l88 BOARD OF AGRICULTURE. [Jan., 



these uprisings soon become apparent because of the injury 

 they do. Birds would ordinarily hold in check all insects 

 which they eat with avidity were it not (i) that the birds have 

 been much reduced in numbers; (2) that man in planting and 

 cultivating crops makes conditions favorable for the propaga- 

 tion of insects and unfavorable to the increase of birds. Many 

 species of birds, especially game birds, are gradually disappear- 

 ing; a few are extinct. The farmer, by devoting large areas 

 to a special crop, and growing the same crops year after year, 

 offers the insects that infest those crops a splendid opportunity 

 to multiply, wdiile the cultivation of the field drives out the 

 birds that formerly nested there. 



Birds are remarkably active and energetic creatures, having 

 a high temperature, rapid circulation and respiration, and re- 

 quiring a tremendous amount of food to sustain their activity 

 and repair the waste of the tissues. 



Some of the smaller birds require only half an hour to an 

 hour and a half to digest a full meal, and the stomach is filled 

 many times each day. The rapidly growing young need far 

 more food in proportion to their size than do the old birds. 

 An adult crow will eat from five to eight ounces of food daily. 

 A young crow, nearly fledged, requires about ten ounces. Pro- 

 fessor Treadwell found that a young robin needed, daily, a 

 quantity of beef equal to one-half its own weight, or forty- 

 eight per cent, more than its own weight in worms, to secure its 

 healthy growth and development. Where insects are numerous, 

 birds eat them with almost incredible rapidity. INIy assist- 

 ant, Mr. F, H. Mosher, saw a pair of tanagers eat thirty-five 

 newly hatched caterpillars in a minute. They continued eating 

 these minute insects at this rate for eighteen minutes ; so that, 

 if Mr. Mosher's count is correct, they must have eaten in this 

 short time six hundred and thirty of the little creatures. This 

 would not make them a full meal, as the entire number would 

 hardly be equal in bulk to one full-grown caterpillar. By care- 

 fully watching two yellowthroats, and counting the plant-lice 

 they ate, he estimated that they destroyed seven thousand 

 within an hour, — a thing almost incredible, but still possible, 

 when we consider the exceedingly small size of the insects 

 at the time, their swarming numbers, the activity of the chicka- 

 dee, and its remarkably rapid digestion. Dr. Judd speaks 

 of a letter received from Mr. Robert H. Coleman, in which he 



