CHAPTER V. 

 THE AMOUNT OF FOOD CONSUMED BY BIRDS. 



BIRDS as a class are the most active members of the ani- 

 mal kingdom. They have rapid circulation and respiration ; 

 are constantly on the alert during all seasons of the year; 

 travel long distances in migrating or searching for food ; rear 

 large families, often two or more broods in a summer ; and, in 

 short, perform for their size a prodigious amount of work. 

 Because of this, one would expect them to require a large 

 amount of food to keep up the energy they are so constantly 

 expending, and the studies that have so far been made show 

 that such is emphatically the case. 



Unfortunately, the problem of ascertaining just how much 

 food wild birds need presents many difficulties in the way of 

 its solution. So long as birds are at liberty, evidence must 

 always be fragmentary and often uncertain. When they are 

 kept in captivity, natural conditions are upset : the worry of 

 confinement, the lack of exercise, and a changed diet are fac- 

 tors of more or less importance ; we can scarcely say how 

 much. With nestlings the matter is simpler, though much 

 time and patience and common sense are necessary in order 

 to obtain creditable results. 



Thus, it is not to be wondered at that in the whole mass of 

 ornithological literature which latterly has increased to very 

 respectable proportions there is a striking paucity in this 

 line. It is to be hoped that the gap will not be allowed to 

 exist very much longer, as reliable data on the amount of food 

 consumed is in economic importance second only to the kind 

 consumed. Although information is scarce, yet there is 

 enough to demonstrate that the quantity of food eaten by 

 birds is relatively much greater than that consumed by any 

 other class of vertebrates. 



59 



