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 (-jygjiQfj Qf enormous numbers of the pests. Were 



Twig of Birch ' 



(These eggs are it not for the numerous checks upon these insects 

 eaten by Chicka- fQijnd 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. 



THE WINTER FOOD OF THE CHICKADEE 



87 



On those trees whose leaves drop oft" in autumn the eggs of 

 plant-lice are commonly deposited in the crevices about the 

 buds. The eggs of the common apple aphis are indicated as 

 "black specks about the buds in Fig. i ; 

 tjiose of an abundant species on birch are 

 shown in Fig. 2; while Fig. 3 illustrates 

 the eggs of a species that lays its eggs in 

 great numbers upon the bark of willow 

 branches. Although it is impossible to 

 determine precisely the different species of 

 plant-lice from their eggs, there was rea- 

 son to believe that each of the species 

 shown in these three figures had been 

 eaten freely by the chickadees examined. 



Insect eggs of many other kinds were 

 found in the food of the chickadees. 

 Many of these it was impossible to recog- 

 nize, but there was no difficulty in iden- 

 tifying the eggs of the common American 

 Tent Caterpillar,' the egg mass of which 

 is illustrated in Fig. 4, and of the Fall 

 Canker Worm,^ the eggs of which as 

 found upon elm are represented in Fig. 5. 

 There were also present the eggs and 

 egg sacs of many spiders of kinds com- 

 monly occurring under loose bark (Fig. 

 6). While spiders as a class are doubt- 

 less beneficial creatures, the destruction 

 of some of them is not in my opinion se- 

 riously detrimental to the usefulness of the 

 chickadee. 



The larvas of several different kinds of moths were also 

 found. One of the most abundant species was believed to be 

 the common apple worm, the larva of the codling moth (Fig. 7). 

 It was difficult to be sure of the species, because the heads of 

 the larvffi were nearly always absent, but there is little doubt 



Fig. 3. Eggs of Plant- 

 lice on Baric of Willow. 

 (From a Photograph.) 



^ Clisiocamjia Americana. 

 3 Anisopteryx pomeiaria. 



