No. 4.] BIRDS AND CATERPILLARS. 321 



pillars. As examples showing the capacity of birds' stomachs 

 for this kind of food, a few of his notes are given in brief 

 below. In most cases it was impossible to count all the cater- 

 pillars eaten by a bird during its visit, for it was likely to 

 be partially hidden from the observer a part of the time by 

 twigs or leaves. The results given show only the number 

 of caterpillars each bird was actually seen to eat. The ob- 

 server in many instances notes that the bird must have eaten 

 many more, as it was almost continually eating during its 

 visit. 



To prepare the reader for the somewhat startling facts 

 which follow, it is necessary to consider some of the physio- 

 logical characteristics of the bird. Birds as a class are among 

 the most highly organized of vertebrate animals. In this class 

 we find the extreme of activity and the highest temperature 

 of the blood. Their remarkable activity, especially in flight, 

 causes a tremendous waste of tissue. To supply the waste 

 caused by this great expenditure of nervous energy a large 

 quantity of food is required. Nature has made ample pro- 

 vision for the digestion and assimilation of this great quan- 

 tity of food, supplying the bird with a remarkably perfect 

 digestive apparatus, the action of which is very rapid. The 

 writer has recorded elsewhere the results of experiments with 

 two crows, which show that the food passes through the entire 

 digestive tract in about one and one-half hours, and it is known 

 that digestion is much more rapid in some of the smaller 

 insect-eating birds. The amount of food required by the 

 crow is given by Mr. E. A. Samuels as eight ounces per day. 

 In readins: what follows one should take into consideration 

 not only the enormous amount of food required daily by the 

 birds, but also note the dates on which the observations were 

 made. It would seem impossible for some of the smaller 

 birds mentioned to stow away in their small stomachs so 

 many caterpillars in so short a space of time. But the dates 

 alone will indicate to those familiar with the life histories of 

 the insects that where the greater numbers were eaten the 

 caterpillars were quite small, and such is the fact. 



The facts given below were ascertained by Messrs. Mosher 

 and Kirkland : — 



