34 CIVIC BIOLOGY 



seeds. Both classes, however, feed the young mainly on in- 

 sects. Our gardens, fields, and roadsides are weedy enough, 

 but who can imagine what they would be, were not thousands 

 of tons of weed seeds destroyed annually by the sparrows, 

 bobwhites, doves, larks, blackbirds, and others. About fifty 

 species of birds are efficient weed destroyers. Compare and 

 draw a few typical hard and soft bills to fix this distinction. 

 Beal has estimated that the tree sparrows alone in the state of 

 Iowa destroy annually about 875 tons of weed seed. Are both 

 weeds and seed-eating birds abundant in your bird tract ? 



Hawks, owls, and shrikes render service in destroying noxious 

 mammals. Are the mice, rats, field-mice, or gophers numerous 

 in your district, and what amount of damage do they cause 

 by eating grain or girdling trees ? Dr. C. Hart Merriam has 

 estimated that a bounty act on hawks and owls, during its 

 operation in Pennsylvania for a year and a half, cost the state 

 not less than $4,000,000. 



The accompanying food chart shows about all we know of 

 the foods of many of our commonest species. The blank 

 squares in the chart indicate generally deficiencies in observa- 

 tion, and not that any particular bird does not eat any par- 

 ticular insect ; hence they are in reality the most interesting 

 part of the chart because they suggest further study. Observe 

 the birds in your district, or, if you have a young or disabled 

 bird, make definite feeding tests and record the results in your 

 food chart. The chart will thus enable you to feed intelligently 

 many birds that come to hand, and also to add to our knowl- 

 edge of the subject. The probable diet of any bird not named 

 on the chart may be judged from that of its near relatives. 1 



1 The authors would be grateful if those who make such feeding tests 

 would send them any data secured. 



