THE ALLIES OF THE PIGEON: AVES 393 



the economic conditions of a single area. The tract chosen 

 was a farm of about two hundred and thirty acres on the 

 Potomac River in Maryland, just opposite Mount Vernon. 

 Here observations were made on the bird and insect life of the 

 farm, with the view of determining not only what the birds 

 really did eat but also what food was available for them at 

 different seasons. So, too, the vertebrate life of the farm, 

 the mice, poultry, and game, which form a part of the food 

 of some birds; the fruit, both wild and cultivated; the grain 

 and the weeds of the region, and the crops that were planted ; 

 all these were considered in the investigation. Besides obser- 

 vations on the living birdsJflhe stomachs of six hundred and 

 forty-five specimens were examined. As in other investiga- 

 tions along the same line, it was found that the largest con- 

 sumption of insects is to be credited not to the adult but to 

 the nestling. As several broods are raised by many birds 

 each year, and each young bird requires at first considerably 

 more than its own weight of food in a day, the number of 

 insects destroyed in this way is almost incalculable. Of course 

 some beneficial insects are included in this list, but it has 

 been found that those insects which are to be classed as cer- 

 tainly useful, as some of the bees, wasps, and beetles, which 

 prey on pests, make up a very small proportion of the food. 

 The diagram (Fig. 208) shows the proportion of different sorts 

 of food in the young and the adult of the common crow. 



Some of the conclusions of Dr. Judd, who studied this region 

 for the Biological Survey, are that " the English sparrow, the 

 sharp-shinned and Cooper hawks, and the great horned owl 

 are, as everywhere, inimical to the farmers' interests and 

 should be killed at every opportunity. The sapsucker punc- 

 tures orchard trees extensively and should be shot. The 

 study of the crow is unfavorable in results so far as these 

 particular farms are concerned, partly because of special con- 

 ditions. Its work in removing carrion and destroying insects 



