170 



USEFUL BIRDS. 



It will be seen from this table that the average number of 

 eggs found in the ovaries of each moth was' one hundred and 

 eighty-five. Mr. Bailey was very positive, from his contin- 

 uous field observations, that each Chickadee would devour on 

 the average thirty female cankervvorm moths per day from 

 the 20th of March to the 15th of April, whenever these in- 

 sects were plentiful. If the average number of eggs laid 

 by each female is one hundred and eighty-five* one Chick- 

 adee would thus- destroy in one day five thousand, five hun- 

 dred and fifty eggs ; and in the twenty-five days in which 

 the cankerworm moths " run " or crawl up the trees, one 

 hundred and thirty-eight thousand, seven hundred and fifty. 

 It is probable that some of the moths were not captured 

 until they had laid some of their eggs, but the Chickadees 

 found and ate most of these eggs also. When we consider, 

 further, that forty-one of these insects, distended as they 

 were with eggs, were found packed within the stomach of 

 one Chickadee, and that the digestion of the bird is so rapid 

 that its stomach was probably filled many times daily, the 

 estimate made by Mr. Bailey seems a very conservative one. 



As the frost left the ground on the first warm days of 

 spring the wingless females of the spring cankerworm moth 

 appeared in the orchard and began ascending the trees in 

 great numbers. The Chickadees commenced catching these 

 insects and eating them and their eggs. Mr. Bailey placed 

 twenty-two of the females on one tree, and in a few minutes 

 twenty of them were captured and eaten by Chickadees. As 

 a practical result of the presence of the Chickadee in that 

 orchard during the winter, there were so few eggs of the 

 cankerworm moths left in the spring that, as heretofore 



