54 NEBRASKA STATE HORTICULTURAL SOCIETY. 



round numbers about 75,000,000 of birds. If, as has been estimated, 

 tliree-fourtlis of the food of this host of l)irds shoukl consist of in- 

 sects, what would this mean? A very conservative estimate as to the 

 number of insects eaten daily by each bird can be set down at twenty- 

 five.* This being true, it would take one billion eight hundred and 

 seventy-five millions of insects for a single day's rations for our birds 

 during any one of the 175 days of summer. If these insects were 

 spread out at the average of ten thousand to the acre, a day's work of 

 our birds would mean the complete clearing of 18,750 acres. 



Professor Forbes says: "On this basis, if the operations of the 

 birds were to be suspended, the rate of increase of these insect hosts 

 would be accelerated about seventy per cent, and their numbers, in- 

 stead of remaining year by year at the present average figure, would 

 be increased over two-thirds each year. Any one familiar with geo- 

 metrical ratios will understand the inevitable result. In the second 

 year we should find insects nearly three times as numerous as now, 

 and in about twelve years if this increase were not otherwise checked, 

 we should have the entire state carpeted with insects, one to the square 

 inch over our whole territory." f What would be true in Illinois 

 would apply equally well for Nebraska. 



More than twenty-five years ago Benjamin Walsh, the first state 

 entomologist of Illinois, estimated the damage done by insects in that 

 state at twenty million dollars annually. Again splitting these fig- 

 ures in the middle and allowing only half as much for our state, or 

 ten million dollars. Supposing that by some means or other we could 

 increase tlie efficiency of our birds only one per cent, the saving that 

 would result could be plainly set down at $100,000. This increase in 

 the efficiency of our birds, like all other estimates, is very low. Sup- 

 posing it should be five per cent instead, then the saving would be an 

 even half million dollars annually. The si)aring of a single bird an- 

 nually for each inhabitant of the state would more than meet the above 

 estimates. 



Even if birds do destroy alike the injurious and the parasitic insects, 



* These figures, large as they seem, are much too small. Most birds eat at least 

 two meals each day, and the stomach contents of all birds examined by those en- 

 {ra'^ed in the stndy of their food-habits would indicate that seventy-five or a hun- 

 dred insects per day would be more nearly correct. 



t Bulletin of the Illinois .State Laboratory of Natural History. Vol. I, No. 3, 

 p. 81. 



