VALUB OF BIBBS TO MAN. 79 



Enough is known, however, to show that they have some 

 beneficial habits, as well as some injurious ones ; but they 

 constitute a very potential force for harm, on account of their 

 great fecundity. I do not know how many young our com- 

 mon species can produce in a year, but two female European 

 field mice kept in captivity gave birth to thirty-six young 

 within five months. The tally was ended by the escape of 

 one of the pair, else there probably would have been re- 

 corded a still larger number. The interval between the birth 

 of one litter of young and that of the next was only from 

 twenty-four to twenty-nine days. This shows the danger 

 that might easily arise from the unchecked increase of a 

 creature which, feeding upon both crops and trees, is capable 

 of unmeasured devastation. It also shows the folly of ex- 

 tirpating those Hawks and Owls which are known to feed 

 largely on field mice, for they constitute the only natural 

 force, that can quickly assemble at a threatened point, for 

 the reduction of these pests. 



The number of small rodents eaten by the rapacious birds 

 is almost as remarkable in proportion to their size as is the 

 number of insects taken by smaller birds. Lord Lilford says 

 that he has seen a pair of Barn Owls bring food to their 

 young no less than seventeen times within half an hour, 

 and that he has fed nine mice in succession to a young Barn 

 Owl two-thirds grown. ^ During the summer of 1890 a pair 

 of Barn Owls occupied a tower of the Smithsonian building 

 at Washington. It is the habit of Owls to regurgitate the 

 indigestible portions of their food. Dr. A. K. Fisher found 

 the floor strewn with pellets of bones and fur which these 

 birds and their young had thrown up. An examination of 

 two hundred of the pellets gave a total of four hundred and 

 fifty-four skulls : two hundred and twenty-five of these were 

 meadow mice ; two, pine mice ; one hundred and seventy- 

 nine, house mice ; twenty, rats ; six, jumping mice ; twenty, 

 shrews ; one, a star-nosed mole ; and one, a Vesper Spar- 

 row.^ In my examinations of the stomachs and pellets of 



> An article on the Barn Owl, ty W. B. Tegetmeier. Field, Vol. LXXV, 

 No. 1956, June 21, 1890, p. 906. 



' The Hawks and Owls of the XTnited States, by Dr. A. K. Fisher. United 

 States Department of Agriculture, 1893. 



