86 



THE WINTER FOOD OF THE CHICKADEE 



ices beside the buds of deciduous trees and shrubs, and so it 

 must commonly happen that bud scales are pecked away and 

 swallowed with the eggs. 



This destruction of the myriad eggs of plant- 

 lice which infest fruit, shade, and forest trees is 

 probably the most important service which the 

 chickadee renders during its winter residence. As 

 indicated in the record below, more than 450 eggs 

 sometimes occur as the food of one bird in a sin- 

 gle day. On the supposition that one hundred 

 were eaten daily by each of a flock of ten chicka- 

 dees, there would be destroyed 1,000 a day, or 100,- 

 000 during the days of winter, a number which I 

 believe to be far below the real condition, could 

 we determine it precisely. 



The most remarkable fact regarding the life his- 

 tory of plant-lice is their power of multiplication. 

 Each egg hatches in spring into what is known as 

 a viviparous female aphid, that is, a form which 

 gives birth to living young by a process similar 

 to the method of reproduction in some of the low- 

 est animals, known as budding. This process 

 begins about two weeks after hatching, each aphid 

 giving birth to a large number of young, that in 

 turn soon become mature and give birth to others.' 

 Consequently multiplication goes on in a constantly 

 Fig. 2. Plant increasing geometrical ratio, that leads to the pro- 

 Lice Eggs on ^.|^(,^jQj^ Qf enormous numbers of the pests. Were 



Twig of Birch 



(Theseegcrs are it not for the numerous checks upon these insects 

 eaten by Chicka- found under natural conditions, they would overrun 

 ^^^■-^ plants everywhere and render agriculture futile. 



In the window-garden and the greenhouse, where these checks 

 are not always at work, the aphides often destroy plants un- 

 less some artificial remedy is employed against them. Even 

 on crops out of doors the injury due to their presence is 

 frequently great, and were it not for the destruction of their 

 eggs by chickadees and other enemies, there can be no doubt 

 that the damage would be vastly greater. 



