, 373 



12 

 156 



2,028 



26, 3G4 



342, 732 



4, 455, 516 



57, 921, 708 



754, 982, 204 



9, 788, 7C8, 652 



127, 253, 992, 476 



G2 



815 



10,604 



137, 858 



13 

 169 



2,197 

 28, 561 

 371,293 

 826, 809 

 748, 517 

 730, 721 

 499, 373 

 491, 849 



20 



338 



4,394 



57, 122 



742, 58(5 



9,653,618 



125, 497, 034 



631,461,442 



208,998,746 



716,983,698 



Of course, the actual increase of the Sparrow is but a small fraction 

 of the total shown in this table, which is based on assumptions, some 

 of which at least are not likely ever to be realized. But if we reduce 

 the annual number of young per pair to twelve, still assuming that half 

 are males and half females, and allow that all live even five years, we 

 shall have as the total increase of one pair in that time 33,614 birds. 

 In some cases it would seem as if these figures had actually been reached, 

 so rapid has been the increase at certain places, but it is probable that 

 in almost all cases the original stock in any town consists of several 

 pairs, and these are usually increased from time to time by accessions 

 from neighboring cities. It seems probable that the large colonies at 

 Galveston, Tex., Salt Lake City, Utah, and San Francisco, Cal., have 

 resulted wholly or in very large part from the few pairs originally in 

 troduced at those places, but it is impossible to say this of most other 

 centers of abundance. 



The following examples of evidence will serve to give a slight idea of 

 the rapidity with which the Sparrow increases. 



From Norwood Giles, of Wilmington, ST. C.: 



They rear four broods here. They began nesting as early as Januaiy 22 this year. 

 (November 13, 1886.) 



From H. B. Bailey, of East Orange, N. J.: 



It rears five or six broods yearly, with four to six young in a brood. (February 7, 



1884.) 



From Thomas Chalmers, of Holyoke, Mass.: 



It usually rears five broods annually, and five birds to a brood. I Lave known of 

 six broods in a'season from one pair cf birds. Its fecundity is astonishing ; the num- 

 ber of eggs that can be taken from a mature female is something incredible. (March 

 6, 1884.) 



