126 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



tho cost of efforts to control its ravages, is 15 million dollars. In con- 

 nection with an investigation of the bird enemies of this pest, pre- 

 liminary work was done by an assistant of the Survey in the Blue 

 Ridge apple region of Virginia. Twenty-five species of native birds 

 are known to prey upon this exceedingly destructive insect, and it is 

 believed that birds destroy from 50 to 85 per cent of the hibernating 

 pup?e. Thus they probably do more to check the increase of the 

 codling moth than all other natural enemies combined. 



MEANS OF ATTRACTING BIRDS TO ORCHARDS AND FARMS. 



The destruction by birds of the codling moth, the boll weevil, and 

 many other insect pests shows clearly not only that birds should be 

 protected, but that efforts should be made to increase their numbers 

 and so add to their efl'ectiveness as auxiliaries of the farmer. During 

 the year experiments have been initiated at the instance of the 

 Survey, with a view to testing artificial nesting sites for this purpose. 

 In Europe the use of artificial nests about houses and in orchards and 

 groves has proved a great success. They not only attract numbers of 

 birds like woodpeckers to a particular locality, where their services 

 in destroying insects are much needed, but they actually increase the 

 total number. Some such method as this is necessary in tliis country, 

 where farmers and orchardists so generally plug up cavities in trees 

 and trim off dead limbs, thus restricting the supply of nesting sites. 

 This practice is actually diminishing the number of birds, Hke wood- 

 peckers, bluebirds, and cliickadees, that nest in cavities. The 

 expenditure by the orchardist or the farmer of the small sums neces- 

 sary to supply artificial bird boxes, whether purchased or homemade, 

 will prove an exceedingly profitable investment, since it will increase 

 the total number of birds and will attract to the places where they 

 are most needed some of our most interesting and valuable species, 

 whose destruction of insect pests will repay many times the small 

 outlay made in their behalf. 



BIOLOGICAL INVESTIGATIONS. 



During the year, as usual, biological investigations covered a wide 

 field and included several States. Field work was carried on in parts 

 of Arizona, Arkansas, California, lUinois, Kentucky, Missouri, Mon- 

 tana, New Mexico, North Dakota, Oregon, Utah, and Wyoming. 

 The data gathered enabled important corrections to be made in the 

 zone map of the United States, a revised edition of which is now in 

 press. 



A report on the biological survey of Colorado is practically com- 

 pleted and will be pubHshed during the coming year. This includes 

 a map of the State showing life and crop zones, with a general dis- 

 cussion of their relations, the adaptations to different crops of the 



