THE PRACTICAL VALVE OF BIRDS. 35 



Two orchard orioles from a canker-infested orchard contained canker 

 worms 77%, other caterpillars 20%, ants 3% (141), while 11 from elsewhere 

 contained insects 91%, vegetation 9%, nearly all mulberry (142). 



Bobolinks are said to do $2,000,000 damage annually to southern rice 

 fields, but in their northern breeding grounds they are more than half 

 insectivorous, taking 90% of injurous insects in June (143). 



FringUlidae. This family, including over 12% of the bird species of 

 the United States, is essentially a family of seed-eaters, but they take many 

 insects in summer and many of them feed their young at first almost entirely 

 on insects. Stomachs of the goldfinch, dickcissel, grasshopper sparrow, 

 chipping sparrow, field sparrow, rose-breasted grosbeak and indigo bunting 

 from a canker-infested orchard contained an average of 91% of insects, 

 40% being canker worms (144). Two pine siskins contained 1,900 black olive 

 scales and 300 plant lice 1 , and in one green-backed goldfinch there were 300 

 plant lice (145). 



Half of the food of the rose-breasted grosbeak, two-thirds of that of the 

 black-headed and blue grosbeaks, one-fourth of that of the gray grosbeak 

 and cardinal, consists of insects, the balance largely weed seeds, while the 

 nestlings of all are fed at first entirely upon insects (146). Probably the pine 

 grosbeak of our higher Colorado mountains lives largely on conifer seeds, 

 but Aughey found many locust eggs in five stomachs (146-a). The western 

 evening grosbeaks, which come to Boulder every winter, feed almost entirely 

 upon box elder seeds while here, so far as I have observed. 



California and Anthony's towhees, 399 stomachs, insects 14%, weed seeds 

 51%, grain 28%. Spotted towhees (Pipilo maculatus and subspecies), 139 

 stomachs, insects about 30%, weed seeds 34%, grain 4.7%, mast 15.6%, 

 .fruit 17.7% (147). 



Insects form on an average 25% of the food of our native sparrows 

 and finches, for the year, and weed seeds 50% for the year, the latter item 

 rising to 80% in the cold half of the year, the value of the sparrows being 

 "greater than that of any other group of birds whose economic status has 

 thus far been investigated." It is estimated that by the destruction of weed 

 seeds these birds save $89,260,000 annually to' the farmers. Visits to the 

 field will often show that nine-tenths of the weed seeds produced have been 

 destroyed by these birds (148). 



In June 93% of the food of the chipping sparrow is insects, and 38% 

 for the year (149). Stomachs of 500 slate-colored juncoes contained weed 

 seeds 61.8%, grain 8%, insects 24% (150). Beal (151) estimated that the 



(141) Forbes, 111. St. Lab. Nat. Hist., Bull. Vol. I, No. 3, p. 14. 



(142) Judd, U. S. Biol. Surv., Bull. No. 17, p. 96. 



(143) Beal, Ibid., Bull. 13, pp. 12-22 ; Farmers' Bull. No. 54, p. 17. 



(144) Forbes, 111. St. Lab. Nat. Hist., Bull., Vol. I, No. 6, p. 13. 



(145) Beal, U. S. Biol. Surv., Bull. 34, pp. 73-75. Farmers' Bull. No. 513, p. 5. 



(146) McAtee, Food Habits of the Grosbeaks, U. S. Biol. Surv., Bull. No. 32 ; Our 

 Grosbeaks and their value to Agriculture, Farmers' Bull. No. 456. Beal, U. S. Biol. 

 Surv., Bull. No. 34, pp. 93-96. 



(146-a) Aughey, First Kept. II. S. Entom. Comm., App. II, p. 28. 



(147) Beal, U. S. Biol. Surv., Bull. 34, pp. 86-93. 



(148) Judd, The Relation of Sparrows to Agriculture, U. S. Biol. Surv., Bull. No. 

 15, pp. 7, 11, 28-29 ; Birds as Weed Destroyers, U. S. Dept. Agric., Yearbook for 1898, 

 D *223 Farmers' Bull. No. 513, p. 4. 



(149) Judd, Ibid., Bull. 15, p. 78. Weed, An Observation of the Feeding Habits 

 of the Chipping Sparrow, N. Hamp. Coll., Agric. Experiment Sta., Bull. No. 55, pp. 



(150) Beal and McAtee, U. S. Dept. Agric., Farmers' Bull. No. 506, pp. 26-28. 



(151) Beal, Farmers' Bull. No. 54, p. 28. 



