212 KEPORT UPON COTTON INSECTS. 



Among the vertebrate enemies, it will be of interest in this connection 

 to be able to form an idea of the actual number of insects destroyed by 

 the average insectivorous bird. As concise a statement of facts upon 

 this point as we have met with is given in Professor Aughey's report to 

 the United States Entomological Commission, from which we have already 

 quoted in the early part of this chapter.* Professor Aughey says : 



Few unobservant people have any comprehension of the vast number of insects that 

 birds actually destroy. During the breeding-season this destruction of insects by birds 

 reached its culmination. The young of some species will eat. about 50, others about 

 60, some about 75 insects each day. The average cannot be far from 60. At this rate 

 rive young birds would eat about 300 insect each day, or about 9,000 a month for each 

 month, exclusive of the parents. There have been widely different estimates as to the 

 number of insects that the old birds eat, but it ought not to be difficult to approximate 

 the quantity. Only a small part of a bird's stomach is entire enough to be distin- 

 guished and counted. If the balance is composed as largely of insects, which is more 

 than probable, then the whole number eaten during a day by an insectivorous bird 

 must be near 200. I reached the same conclusion by actual tests. In the fall of 1874 

 I bought two Bartramian plovers from some boys who had trapped them, and kept them 

 for a week in a cage before they were set free. I fed them on locusts and other insects, 

 which I counted for four days with the following result : 



First day 277 



Second day 452 



Third day 448 



Fourth day 439 



Total 1,616 



Average per day 404 



Average for each 202 



I was compelled to go away or else the experiment would have been continued 

 longer. 



About one-fourth of the insects were locusts, and the balance were flies, ants, beetles, 

 &c. I gave them whatever insects the boys that I hired gathered for me. My im- 

 pression, however, is that they ate less than they would have done if they had been 

 at liberty. But, lest there might tte some mistake, and to avoid all possibility of error 

 on the wrong side, we will base our calculations on an estimate of 150 insects each day 

 for a mature plover. At this rate 20 old plovers would eat 3,000 insects each day, or 

 90,000 a month. And suppose further that these 20 plovers had nests which averaged 

 four young ones each. At 60 insects a day for each young plover the 40 would con- 

 sume 2,400 every twenty-four hours, or 72,000 a month. The 20 plovers and their 

 progeny together would consume 162,000 insects each month. At this same rate 1,000 

 plovers and their young would consume in one month 8,100,000 insects. That many 

 insects removed in one year from a farm of 160 acres would probably render it capable 

 of producing crops even when these insects were doing their worst. As there are many 

 birds that eat more insects than do the plovers, as well as many that eat less, 150 in- 

 sects a day is probably a fair average for all insectivorous birds. 



This extract is eloquent as a defense of birds and puts us on a sound 

 basis of apparently unexaggerated facts. Too much, then, can hardly 

 be said in favor of insectivorous birds in cotton-fields. We have entered 

 into the English-sparrow question somewhat at length. Every day brings 

 confirmatory evidence in support of the conclusions at which we have 



* First annual report of the United States Entomological Commission, 1877. Rocky 

 Mountain Locust, Department Interior, 1878. 



