36 FUNDAMENTALS OF AGRICULTURE. 



Necessity for Birds. Huxley tells us that were the 

 increase of a species of aphis (a small insect) to go 

 on unchecked the progeny of a single female in one 

 year would equal in bulk the population of the Chi- 

 nese Empire. Birds operate to prevent this increase. 

 Many instances are on record where birds, gathering 

 from far and near, have saved trees or crops from de- 

 struction by insects or other pests. If the birds were 

 all destroyed and their repressive influence on the in- 

 crease of insect life thus removed, an unparalleled in- 



Nestling. Adult. 



FOOD OF CUCKOO. 



I, Spider; 2, stink-bug; 3, May-beetle; 4, grasshopper; 5, caterpillar; 6, cut-worm. 



crease of insects might be expected to follow. The 

 local destruction and extirpation of birds has been fol- 

 lowed in all recorded cases by an increase of pests, a 

 consequent serious injury to vegetation, and even at 

 times by famine among the inhabitants. 



The Food of Birds. The investigations regarding 

 the food of birds made by the Bureau of Biological 

 Survey of the United States Department of Agricul- 

 ture have proved conclusively that birds feed very 

 largely on many of the most destructive insects of 

 farm, field and forest, as well as on the seeds of per- 

 nicious weeds. The capacity birds show for such food 



