434 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1920. 



about for a place to keep it during convalescence he thought of the subcellar, 

 which was immediately fitted up with several perches. The morning after the 

 owl was placed in this cellar 9 headless rats were found, and for the next three 

 months varying numbers of headless carcasses were found daily. About this 

 time, however, the rats were becoming so scarce that the owl had to devour 

 the entire animal to secure sufficient food, and finally had to be fed on raw 

 meat. For nearly 10 years afterwards practically no damage was done by rats 

 in this cellar. 



Birds have also been successfully employed to destroy insects in 

 greenhouses. In a letter to the Biological Survey, March 27, 1893, 

 R. Bingham, of Camden, New Jersey, says : 



I am engaged in market gardening both under glass with artificial heat in 

 winter, and in the open field in summer, and until the past two years used to- 

 bacco smoke twice each week to keep in check the aphides or plant lice in our 

 plant houses. But as all insecticides while killing the insects injure the health 

 and dwarf the growth of plants, I tried the more natural, I think the more 

 economical, and certainly the pleasanter remedy, birds. First tried the indigo 

 bird (Cyanospiza cyanea) and although a seed-eater it prefers insects. Being 

 small it runs under the lettuce leaves and sometimes disappears for several 

 feet. Also have a pair of mocking birds (Mimus polyglottos) in each place. 

 One pair of mocking birds has taken care of the attic garden 20 by 28 feet. 

 One pair of mocking birds, a pair of song sparrows (Melospiza melodia), a 

 snow bunting {Plectrophenax nivalis) and a winter wren (Nannus Memalis) 

 have kept the insects in check in the larger plant house 25 by 250 feet. Have 

 had much less insect trouble, and healthier and better crops than when I 

 smoked the houses twice each week taking one hour of time for each smoking. 



The more natural and desirable use of the services of birds, of 

 course, is that made out of doors which has been done by modifying 

 farm practice to take advantage of the normal useful habits of birds, 

 by introducing birds so as to increase the number in a given area, and 

 by augmenting the bird population by bird attraction methods. 



As an example of the first class of these uses, we may cite the 

 recommendations 44 by Mr. Norman Criddle, of the Dominion Ento- 

 mological Laboratory of Manitoba, for the control of white grubs. 

 He says: 



Birds are most persistent followers of the plough during their breeding sea- 

 son or while migrating, gulls and terns from May 16 to June 22, and for a short 

 time late in July; crows and blackbirds, including grackles, from the time 

 grubs appear in May until July 1. * * * To attain the best possible results 

 ploughing should be done between May 14 and July 1, and at an average depth 

 of 5 inches. * * * Fall ploughing in Manitoba, while accounting for a few 

 pupae in September, is not a practical means of destroying white grubs. Birds 

 at that time have congregated into flocks preparatory to migrating southward 

 and are then more inhabitants of grain fields. Thus, the grubs readily make 

 their way into the ground again. 



The introduction of birds for the eradication of pests is a step 

 which should be taken only within the limits of similar faunas or 



" Agr. Gaz. Canada, vol. 5, No. 5, May, 1918, pp. 452-3. 



