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 i ncreas ing geometrical ratio, that leads to the pro- 
L'ce F S& S on duction of enormous numbers of the pests. Were 
Twig of Birch . 
(These eggs are it not for the numerous checks upon these insects 
eaten by Chicka- found under natural conditions, they would overrun 
dees.) 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 then- 
eggs by chickadees and other enemies, there can be no doubt 
that the damage would be vastly greater. 
